Association between subclinical hypocalcemia in the first 3 days of lactation and reproductive performance of dairy cows

Association of different classifications of hypocalcemia with quantity and quality of colostrum, milk production, and health of Holstein dams and their calves

The aim of the present study was to assess the effect of serum calcium (Ca) status in the early postpartum period on the quantity and quality of colostrum, milk production, and the health of Holstein dams and their calves. One hundred multiparous Holstein cows were enrolled in this study. To determine serum Ca status, blood samples were taken at 1 and 4 days in milk (DIM). Cows were categorized into 1 of 4 groups based on their serum Ca concentrations: normocalcemic (CON; Ca >1.87 at 1 DIM and >2.10 mmol/L at 4 DIM, n = 36), transient SCH (TSCH; Ca ≤1.87 at 1 DIM and >2.10 mmol/L at 4 DIM, n = 14), persistent SCH (PSCH; Ca ≤1.87 at 1 DIM and ≤2.10 mmol/L at 4 DIM, n = 15), or delayed SCH (DSCH; Ca >1.87 at 1 DIM and ≤2.10 mmol/L at 4 DIM, n = 35). The ROC curve was utilized to determine the optimal cut-off value for serum total Ca, maximizing both sensitivity and specificity in predicting metritis. Metabolic disorders such as dystocia, retained placenta, and culling within 60 DIM were not affected by serum Ca status in the early postpartum period (P > 0.10). However, the incidences of metritis and endometritis were different based on the serum Ca status of the cows. The PSCH cows had a higher incidence of metritis than the CON cows (P = 0.05). Also, the DSCH cows tended to have an increased risk of metritis than the CON cows (P = 0.09). However, metritis incidence in the TSCH and CON cows was similar (P = 0.83). Cows with PSCH (P = 0.07) and DSCH (P = 0.10) tended to be at a higher risk for endometritis than the CON cows. But, the incidence of endometritis in the TSCH and CON cows was not different (P = 0.50). The TSCH cows had higher milk yield than the PSCH and DSCH cows (P = 0.05). However, milk yield was not different between the TSCH and CON cows and the PSCH and DSCH and CON cows. The serum Ca status of cows had no effect on colostrum volume and its quality, age and weight of weaning, and average daily gain of calves (P > 0.10). The proportion of calves experiencing failure of passive transfer (FPT) was greater in the PSCH group than in the CON group (P = 0.03). Also, the FPT tended to be higher in the DSCH calves compared to the CON calves (P = 0.10). However, the FPT in the TSCH and CON calves was not different (P = 0.83). The incidence of diarrhea tended to be higher in the PSCH and DSCH calves compared to the CON calves (P = 0.10). However, diarrhea incidence between the TSCH and CON calves was similar (P = 0.97). Overall, the findings of this study suggest that cows with TSCH showed better adaptation to lactation, experienced a lower occurrence of diseases and produced higher milk compared to PSCH and DSCH cows. Furthermore, despite the similar quantity and quality of colostrum across all groups, the PSCH and DSCH groups displayed a greater proportion of calves experiencing FPT and diarrhea in comparison to the TSCH group.

Association between non-esterified fatty acids and calcium concentrations at calving with early lactation clinical diseases, fertility and culling in grazing dairy cows in Uruguay

This study describes the association of non-esterified fatty acids (NEFA) and calcium concentrations at calving with early lactation disease, reproductive performance and culling in 646 dairy cows from 13 commercial grazing dairy herds in Uruguay. During one year, health events were recorded from calving to 30 days in milk (DIM). The first author visited each farm every 20 days. During each visit, body condition score (BCS) was recorded (scale 1-5), defining BCS < 3 as suboptimal and BCS > 3 as optimal, and a blood sample was taken from cows between 0 and 4 DIM for metabolite determination. To evaluate the association between health events (i.e., retained placenta-metritis and clinical mastitis) and risk factors (parity, BCS, high NEFA (> 0.6 mmol/L) and subclinical hypocalcemia (SCH) (< 2.10 mM)) data were analysed using multivariable logistic regression models. To evaluate the association of health events and risk factors with reproductive performance and culling, data were analysed using Cox proportional hazard regression models. A risk factor and an outcome of interest were assumed to be associated at P < 0.05 and a tendency to be associated was defined at P < 0.10. Overall, 47 % (n = 303) of the cows showed elevated NEFA concentration and 77 % (n = 499) had SCH. In addition, 21.5 % (n = 139) of the cows recorded at least one clinical disease. Cumulative incidence was 17 % (n = 109) for clinical mastitis, 4.2 % (n = 27) for retained placenta (RP)-metritis and 1.4 % (n = 7) for lameness. Clinical mastitis was associated with parity, with lower odds in primiparous (PP) cows (OR = 0.42, P < 0.01). Cows in an optimal BCS also tended to have lower odds (OR = 0.66, P = 0.07). Moreover, high NEFA and SCH cows had higher odds of CM (OR = 4.5, P = 0.01 and OR = 1.75, P = 0.04, respectively). Retained placenta-metritis tended to be associated with high NEFA concentration (OR = 2.2, P = 0.06). Primiparous cows with suboptimal BCS showed an increased first insemination rate (HR = 2.34; P < 0.01). The risk of culling was lower in PP cows (HR = 0.19; P < 0.01) and in cows with optimal BCS and low NEFA concentration (HR = 0.38; P = 0.03). Our data show that metabolic challenge (defined as peripartum suboptimal BCS, high NEFA or SCH) is associated with increased odds of clinical mastitis and RP-metritis, decreased probability of insemination and increased hazard of culling. Under grazing conditions, we suggest that farm management to improve the metabolic adaptation to lactation represents an opportunity to enhance cow performance in terms of health, fertility and longevity.

Does knowledge of blood calcium concentration at 2 days postpartum affect decisions of calcium supplementation?

Delaying oral Ca supplementation might benefit cows with low blood Ca concentrations at 4 d in milk (DIM), a time when reduced blood total Ca (tCa) is associated with negative health and production outcomes. To implement a targeted approach to manage subclinical hypocalcemia (SCH) at the herd level, it is important to identify which cows benefit from supplemental Ca. Therefore, our objective was to determine if SCH diagnosis at 2 DIM could inform decisions of oral Ca supplementation at 2 and 3 DIM based on milk yield and 4 DIM blood Ca concentration. Data were analyzed from a previously conducted randomized controlled trial on multiparous cows (n = 518) from 4 farms in New York State. Cows were randomly assigned to 1 of 2 treatment groups at calving: (1) control (CON; no Ca supplementation, n = 259) or (2) bolus (BOL; 43 g of oral Ca administered at 2 and 3 DIM postcalving, n = 259). For each parity group (2, 3, 4+), we used generalized linear mixed models to identify serum tCa concentrations at 2 DIM that maximized the difference in milk yield to diagnose SCH. Cows were classified as normocalcemic (NC; parity 2 tCa >1.9 mmol/L, parity 3 tCa >1.87 mmol/L, n = 327; parity ≥4 had no defining threshold) or SCH (parity 2 tCa ≤1.9 mmol/L, parity 3 tCa ≤1.87 mmol/L, n = 58; parity ≥4 had no defining threshold). Parity 2 and 3 cows were further classified into 1 of 4 SCH-treatment groups (SCHTRT) based on 2 DIM SCH status and random treatment allocation: (1) NC-CON, n = 165, (2) SCH-CON, n = 28, (3) NC-BOL, n = 162, or (4) SCH-BOL, n = 30. Generalized linear mixed models were used to analyze the difference in milk yield for the first 10 wk of lactation and tCa at 4 DIM between SCHTRT groups with separate analyses performed for parities 2 and 3. Mean milk yield differed between SCHTRT groups for both parities. For parity 2, SCH-CON and SCH-BOL cows produced more milk than NC-CON and NC-BOL cows with SCH-CON producing 50.9 (95% confidence interval [CI] = 48.4, 53.4) kg/d, SCH-BOL 51.7 (49.1, 54.2) kg/d, NC-CON 47.5 (46.3, 48.7) kg/d, and NC-BOL 47.2 (45.8, 48.5) kg/d of milk. Milk yield was also different between SCHTRT groups for parity 3 with SCH-BOL cows producing more milk than NC-CON and NC-BOL cows. In parity 3, SCH-BOL cows produced 56.3 (95% CI = 53.1, 59.3) kg/d, SCH-CON 51.7 (48.6, 54.7) kg/d, NC-BOL 50.6 (49.0, 52.2) kg/d, and NC-CON 48.7 (46.9, 50.5) kg/d of milk. For both parities, SCH-CON and SCH-BOL cows had lower tCa at 2 DIM than NC-CON and NC-BOL cows. At 4 DIM, tCa concentrations were similar for all SCHTRT groups respective to parity. Our results suggest that although delayed Ca bolus administration does not improve blood Ca concentration when compared with controls, it does support increased milk production in parity 3 cows regardless of Ca status at 2 DIM. Thus, knowledge of blood Ca at 2 DIM should not affect decisions of Ca supplementation in this parity of cows.

Associations of postpartum health with progesterone after insemination and endocrine signaling during early pregnancy in dairy cows

Our objective was to investigate associations of postpartum health with serum progesterone (P4) concentrations after first artificial insemination (AI), expression of interferon-stimulated genes (ISG) in blood leukocytes, and serum pregnancy-associated glycoprotein (PAG) during early pregnancy in dairy cows. In this observational study, Holstein cows (n = 475) from 2 commercial herds were enrolled 3 wk before expected parturition. Body condition score (BCS) and lameness were assessed at enrollment, and total Ca, haptoglobin, and nonesterified fatty acids (NEFA) were measured in serum at 2 and 6 ± 2 d in milk (DIM). Blood β-hydroxybutyrate and metritis were evaluated at 4, 8, 11, and 15 ± 2 DIM, and purulent vaginal discharge (PVD) and endometritis based on endometrial cytology were diagnosed at 35 DIM. Onset of cyclicity was assessed by biweekly P4 measurements. The BCS was assessed at enrollment and at 63 DIM, and lameness at enrollment and at 21 and 49 DIM. First AI was based on estrus detection until ∼75 DIM, or synchronization for timed AI thereafter. Serum P4 was measured at d 8 and 12 after first AI; expression of ISG (ISG15 and RTP4) in blood leukocytes was assessed at d 19; and PAG in serum of pregnant cows was measured at d 29, 33, and 40. Multivariable linear regression models were built including health variables (with metabolites categorized via receiver operating characteristic curve analysis) and covariates (season, milk yield, AI method, DIM), accounting for pregnancy status (for ISG and PAG models), repeated measures (for P4 and PAG models), and herd as random. Results are reported comparing cows affected versus unaffected by each predictor. Serum P4 concentrations were lesser at d 8 after AI in cows that had total Ca ≤2.09 mM (3.6 vs. 4.0 ± 0.2 ng/mL) at 2 DIM or a clinical disease (3.7 vs. 4.0 ± 0.2 mg/mL), and P4 tended to be lesser at d 8 in cows that had PVD (3.6 vs. 4.0 ± 0.2 ng/mL) or any uterine disease (3.7 vs. 4.1 ± 0.2 ng/mL). Among cows pregnant at d 29, relative ISG15 expression (fold change) at d 19 was greater in cows that had lameness (5.10 [4.18-6.18] vs. 3.14 [3.10-3.19]) but tended to be lesser in cows that had endometritis (3.20 [2.89-3.54] vs. 4.29 [4.20-4.35]), and relative expression of RTP4 tended to be lesser in cows that had displaced abomasum (1.02 [0.62-1.67] vs. 1.75 [1.73-1.78]). Serum PAG was lesser at d 29 (3.8 vs. 4.2 ± 0.2 sample-to-positive ratio [S:P]) in cows that had NEFA ≥0.73 mM at 6 DIM, and lesser at d 33 (3.9 vs. 4.5 ± 0.2 S:P) and 40 (3.1 vs. 3.7 ± 0.2 S:P) in cows that had prepartum BCS ≥3.75. These findings suggest long-term effects of metabolic or reproductive tract disorders on luteal function after first AI, pregnancy recognition signaling, and placental function during early pregnancy. These associations may partially explain some of the pathways linking postpartum health and fertility in dairy cows.

Interaction of blood calcium with milk yield, energy metabolites, subclinical mastitis, and reproductive performance in crossbred dairy cows

Limited literature is available on the consequences of postpartum low blood calcium (Ca) concentration in crossbred cows. The research aimed to investigate the correlation between postpartum serum Ca levels and various parameters, including milk yield, serum energy metabolites, milk somatic cell count, and reproductive factors in crossbred cows. Following parturition, a total of 45 potential high-yielding F2 (HF × Sahiwal; Genotype: 75:25) dairy cows were enrolled . These cows were categorized based on plasma calcium concentrations into three groups: a low calcium group (Ca-L) with a calcium concentration of <5 mg/dL, a medium calcium group (Ca-M) with a calcium concentration ranging from 5 to 8.5 mg/dL, and a high calcium group (Ca-H) with a calcium concentration exceeding 8.5 mg/dL. The study parameters were measured over an 8-week period. The results indicated that overall milk yield and blood glucose were significantly higher in the Ca-H group compared to Ca-M and Ca-L (p < .01). Blood cholesterol was significantly higher in Ca-M (p < .01), while blood triglyceride was significantly lower in both Ca-M and Ca-H. Overall, blood cortisol did not show a significant change between these groups (p < .01); however, progesterone levels were higher (p < .01) in Ca-M and Ca-H cows. Furthermore, somatic cell count (SCC) significantly (p < .01) decreased in cows with Ca-H compared to Ca-L. Additionally, postpartum oestrous interval and interestrus interval decreased significantly (p < .01) in Ca-M and Ca-H compared to Ca-L. These findings suggest that cows with blood calcium levels exceeding 8.5 mg/dL exhibited significantly higher milk yield, blood metabolite levels, a lower likelihood of subclinical mastitis, and earlier reproductive activity after calving.

The Most Important Metabolic Diseases in Dairy Cattle during the Transition Period

This review paper provides an in-depth analysis of three critical metabolic diseases affecting dairy cattle such as subacute ruminal acidosis (SARA), ketosis, and hypocalcemia. SARA represents a disorder of ruminal fermentation that is characterized by extended periods of depressed ruminal pH below 5.5-5.6. In the long term, dairy herds experiencing SARA usually exhibit secondary signs of the disease, such as episodes of laminitis, weight loss and poor body condition despite adequate energy intake, and unexplained abscesses usually 3-6 months after an episode of SARA. Depressed milk-fat content is commonly used as a diagnostic tool for SARA. A normal milk-fat test in Holstein dairy cows is >4%, so a milk-fat test of <3% can indicate SARA. However, bulk tank testing of milk fat is inappropriate to diagnose SARA at the herd level, so when >4 cows out of 12 and <60 days in milk are suspected to have SARA it can be considered that the herd has a problem. The rapid or abrupt introduction of fresh cows to high-concentrate diets is the most common cause of SARA. Changes in ruminal bacterial populations when exposed to higher concentrate rations require at least about 3 weeks, and it is recommended that concentrate levels increase by no more than 400 g/day during this period to avoid SARA. Ketosis, a prevalent metabolic disorder in dairy cattle, is scrutinized with a focus on its etiological factors and the physiological changes leading to elevated ketone bodies. In total mix ration-fed herds, an increased risk of mastitis and reduced fertility are usually the first clinical signs of ketosis. All dairy cows in early lactation are at risk of ketosis, with most cases occurring in the first 2-4 weeks of lactation. Cows with a body condition score ≥3.75 on a 5-point scale at calving are at a greater risk of ketosis than those with lower body condition scores. The determination of serum or whole blood acetone, acetoacetate, beta-hydroxybutyrate (BHB) concentration, non-esterified fatty acids (NEFA), and liver biopsies is considered the best way to detect and monitor subclinical ketosis, while urine or milk cowside tests can also be used in on-farm monitoring programs. Concentrations >1.0 mmol/L or 1.4 mmol/L blood or serum BHB are considered diagnostic of subclinical ketosis. The standard threshold used for blood is 1.2 mmol/L, which corresponds to thresholds of 100 mcmol/L for milk and 15 mg/dL for urine. Oral administration of propylene glycol (250-400 g, every 24 h for 3-5 days) is the standard and most efficacious treatment, as well as additional therapy with bolus glucose treatment. Hypocalcemia is a disease of adult dairy cows in which acute hypocalcemia causes acute to peracute, afebrile, flaccid paralysis that occurs most commonly at or soon after parturition. Dairy cows are at considerable risk for hypocalcemia at the onset of lactation, when daily calcium excretion suddenly increases from about 10 g to 30 g per day. Cows with hypocalcemia have a more profound decrease in blood calcium concentration-typically below 5.5 mg/dL. The prevention of parturient paresis has been historically approached by feeding cows low-calcium diets during the dry period. Negative calcium balance triggers calcium mobilization before calving and better equips the cow to respond to the massive calcium needs at the onset of lactation. Calcium intake must be limited to <20 g per day for calcium restriction to be effective. The most practical and proven method for monitoring hypocalcemia is by feeding cows an acidogenic diet for ~3 weeks before calving. Throughout the review, emphasis is placed on the importance of early diagnosis and proactive management strategies to mitigate the impact of these metabolic diseases on dairy cattle health and productivity. The comprehensive nature of this paper aims to serve as a valuable resource for veterinarians, researchers, and dairy farmers seeking a deeper understanding of these prevalent metabolic disorders in dairy cattle.

Effects of timing of oral calcium administration on milk production in high-producing early-lactation Holstein cows

Supplementation of oral Ca via blanket administration of an oral Ca bolus at 0 and 24 h after calving has shown limited success in increasing production and minimizing adverse health events. Recent evidence that reductions in blood Ca at 4 d in milk (DIM) are more closely associated with negative outcomes than hypocalcemia at 0 to 24 h postpartum might explain this lack of Ca bolus efficacy. Therefore, our primary objective was to explore the effect of delayed oral Ca bolus supplementation on milk production, with secondary objectives of exploring the effects on disease incidence and postpartum blood Ca dynamics. We conducted a randomized controlled trial on multiparous Holstein cows (n = 998) from 4 herds in New York. At calving, cows were randomly assigned to 1 of 3 treatment groups: (1) control, no supplemental Ca at or around parturition (CON; n = 343); (2) conventional bolus, an oral Ca bolus containing 43 g of Ca at calving and 24 h later (BOL-C; n = 330); or (3) delayed bolus, an oral Ca bolus containing 43 g of Ca at 48 and 72 h after calving (BOL-D; n = 325). We created generalized linear mixed models to analyze differences in milk yield for the first 10 wk of lactation and serum total Ca (tCa) at 1 and 4 DIM between treatment groups; multivariable Poisson regression models were used to analyze adverse event outcomes (metritis, displaced abomasum, herd removal, or a combination of one or more of the 3) in the first 30 DIM. Milk yield increased by week and was not affected by treatment. However, a treatment by parity group interaction for milk yield showed that BOL-D cows in the third parity produced more milk than third-parity BOL-C or CON cows (BOL-D = 52.0 kg/d, 95% confidence interval [50.6, 53.4] kg/d, BOL-C = 47.9 [46.3, 49.5] kg/d, CON = 49.8 [48.2, 51.2] kg/d). The incidence of adverse health events was similar between treatments (BOL-D = 3.7%, BOL-C = 3.7%, CON = 3.6%). Serum tCa was lower at 1 than 4 DIM, and we detected no difference in tCa between treatment groups. Our findings suggest that delaying oral Ca bolus supplementation has limited influence on blood Ca concentrations but may be beneficial to cohorts of cows as a targeted prophylactic supplement to support milk production.

Circulating parathyroid hormone and serotonin in multiparous cows with differing postparturient serum calcium concentrations

Many multiparous dairy cows experience subclinical hypocalcemia (SCH) in the immediate postpartum period as they adapt to the demands of lactation. Furthermore, differing dynamics of SCH in the days following parturition are associated with varied health and production outcomes, with cows experiencing transient SCH producing more milk and facing fewer negative health events than cows with delayed or persistent SCH. Our objectives were to describe differences in mediators of calcium (Ca) homeostasis between cows experiencing differing Ca dynamics postpartum. A prospective cohort of 89 multiparous Holstein cows from 2 herds in New York were classified into 1 of 4 SCH groups based on mean serum total Ca (tCa) at 1 and 4 d in milk (DIM): normocalcemic (NC; [tCa] >1.89 mmol/L at 1 DIM and >2.25 mmol/L at 4 DIM, n = 30); transient SCH (tSCH; [tCa] ≤1.89 mmol/L at 1 DIM and >2.25 mmol/L at 4 DIM, n = 12); delayed SCH (dSCH; [tCa] >1.89 mmol/L at 1 DIM and ≤2.25 mmol/L at 4 DIM, n = 23); and persistent SCH (pSCH; [tCa] ≤1.89 mmol at 1 DIM and ≤2.25 mmol/L at 4 DIM, n = 24). Blood samples were collected at -5, -1, 1 through 5, 7, and 10 DIM and analyzed for tCa, parathyroid hormone (PTH), and serotonin. Repeated measures ANOVA models were used to analyze differences between SCH groups and changes over time for tCa, PTH, and serotonin. During the prepartum period, tCa was greater in the NC, tSCH, and dSCH cows as compared with the pSCH cows and there was marginal evidence for a difference in PTH between SCH groups. Postpartum tCa varied over time between SCH groups. Mean postpartum (95% confidence interval) tCa for respective SCH groups were NC = 2.32 (2.28, 2.35) mmol/L; tSCH = 2.20 (2.14, 2.25) mmol/L; dSCH = 2.17 (2.13, 2.21) mmol/L; and pSCH = 2.03 (1.99, 2.07) mmol/L. Mean concentrations of PTH in the postpartum period were NC = 70.1 (66.2, 74.4) pmol/L; tSCH = 72.1 (66.1, 79.2); dSCH = 75.8 (70.8, 81.5) pmol/L; and pSCH = 77.7 (72.4, 83.9) pmol/L. Serotonin was similar between SCH groups pre- and postpartum and followed a cyclical pattern from 1 to 10 DIM. Our results agreed with our hypothesis that differences in postpartum PTH might exist between cows experiencing different dynamics of SCH in the early lactation period; however, further studies are needed to confirm this difference. If true, this would suggest that Ca homeostasis may be disrupted in cows with dSCH and pSCH. Gaining a better understanding of these modulatory differences may aid in the prevention, management, and treatment of SCH.

Evaluation of the relationship between ionized and total calcium concentrations in blood during the first week of lactation in dairy cows

BACKGROUND

Diagnosis of subclinical hypocalcemia in cattle is based on concentration of total Ca ([TCa]) in serum or plasma below the reference range, with [TCa] serving as proxy for the concentration of ionized Ca ([iCa]).

HYPOTHESIS/OBJECTIVES

To investigate the relation between [iCa] and [TCa] in periparturient cows over time, and its association with various metabolites.

ANIMALS

Thirty periparturient dairy cows.

METHODS

Prospective observational study. Blood from periparturient cows was obtained between 4 days before and 7 days after calving. Samples underwent blood gas analysis and blood biochemical analysis. The ratio of [iCa] : [TCa] was computed. Repeated measures linear regression analyses, spearman correlation-, Deming regression- and receiver operating characteristic (ROC) analyses were conducted.

RESULTS

Correlations between [iCa] and [TCa] ranged from r = 0.55 to r = 0.84. The diagnostic value of [TCa] to identify cows with [iCa] below the arbitrary cut-off of 1.1 mmol/L was weak in particular during the first 24 hours of lactation, but continuously improved toward the end of the study with areas under the ROC curve increasing from 0.64 at d 0 to 0.93 at d +4 after calving. Strongest association with [iCa] : [TCa] were found for albumin (r2  = 0.58, P < .0001), pCO2 (r2  = 0.45, P = .0003), the standard [HCO3 ] (r2  = 0.22, P = .01), lactate (r2  = 0.16, P = .04) and [NEFA] (r2  = 0.15, P = .05).

CONCLUSION AND CLINICAL IMPORTANCE

The [TCa] is of limited value to identify cows with subnormal [iCa] in the first hours and days of lactation, a finding apparently attributable to the increased variation of a number of metabolic variables that affect the ratio of [iCa] : [TCa].

Noninvasive measurement of blood calcium concentration using electrocardiography in peripartum Jersey cows

We previously developed a noninvasive method for measuring blood calcium concentration (Ca) in Holstein cows on site using electrocardiographic (ECG) variables and calving number, based on a high positive correlation between Ca. Jersey cows easily develop peripartum hypocalcemia compared with other dairy cows. The early detection and treatment of hypocalcemia are particularly important for Jersey cows because delayed treatment can result in various complications. In this study, to establish a simple, noninvasive, on-site diagnosis of hypocalcemia in perinatal Jersey cows, we attempted to create an equation for estimating Ca using ECG waveforms. Overall, 112 Jersey cows 0-2 days postpartum were used. The ECG findings of these cows were measured using the base-apex lead for 30 s and the corrected ST interval (STc = ST peak interval/SS peak interval0.5) was calculated. Simultaneously, blood was collected from the tail vein, and the serum total Ca (tCa) and serum ionized Ca (iCa) were measured. Several items considered related to Ca were investigated. A strong positive correlation was observed between the tCa and iCa (r = 0.96). A positive correlation was observed between the tCa and STc-1 (r = 0.83). Furthermore, significant correlations were observed between skin temperature, calving number, vigor level, rumen movement, and auricle temperature (p < 0.05). Of these, multiple regression analysis was performed to calculate the tCa estimation formula with the STc and calving number (categorized into primipara, second parity, and third or more parity) as explanatory variables and the tCa as the objective variable (r = 0.85, p < 0.01). Of 15 postpartum Jersey cows, the estimation formula could mostly distinguish between cows with hypocalcemia, those with subclinical hypocalcemia, and normal cows. Blood Ca in peripartum Jersey cows can be noninvasively estimated using ECG variables and calving number.

Calcium dynamics and associated temporal patterns of milk constituents in early-lactation multiparous Holsteins

At the onset of lactation, calcium (Ca) homeostasis is challenged. For the transitioning dairy cow, inadequate responses to this challenge may result in subclinical hypocalcemia at some point in the postpartum period. It has been proposed that dynamics of blood Ca and the timing of subclinical hypocalcemia allow cows to be classified into 4 Ca dynamic groups by assessing serum total Ca concentrations (tCa) at 1 and 4 days in milk (DIM). These differing dynamics are associated with different risks of adverse health events and suboptimal production. Our prospective cohort study aimed to characterize the temporal patterns of milk constituents in cows with differing Ca dynamics to investigate the potential of Fourier-transform infrared spectroscopic (FTIR) analysis of milk as a diagnostic tool for identifying cows with unfavorable Ca dynamics. We sampled the blood of 343 multiparous Holsteins on a single dairy in Cayuga County, New York, at 1 and 4 DIM and classified these cows into Ca dynamic groups using threshold concentrations of tCa (1 DIM: tCa <1.98 mmol/L; 4 DIM: tCa <2.22 mmol/L) derived from receiver operating characteristic curve analysis based on epidemiologically relevant health and production outcomes. We also collected proportional milk samples from each of these cows from 3 to 10 DIM for FTIR analysis of milk constituents. Through this analysis we estimated the milk constituent levels of anhydrous lactose (g/100 g of milk and g/milking), true protein (g/100 g of milk and g/milking), fat (g/100 g of milk and g/milking), milk urea nitrogen (mg/100 g of milk), fatty acid (FA) groups including de novo, mixed origin, and preformed FA measured in grams/100 g of milk, by relative percentage, and grams/milking, as well as energy-related metabolites including ketone bodies and milk-predicted blood nonesterified FA. Individual milk constituents were compared among groups at each time point and over the entire sample period using linear regression models. Overall, we found differences among the constituent profiles of Ca dynamic groups at approximately every time point and over the entire sample period. The 2 at-risk groups of cows did not differ from each other at more than one time point for any constituent, however prominent differences existed between the milk of normocalcemic cows and the milk of the other Ca dynamic groups with respect to FA. Over the entire sample period, lactose and protein yield (g/milking) were lower in the milk of at-risk cows than in the milk of the other Ca dynamic groups. In addition, milk yield per milking followed patterns consistent with previous Ca dynamic group research. Though our use of a single farm does limit the general applicability of these findings, our conclusions provide evidence that FTIR may be a useful method for discriminating between cows with different Ca dynamics at time points that may be relevant in the optimization of management or development of clinical intervention strategies.

The Association between Prepartum Rumination Time, Activity and Dry Matter Intake and Subclinical Hypocalcemia and Hypomagnesemia in the First 3 Days Postpartum in Holstein Dairy Cows

Changes in prepartum behaviors such as total daily rumination (TDR), total daily activity (TDA) and dry matter intake (DMI) have the potential to be used as early indicators for cows at risk for subclinical hypocalcemia (SCH) or hypomagnesemia (HYM) after calving. Our objective was to investigate associations between average daily rate of change in total daily rumination (ΔTDR), total daily activity (ΔTDA) and dry matter intake (ΔDMI) from -3 days prepartum to calving with SCH and HYM at D0 or D3 relative to calving. Prepartum TDR, TDA and DMI were measured in 64 Holstein dairy cows. Blood samples were taken at D0 and D3 post-calving for the measurement of total plasma Ca and Mg concentration. Linear regression models were used to analyze the association between ΔTDR, ΔTDA and ΔDMI and SCH and HYM at D0 and D3 relative to calving. Potential confounding variables were offered to the models and backwards selection was used to determine which covariates to retain. No significant differences in prepartum ΔTDR, ΔTDA or ΔDMI were found between cows with or without SCH and HYM at D0 and D3. Our results suggest that the change in TDR, TDA and DMI in the last 3 days prepartum are not effective predictors for cows that will have SCH or HYM in the first 3 days postpartum.

Considerations in the Diagnosis and Treatment of Early Lactation Calcium Disturbances

This article reviews the history of clinical hypocalcemia and the evolving definition of subclinical hypocalcemia, targeting a concept for consideration that not all hypocalcemia is negative. With a goal of presenting bovine practitioners information to assist with individual animal hypocalcemia diagnosis and treatment as well as herd-level monitoring and prevention, we present current methods of direct calcium measurement, therapeutic interventions for clinical hypocalcemia, and postpartum calcium supplementation options and their efficacy. We encourage veterinarians to understand calcium dynamics in the immediate postpartum period and evaluate how individual cow therapy and herd prevention protocols can assist with supporting calcium regulation.

The association of subclinical hypocalcemia at 4 days in milk with reproductive outcomes in multiparous Holstein cows

Delayed or persistent episodes of subclinical hypocalcemia (SCH) have been associated with reduced milk production and feed intake and they put cows at risk for additional disease development. However, little is known about the effect of delayed or persistent SCH on reproductive outcomes. The objectives of our study were to describe the association between SCH status at 4 d in milk (DIM) with the odds of pregnancy to first service and time to pregnancy through 150 DIM. Data were collected from multiparous Holstein cows (n = 697) from 4 farms in New York State that did not receive supplemental Ca during the first 5 DIM. Cows were classified into 1 of 2 SCH groups based on blood total Ca (tCa) at 4 DIM: normocalcemic (NC; n = 515) if tCa >2.2 mmol/L at 4 DIM or SCH (n = 182) if tCa ≤2.2 mmol/L at 4 DIM. We created a multivariable logistic regression model to assess the association between SCH group and pregnancy to first service and a time-to-event analysis to evaluate the effect of SCH group on the hazard of pregnancy by 150 DIM. Cows that were SCH at 4 DIM had lower odds of pregnancy to first service [odds ratio = 0.75, 95% confidence interval (CI) = 0.61 to 0.93, incidence = 18.1%] compared with their NC counterparts (incidence = 27.4%). Similarly, SCH cows tended to have a lower hazard of pregnancy by 150 DIM (hazard ratio = 0.82, 95% CI = 0.67 to 1.01, incidence = 65.4%) than NC cows (incidence = 70.7%). Our results indicate that delayed or prolonged reductions in blood Ca in the early postpartum period, resulting in SCH at 4 DIM, were associated with reduced reproductive outcomes in multiparous cows. Our findings, in conjunction with previous reports of the negative associations of delayed or persistent SCH on health and production, suggest that reductions in blood Ca beyond the first day of lactation might be indicative of maladaptation to lactation, and the ramifications can persist beyond the immediate postpartum period.

Effects of feeding rumen-protected methionine pre- and postpartum in multiparous Holstein cows: Health disorders and interactions with production and reproduction

Study objectives were to evaluate the effects of feeding rumen-protected Met (RPM) in pre- and postpartum total mixed rations (TMR) on health disorders and the interactions of health disorders with lactation and reproductive performance. Multiparous Holstein cows [470; 235 cows at University of Wisconsin (UW) and 235 cows at Cornell University (CU)] were enrolled at approximately 4 wk before parturition and housed in close-up dry cow (n = 6) and replicated lactation pens (n = 16). Pens were randomly assigned to treatment diets (pre- and postpartum, respectively): (1) control (CON): basal diet = 2.30% and 2.09% Met as % of metabolizable protein (MP) (UW) or 2.22% and 2.19% Met as % of MP (CU); (2) RPM: basal diet fed with RPM with 2.83% and 2.58% Met (Smartamine M, Adisseo Inc.; 12 g prepartum and 27 g postpartum), as % of MP (UW) or 2.85% and 2.65% Met (Smartamine M; 13 g prepartum and 28 g postpartum), as % of MP (CU). Total serum Ca was evaluated at the time of parturition and on d 3 ± 1 postpartum. Daily rumination was monitored from 7 d before parturition until 28 d postpartum. Health disorders were recorded during the experimental period until the time of first pregnancy diagnosis (32 d after timed artificial insemination; 112 ± 3 d in milk). Uterine health was evaluated on d 35 ± 3 postpartum. Time to pregnancy and herd exit were evaluated up to 350 d in milk. Treatment had no effect on the incidence of most health disorders and did not alter daily rumination. Cows fed RPM had reduced subclinical hypocalcemia (13.6 vs. 22%; UW only) on day of parturition relative to CON. Percentage of cows culled (13.1 vs. 19.3%) and hazard of herd exit due to culling [hazard ratio = 0.65, 95% confidence interval (CI): 0.42-1.02] tended to be reduced for cows fed RPM compared with CON. Moreover, cows fed RPM had greater milk protein concentration and protein yield overall, although retrospective analysis indicated that RPM only significantly increased protein yield in the group of cows with one or more health disorders (1.47 vs. 1.40 kg/d), not in cows without health disorders (1.49 vs. 1.46 kg/d) compared with CON. Overall, treatment had no effect on pregnancy per timed artificial insemination; however, among cows with health disorders, those fed RPM had reduced time to pregnancy compared with CON (hazard ratio = 0.71, 95% CI: 0.53-0.96). Thus, except for subclinical hypocalcemia on the day of parturition, feeding RPM in pre- and postpartum TMR did not reduce the incidence of health disorders, but our retrospective analysis indicated that it lessened the negative effects of health disorders on milk protein production and time to pregnancy.

Validation of a blood gas device for ionized calcium analysis in Holstein cows

BACKGROUND

Accurate analysis of ionized calcium (iCa) is critical for the detection of hypocalcemia or subclinical hypocalcemia. The Edan i15 Vet (EDAN) blood gas device has not been validated for iCa in dairy cows.

OBJECTIVES

We aimed to validate the EDAN blood gas device against the Gem Premier 3000 (GEM) analyzer by measuring iCa concentrations and evaluating the ability of these measurements, compared with serum total calcium (TCa) concentrations, to diagnose subclinical hypocalcemia.

METHODS

iCa concentrations were measured with the EDAN and GEM devices, and serum TCa concentrations were measured with a wet biochemistry method with blood from 125 lactating Holstein cows between calving to day 27 postpartum.

RESULTS

Bland-Altman plots showed a mean and total bias of 0.05 and 0.24 mmol/L for the EDAN device, respectively. The intercept did not include zero, but the slope included 1.0 in the Passing-Bablok regression. The sensitivity and specificity (Se/Sp) of the EDAN device were 93/94%, 93/90%, 91/93%, and 85/95% for iCa cut-off values of <1.00, 1.05, 1.10, and 1.15 mmol/L, respectively, as determined with the GEM device. The Se/Sp were 57/82% and 72/80% for EDAN and 57/80% and 72/79% for GEM at serum TCa cut-off points <2.15 and <2.00 mmol/L, respectively. The average iCa concentrations analyzed with the GEM and EDAN devices were 1.04 ± 0.18 and 1.09 ± 0.17, respectively.

CONCLUSIONS

The EDAN device did not have satisfactory agreement with GEM and could not be used interchangeably, but it had satisfactory Se/Sp to diagnose subclinical hypocalcemia compared with the GEM-derived iCa cut-off points. Serum TCa concentration cut-off values were not suitable for diagnosing subclinical hypocalcemia because of unsatisfactory Se/Sp compared with iCa concentrations analyzed by the GEM and EDAN devices. The iCa values analyzed using the EDAN and GEM devices were consistent with previously reported data.

Effect of source and amount of vitamin D on serum concentrations and retention of calcium, magnesium, and phosphorus in dairy cows

The objectives of the experiment were to determine the effects of supplementing 2 amounts of 25-hydroxyvitamin D₃ (calcidiol; CAL) compared with equal amounts of vitamin D₃ (cholecalciferol; CHOL) on serum concentrations, absorptions, and retentions of Ca, Mg, and P in periparturient dairy cows. One hundred seventy-seven (133 parous and 44 nulliparous) pregnant Holstein cows were enrolled in the experiment. Cows were blocked by parity and previous lactation milk yield (parous) or genetic merit for energy-corrected milk yield (nulliparous) and assigned randomly to receive 1 or 3 mg/d of CAL or CHOL in a 2 × 2 factorial arrangement of treatments. Treatments were provided to individual cows as a top-dress to the prepartum diet from 250 d gestation until parturition. The prepartum diet had a dietary cation-anion difference of -128 mEq/kg of dry matter. All cows were fed a common postpartum diet containing 46 μg of vitamin D₃/kg of dry matter without further supplementation of treatments. Concentrations of vitamin D metabolites, Ca, Mg, and P in serum were measured pre- and postpartum, in addition to total-tract digestibility and urinary excretion of Ca, Mg, and P in the prepartum period. Feeding 3 mg compared with 1 mg of CAL increased serum 25-hydroxyvitamin D₃ (CAL1 = 94 vs. CAL3 = 173 ± 3 ng/mL). In comparison, the increment in serum 25-hydroxyvitamin D₃ from feeding 3 mg compared with 1 mg of CHOL was small (CHOL1 = 58 vs. CHOL3 = 64 ± 3 ng/mL). Feeding CAL increased prepartum concentration of P in serum compared with CHOL (CHOL = 1.87 vs. CAL = 2.01 ± 0.02 mM), regardless of the amount fed, but neither source nor amount affected prepartum Ca or Mg in serum. Feeding CAL increased serum Ca and P for the first 11 d postpartum compared with CHOL (CHOL = 2.12 vs. CAL = 2.16 ± 0.01 mM serum Ca; CHOL = 1.70 vs. CAL = 1.78 ± 0.02 mM serum P) but the amount of vitamin D did not affect postpartum concentrations of Ca, Mg, and P in serum. Feeding CAL increased prepartum apparent digestibility of Ca compared with CHOL (CHOL = 26.6 vs. CAL = 33.5 ± 2.8%) but treatments did not affect Ca retention prepartum. Neither source nor amount of vitamin D affected Mg and P apparent digestibility, but CAL decreased the concentration of P excreted in urine during the prepartum period (CHOL = 1.8 vs. CAL = 0.8 ± 0.3 g/d). Calcidiol tended to increase the amount of Ca secreted in colostrum (CHOL = 9.1 vs. CAL = 11.2 ± 0.9 g/d) and Ca excreted in urine postpartum (CHOL = 0.4 vs. CAL = 0.6 ± 0.1 g/d) compared with CHOL. Collectively, feeding CAL at 1 or 3 mg/d compared with CHOL in the last 24 d of gestation is an effective way to increase periparturient serum P concentration and postpartum serum Ca of dairy cows fed a prepartum diet with negative DCAD.

Assessment of Noninferiority of Delayed Oral Calcium Supplementation on Blood Calcium and Magnesium Concentrations and Rumination Behavior in Dairy Cows

We investigated whether delaying oral calcium (Ca) bolus administration to the second day postpartum (DEL) was noninferior to bolus administration within 24 h of calving (CON) in its effects on plasma Ca concentrations during the first five days in milk (DIM). We also investigated the effects of DEL vs. CON strategies on magnesium (Mg) concentrations and daily rumination time (RT). Twenty-three multiparous (parity ≥ 3) dairy cows were randomly assigned to the CON (n = 11) or DEL (n = 12) treatment. Blood Ca and Mg were measured at 1–5 DIM and RT was monitored from −7 d to 7 d relative to calving. The noninferiority margin was a difference in Ca concentration of 0.15 mmol/L. Blood Ca and Mg concentrations and RT were analyzed by multivariable linear mixed models accounting for repeated measures. Blood Ca concentrations were 0.07 mmol/L (95% confidence interval: −0.30–0.17) less in DEL cows than CON cows, thus non-inferiority results were inconclusive. The Ca concentration increased across the first 5 DIM but did not differ between treatments while Mg concentrations decreased in both treatments (p < 0.001). There was no treatment difference in RT (CON: 436 ± 21, DEL: 485 ± 19 min/d). While noninferiority results were inconclusive, similar blood Ca dynamics between CON and DEL treatment strategies indicates that delayed Ca administration is a potential management option for commercial dairy farms; however, additional studies using large sample sizes are warranted to confirm these findings.

Ursache, Verbreitung und evidenzbasierte Therapie sowie Prävention der peripartalen Hypokalzämie

Die peripartale Hypokalzämie ist eine weit verbreitete Stoffwechselstörung, dessen klinische Form etwa 7 % der Milchkühe und dessen subklinische Form fast jede 2. multipare Kuh betrifft. Obwohl sich hinsichtlich Diagnostik und Therapie in den letzten 30 Jahren kaum etwas verändert hat, herrscht bei Landwirten und Tierärzten Unklarheit über die Prävalenz und den Risikozeitraum dieser Stoffwechselstörung. Darüber hinaus gibt es sehr unterschiedliche Angaben darüber, wieviel Kalzium einer Kuh mit klinischer Hypokalzämie substituiert werden sollte. Ziel dieses Übersichtsartikels ist es, die Entstehung und Verbreitung von Hypokalzämie evidenzbasiert darzustellen. Des Weiteren werden die Ergebnisse älterer und neuer Studien zusammengefast, mit dem Ziel eine möglichst genaue Empfehlung zur Behandlung von klinischer Hypokalzämie zu geben. Da in einer 2017 durchgeführten Studie gezeigt wurde, dass der überwiegende Teil deutscher Milchviehbetriebe keine Prophylaxe gegen Hypokalzämie betreibt, werden in dem letzten Teil dieser Arbeit die verschiedenen Prophylaxekonzepte, unter Berücksichtigung der aktuellen Literatur, dargestellt.

Major Nutritional Metabolic Alterations Influencing the Reproductive System of Postpartum Dairy Cows

Early successful conception of postpartum dairy cows is crucial in determining the optimum reproductive efficiency and profitability in modern dairy farming. Due to the inherent high production potential of modern dairy cows, the extra stress burden of peri-parturient events, and associated endocrine and metabolic changes causes negative energy balance (NEBAL) in postpartum cows. The occurrence of NEBAL is associated with excessive fat mobilization in the form of non-esterified fatty acids (NEFAs). The phenomenon of NEFA mobilization furthers with occurrence of ketosis and fatty liver in postpartum dairy cows. High NEFAs and ketones are negatively associated with health and reproductive processes. An additional burden of hypocalcemia, ruminal acidosis, and high protein metabolism in postpartum cows presents further consequences for health and reproductive performance of postpartum dairy cows. This review intends to comprehend these major nutritional metabolic alterations, their mechanisms of influence on the reproduction process, and relevant mitigation strategies.

Potential of a rumen bolus containing 1,25-dihydroxyvitamin D3 glycosides for the prevention of hypocalcaemia in primiparous and multiparous dairy cows

Periparturient hypocalcaemia is a widespread metabolic disorder in dairy cows. Clinical and subclinical cases occur primarily in multiparous (Multi) cows, but subclinical cases have also been reported in primiparous (Primi) cows. A preventive strategy was investigated by administering the physiologically active vitamin D₃ metabolite, 1,25-dihydroxyvitamin D₃ (1,25-dihydroxycholecalciferol, 1,25(OH)₂D₃) as a rumen bolus. The bolus contained tablets of 1,25(OH)₂D₃ glycoside extract from Solanum glaucophyllum (SGE), releasing SGE over several days. The aim was to study the effect of a bolus containing 0 (C) or 500 µg (SGE) of 1,25(OH)₂D₃ on 1,25(OH)₂D₃ and mineral status in periparturient cows up to three weeks into lactation and on colostrum, milk and calves' blood mineral contents. The bolus was administered three to four days prior to expected calving to Primi and Multi cows fed a herbage-based diet (dietary cation-anion difference of +522 mEq/kg DM). One C or SGE bolus was applied to 12 Primi and 12 Multi cows. Blood was regularly sampled (and selected a posteriori for antepartum samples) in regard to the actual calving day (d0), immediately prior to bolus application and at day -2, 0.5, 1, 1.5, 2, 4, 8, 11, 15, 18 and 22. Additional samples included urine (at bolus application, d0.5 and d2), colostrum, milk samples (weekly) and calves' blood (d2). Blood serum 1,25(OH)₂D₃ increased between d0.5 and d2 in Primi-SGE, but remained unchanged in Primi-C, as did parathyroid hormone (PTH) and Ca in all Primi. Urinary Ca of Primi-SGE was increased on d2, indicating regulation of Ca excess. Three Multi-C cows with confirmed clinical hypocalcaemia needed treatment and thus were excluded from the dataset and replaced. Blood serum 1,25(OH)₂D₃ and PTH increased while Ca dropped by 40% between d0.5 and d2 in Multi-C, whereas 1,25(OH)₂D₃, Ca and PTH remained unchanged in Multi-SGE. Blood serum carboxyterminal telopeptide of type I collagen was higher in Primi than in Multi and increased with time, except in Primi-C. Mineral contents in colostrum, milk and blood serum of calves were not influenced to a relevant degree. In conclusion, Primi-C did not, in contrast to Multi-C, develop subclinical hypocalcaemia (<2.0 mmol Ca/l). Prevention of hypocalcaemia with one SGE bolus applied three to four days prior to expected calving was successful in maintaining blood Ca within normal range in Multi over the critical first two days and up to the first three weeks of lactation, without any observed detrimental effects on cows or calves.

A Randomized Clinical Trial Evaluating the Effect of an Oral Calcium Bolus Supplementation Strategy in Postpartum Jersey Cows on Mastitis, Culling, Milk Production, and Reproductive Performance

Simple Summary

The time around parturition is a challenging period in the lactation cycle of high-yielding dairy cows as it is characterized by several endocrine, metabolic, and physiological changes. Among those challenges, calcium demands are rapidly increased to support colostrogenesis and lactogenesis during a time of reduced dry matter intake; invariably, some cows may suffer from clinical and subclinical hypocalcemia. Oral calcium supplementation is a common preventative strategy adopted in the postpartum of high-yielding dairy cows to minimize the negative impact of suboptimal blood calcium concentration during this period. Despite a great number of studies evaluating the effects of oral calcium supplementation in postpartum Holstein cows, very limited information is available for the Jersey breed. This study aimed to evaluate the effect of an oral Ca supplementation strategy in the first 24 h after parturition on health and production outcomes in multiparous Jersey cows. Overall, treatment did not improve milk production or reproductive performance compared to control cows. Additionally, treatment had no effect on early lactation culling. A tendency for a minor impact on the odds of mastitis was evident though it depended on the parity of the cows.

Abstract

The objectives of this study were to evaluate the effects of a postpartum oral calcium supplementation strategy in multiparous Jersey cows on (1) the odds of clinical mastitis in the first 60 days in milk (DIM); (2) the odds of culling up to 60 DIM; (3) the risk of pregnancy in the first 150 DIM; (4) milk production in the first 15 weeks of lactation. A randomized clinical trial was performed in a dairy herd located in west Texas, United States. A total of 809 cows were used in the final analyses. Overall, postpartum oral calcium supplementation did not influence milk production, reproductive performance, or culling. Among second parity cows, oral calcium supplementation tended to decrease the odds of clinical mastitis in the first 60 DIM compared to controls; however, no differences were observed for cows in parities three and greater. To date, data evaluating the effect of postpartum oral calcium supplementation in multiparous Jersey cows are limited. In our study, oral calcium supplementation tended to reduce clinical mastitis in second parity cows. No positive benefits based on the reduction of culling, and improvement of milk production and reproductive performance were evident for the herd included in this study.

Randomized clinical trial to evaluate the effects of a prepartum cholecalciferol injection on postpartum serum calcium dynamics and health and performance in early-lactation multiparous dairy cows

The objectives of the present study were (1) to evaluate the effect of prepartum cholecalciferol treatment on serum Ca concentration during the first 10 d after calving and (2) to evaluate the effect of treatment on subsequent health and performance. Multiparous Holstein cows (n = 377) from one dairy farm were fed a negative dietary cation-anion difference diet (-31 mEq/kg of DM) for the last 21 d of gestation. On d 275, the animals were randomly assigned to a control or a treatment group. Cows in the control group were left untreated, and cows in the treatment group received an injection of 12 × 10⁶ IU of cholecalciferol intramuscularly on the day of enrollment. If treated cows did not deliver the calf within 6 d, they were reinjected with 10 × 10⁶ IU of cholecalciferol. Blood samples were drawn on 1, 2, 3, 5, 7, and 10 days in milk (DIM) and analyzed for serum Ca, P, and Mg concentrations. In a subsample of cows (50 control cows, 35 cows treated once with cholecalciferol, and 15 cows treated twice) serum haptoglobin, nonesterified fatty acids, β-hydroxybutyrate, and 25-hydroxycholecalciferol concentrations were analyzed on 1, 5, and 10 DIM. Binary data [retained placenta (RP), metritis] were analyzed using logistic regression models. Repeated measures ANOVA with first-order autoregressive covariance was performed to evaluate the treatment effect on milk yield over the first 10 test days after parturition, 25-hydroxycholecalciferol, serum Ca, P, Mg, β-hydroxybutyrate, nonesterified fatty acids, and haptoglobin concentrations. Cox proportional hazards were used to model the time to event outcomes (time to pregnancy within 200 d, culling until 300 DIM). After enrollment of 31.4% of cows and a preliminary analysis, adverse reactions became apparent, and the study was stopped. Cows treated with cholecalciferol had a greater risk of incurring RP and metritis. The adjusted mean incidences were 2.0%, 7.7%, and 4.0% for RP, and 21.6%, 39.3%, and 33.3% for metritis for control cows, cows treated once, and cows treated twice with cholecalciferol, respectively. Compared with control cows, cows injected once with 12 × 10⁶ IU of cholecalciferol produced less energy-corrected milk on the first (-3.76 kg) and second (-2.75 kg) test days, respectively. Cows injected twice with cholecalciferol (12 × 10⁶ IU of cholecalciferol and 10 × 10⁶ IU 1 wk later) had a reduced milk yield only at first test day (-3.80 kg). Treatment with cholecalciferol led to a significant increase in 25-hydroxycholecalciferol on d 1, 5, and 10 after calving. Serum Ca and P concentrations were significantly increased in cows treated with cholecalciferol, but serum Mg concentrations were significantly reduced. Haptoglobin concentrations were significantly increased on 5 DIM in cows injected once with 12 × 10⁶ IU of cholecalciferol. Although we observed no effect of treatment on culling until 300 DIM, time to pregnancy was delayed by 34 d in cows injected once with 12 × 10⁶ IU of cholecalciferol. In the present study, injection with 12 × 10⁶ IU of cholecalciferol had detrimental effects on health and milk production despite the beneficial effects on Ca homeostasis.

Effects of feeding rumen-protected linseed fat to postpartum dairy cows on plasma n-3 polyunsaturated fatty acid concentrations and metabolic and reproductive parameters

High-yielding dairy cows experience a negative energy balance and inflammatory status during the transition period. Fat supplementation increases diet energy density, and plasma n-3 polyunsaturated fatty acids (PUFA) have been proposed to improve immune function. This study tested the hypothesis that dietary supplementation with a rumen-protected and n-3 PUFA-enriched fat could ameliorate both the energetic deficit and immune status of postpartum high-yielding dairy cows, improving overall health and reproductive efficiency. At 11 d in milk (DIM), cows were randomly allocated to groups (1) n-3 PUFA (n = 29), supplemented with encapsulated linseed oil supplying additional up to 64 g/d (mean 25 ± 4 g/d) of α-linolenic acid (ALA), or (2) control (n = 31), supplemented with hydrogenated palm oil without ALA content. Fat supplements of the n-3 PUFA and control groups were available through an automated, off-parlor feeding system, and intake depended on the cow's feeding behavior. Plasma ALA concentrations were higher in n-3 PUFA than control cows, following a linear relation with supplement ingestion, resulting in a lower n-6/n-3 ratio in plasma. Metabolic parameters (body condition score and glucose and β-hydroxybutyric acid blood concentrations) were unaffected, but milk yield improved with increased intake of fat supplements. Plasma total adiponectin concentrations were negatively correlated with ingestion of n-3 PUFA-enriched fat supplement, following a linear relation with intake. Conception rate to first AI increased with higher intake of both fats, but a decrease of calving-to-conception interval occurred only in n-3 PUFA cows. Postpartum ovarian activity and endometrial inflammatory status at 45 DIM were unaffected. In conclusion, this study evinced a positive linear relation between rumen-protected linseed fat intake and plasma n-3 PUFA concentrations, which modulated adiponectin expression and improved reproductive parameters.

Effects of postpartum milking strategy on plasma mineral concentrations and colostrum, transition milk, and milk yield and composition in multiparous dairy cows

The effects of postpartum milking strategy on plasma mineral concentrations, blood β-hydroxybutyrate (BHB) concentration, and colostrum, transition milk, and first monthly test milk yield and composition were evaluated in 90 multiparous Jersey and Jersey × Holstein crossbreed cows from a commercial farm. Before first postpartum milking, cows were randomly assigned to the following milking strategies, implemented during the first 2 d postpartum: twice-a-day milking (M2, standard industry practice, milking every 12 h; n = 22), once-a-day milking (M1, milking every 24 h; n = 24), restricted milking (MR, 3-L milking every 12 h; n = 21), and delayed milking (MD, no milking for the first 24 h, and milking every 12 h afterward; n = 23). Blood samples for total plasma Ca, P, and Mg determination were collected from enrollment every 4 h up to 48 h, and at 3 d in milk. Blood BHB concentration was determined at 3 and 11 d in milk. Colostrum and transition milk yields were recorded, and samples were collected at each study milking for IgG and somatic cell count (SCC) determinations. Information for first monthly test milk yield and composition was obtained from the Dairy Herd Improvement Association. Statistical analyses were conducted using generalized multiple linear and Poisson regressions with Dunnett adjustment and M2 as reference group for mean comparisons. Overall, plasma Ca concentration within 48 h after enrollment was higher for MD (2.17 mmol/L), tended to be higher for MR (2.15 mmol/L), and was similar for M1 (2.09 mmol/L) compared with M2 cows (2.06 mmol/L). No statistically significant differences compared with M2 cows were observed for plasma P and Mg concentrations. Colostrum and transition milk and total Ca harvested within 48 h after enrollment were lower for M1, MR, and MD compared with M2 cows. The MD strategy prevented harvesting colostrum with >50 g of IgG/L. No statistically significant effects were detected on plasma mineral concentrations at 3 DIM, blood BHB concentration, colostrum and transition milk SCC within 48 h after enrollment, or milk yield, energy-corrected milk yield, and SCC at first monthly test. Our results suggest that postpartum plasma Ca concentration may be influenced by postpartum milking strategy, without interfering with future milk yield and udder health. Further studies should evaluate whether the proposed milking strategies in early postpartum affect production, reproduction, or health.

Association of low serum calcium concentration after calving with productive and reproductive performance in multiparous Jersey cows

Consequences of postpartum low blood calcium (Ca) concentration are still under study and literature describing this condition in Jersey cows is scarce. A prospective cohort study was conducted to evaluate the association of low serum Ca concentration shortly after calving with milk and energy-corrected milk yields, somatic cell count linear score, and pregnancy to first service and within 150 d in milk in multiparous Jersey cows from 2 commercial herds. Blood samples for serum Ca determination were collected on average at 3 h 10 min postpartum from 352 multiparous Jersey cows. Productive data up to the 10th monthly test were obtained from the Dairy Herd Improvement Association and reproductive data were obtained from herd records. Multiple linear, log-binomial, and Cox's proportional hazards regressions were used to evaluate the association of low serum Ca concentration with productive and reproductive outcomes. Serum Ca concentration ≤2.18 mmol/L was associated with 1.43 and 1.85 kg/d more milk and energy-corrected milk. However, lower serum Ca concentrations were associated with a 0.28-unit-higher somatic cell count linear score per monthly test (Ca ≤2.00 mmol/L), and decreased pregnancy risk at first service (risk ratio = 0.64; Ca ≤1.94 mmol/L) and hazard of pregnancy within 150 d in milk (hazard ratio = 0.40; Ca ≤1.90 mmol/L). The present study is based on a convenience sample of multiparous Jersey cows from 2 commercial herds; further research including more herds and additional blood Ca determinations is needed to describe postpartum blood Ca dynamics and its association with productive and reproductive outcomes for the Jersey breed.

Transition cow metabolites and physical traits influence days to first postpartum ovulation in dairy cows

Physical activities are associated with the health of transition dairy cows and pregnancy outcomes are positively related to early resumption of postpartum estrous cycles. The objective was to assess key metabolites and patterns of prepartum and postpartum physical activity as they relate to the onset of first postpartum ovulation in lactating dairy cows. Close-up dry Holstein cows (n = 82) and late gestation heifers (n = 78) were enrolled beginning 3 wk before expected calving date (Day 0). Cows were fit with Cow SensOor ear tags to assess transitional changes in eating, resting, rumination, high activity, and ear-surface temperatures. Rectal temperatures were assessed and blood samples were collected on Days 0, 3, 7, and 14 to measure concentrations of glucose, free fatty acids (FFA), β-hydroxybutyrate (BHB), calcium, and haptoglobin. Body condition scores (BCS) and body weights (BW) were measured weekly, and blood samples were collected weekly from Day 21 ± 3 through 70 ± 3 to quantify changes in progesterone to detect luteal function after ovulation. Cows first ovulating before median Day 33 were classified as early (n = 76), whereas those first ovulating after Day 33 were classified as late (n = 84). Early ovulating cows first ovulated earlier (P < 0.001) than the late ovulation cows (24.3 ± 1.2 d [range: 16-32 d] vs. 48.8 ± 1.2 d [range: 33-74 d]), respectively. Mean days to first ovulation excluded seven cows that failed to ovulate before insemination. Compared with late ovulating cows, early ovulating cows had lesser (P < 0.05) concentrations of FFA, BHB, and haptoglobin on Days 0, 3, 7, and 14 in addition to having lesser (P < 0.05) rectal temperatures and ear-surface temperatures. Ear-surface temperatures began to decrease 4 d before parturition and remained less (P < 0.05) after calving than cows that subsequently ovulated late. Early ovulating cows tended (P = 0.07) to spend more time eating, and less (P = 0.02) time resting and being active during the first 3 wk after calving, and lost less (P = 0.03) BW and BCS during the first 9 wk compared with late ovulating cows. Although no differences were detected in yields of milk or energy-corrected milk during the first 9 wk after calving, early compared with late ovulating cows produced more (P < 0.01) milk protein. We concluded that metabolic measures during the first 2 wk after calving, and physical and behavioral traits are associated with the onset of postpartum ovarian activity.

Effects of calcium supplementation, incomplete milking, and vitamin D3 injection on serum total calcium concentration during the first 24 hours after parturition in dairy cows fed an anionic diet during late gestation

OBJECTIVE

To evaluate various strategies for prevention of subclinical hypocalcemia (SH) during the first 24 hours after parturition in dairy cows.

ANIMALS

165 multiparous German Holstein cows from 1 herd.

PROCEDURES

All cows were fed a ration with a moderate dietary cation-anion difference (approx 0 mEq/100 g of dry matter; anionic diet) for the last 2 to 3 weeks of gestation. In the first part of a 2-part study, cows were randomly assigned to 1 of 4 treatment groups (no calcium supplementation [n = 30], oral administration of a calcium bolus alone [34] or in combination with IV administration of 500 mL of a calcium solution [34] or incomplete milking during the first 24 hours after parturition [34]). In part 2, cows in their fifth or greater parity were randomly assigned to receive vitamin D₃ (20,000 U/kg, IM; n = 15) 7 days before the predicted calving date or a control group (18). A calcium bolus was orally administered within 30 minutes after parturition to all cows of part 2. Serum total calcium (Ca_t) concentration was measured immediately after parturition and every 2 hours thereafter for 24 hours and compared among treatment groups. Subclinical hypocalcemia was defined as a Ca_t concentration < 2.00 mmol/L.

RESULTS

In part 1, the mean ± SD Ca_t concentration during the 24 hours after parturition for the IV-treated group (2.28 ± 0.42 mmol/L) was greater than that for the other 3 groups, each of which had a mean Ca_t concentration < 2.00 mmol/L. In part 2, the mean Ca_t concentration for the vitamin D₃-treated cows was greater than that for control cows and remained above 2.00 mmol/L for the duration of the observation period.

CONCLUSIONS AND CLINICAL RELEVANCE

Intramuscular administration of vitamin D₃ or IV administration of a calcium solution in combination with oral administration of a calcium bolus might alleviate SH during the first 24 hours after parturition in dairy cows fed an anionic diet during late gestation.

Effects of feeding rumen-protected methionine pre- and postpartum on reproductive outcomes of multiparous Holstein cows

Our primary objective was to evaluate the effect of feeding rumen-protected Met (RPM) in the pre- and postpartum total mixed ration (TMR) on pregnancy per artificial insemination (AI) and pregnancy loss in multiparous Holstein cows. We also evaluated multiple secondary reproductive physiological outcomes before and after AI, including uterine health, ovarian cyclicity, response to synchronization of ovulation, and markers of embryo development and size. A total of 470 multiparous Holstein cows [235 at the University of Wisconsin (UW) and 235 at Cornell University (CU)] were used for this experiment. Experimental treatment diets were applied at the pen level (2 and 4 close-up pens at CU and UW, respectively, and 12 and 6 postfresh pens at CU and UW, respectively); thus, pen was the experimental unit, and cow was the observational unit. Cows were enrolled and randomly assigned to be fed the experimental treatment diets at approximately 4 wk before parturition until 67 d of gestation [147 d in milk (DIM)] after their first service. Close-up dry cow and replicated lactation pens were randomly assigned to treatment diets: RPM, prepartum = 2.83% (UW) and 2.85% (CU), postpartum = 2.58% (UW) and 2.65% (CU); and control (CON), prepartum = 2.30% (UW) and 2.22% (CU), postpartum = 2.09% (UW) and 2.19% (CU; Met as percentage of metabolizable protein). Vaginal discharge and uterine cytology (percentage of polymorphonuclear leucocytes) were evaluated at 35 ± 3 DIM. Cows received timed AI (TAI) at 80 ± 3 DIM after synchronization of ovulation with the Double-Ovsynch protocol. Ovarian cyclicity status, response to synchronization of ovulation, and luteal function were determined by measuring circulating concentrations of progesterone at 35 and 49 ± 3 DIM, 48 and 24 h before TAI, and 8, 18, 22, 25, and 29 d after TAI. Interferon-stimulated gene expression in white blood cells were compared on 18 d after TAI (CU only) and pregnancy-specific protein B concentrations at 22, 25, 29, 32, and 67 d after TAI. Pregnancy status was determined using pregnancy-specific protein B at 25 and 29 d after TAI, and by transrectal ultrasonography at 32, 39, and 67 d after TAI. Embryo and amniotic vesicle size were determined at 32 and 39 d after TAI. Pregnancy per AI (25 d: 64.7 vs. 64.0%, 32 d: 54.3 vs. 55.1% for CON and RPM, respectively) and pregnancy loss (25 to 67 d: 22.6 vs. 19.2% for CON and RPM, respectively) for synchronized cows did not differ. The proportion of cows with purulent vaginal discharge (CON = 7.7 vs. RPM = 4.6%) and cytological endometritis (CON = 20.8 vs. RPM = 23.6%) did not differ. Cyclicity status, ovarian responses to the synchronization protocol, and synchronization rate also did not differ. In addition, fold change for interferon-stimulated genes, concentrations of pregnancy-specific protein B, and embryo size were not affected by treatments. In conclusion, feeding RPM in the pre- and postpartum TMR at the amounts used in this experiment did not affect uterine health, cyclicity, embryo development, or reproductive efficiency in dairy cows.

A Comparison of Rice Husks and Peanut Shells as Bedding Materials on Dairy Cows' Preferences, Behaviour, and Health

Simple Summary

Good bedding materials can increase the comfort potential of the lying surface and enhance the welfare of cows in intensive dairy farms. The preference, behaviour, hygiene, and health of cows are affected by different bedding surfaces. In the current study, we evaluated the preference, behaviour, cleanliness, and health of cows on three bedding materials, peanut shells (PS), rice husks (RH), and a combination of two-thirds peanut shells, one-third rice husk (PRC). The daily behaviour, serum metabolites, and productivity of dairy cows were all within normal values, and no statistical differences were found between all three bedding materials, although cows showed a preference for rice husk when given access to all three bedding materials at the same time. Finally, the results suggest that bedding comprised of peanut shells and peanut–rice combinations are all suitable for maintaining the health and comfort of dairy cows.

Abstract

The provision and quality of bedding materials affect the behaviour, welfare, and health of dairy cows. The objective of this study was to evaluate the preference, behaviour, cleanliness, and physiological status of cows on three bedding materials, peanut shells, rice husks, and a combination of two-thirds peanut shells, one-third rice husk. In an initial experiment, 15 nonlactating, pregnant Holstein cows had free access to all 3 bedding treatments for 39 d. Cows spent more time lying down on rice husk (337 min/d) than on peanut–rice combination (212 min/d) and peanut shell (196 min/d) (p < 0.05), and lay down most often on rice husk (4.35 bouts/d) than on peanut shell (2.55 bouts/d) (p < 0.05) but did not differ between peanut shells and peanut–rice combinations in terms of lying time and lying bouts. In Experiment 2, 12 nonlactating cows were used to assess the effects of the 3 bedding materials on dairy cow behaviour, cleanliness, serum indicators, and productivity. The total duration of lying down (PS: 699.1 min/d, PRC: 645.6 min/d, RH: 852.5 min/d), the frequency of bouts of lying down (PS: 8.7 bouts/d, PRC: 7.6 bouts/d, RH: 11.1 bouts/d), and the mean duration of lying bouts (PS: 83.5 min/bouts, PRC: 91.8 min/bouts, RH: 81.4 min/bouts) did not differ between treatments. Similarly, no differences in eating or drinking behaviour of dairy cows were observed. In terms of hygiene, cleanliness scores did not differ between the three bedding materials, but udder and flank cleanliness decreased and improved, respectively. In addition, treatments did not affect serum metabolites or productivity of the cows. In summary, daily behaviour, serum metabolites, and productivity of dairy cows were all within the normal range, and no statistical differences occurred between the three bedding materials, although cows showed a preference for rice husk when given access to all three bedding materials at the same time. Finally, the results suggest that bedding comprised of peanut shells and peanut–rice combinations are all suitable for maintaining the health and comfort of dairy cows.

Effect of a calcium-energy supplement drink at calving on lactation performance: Milk yield and composition, odds to reach a next lactation, and calving interval

Supplementation of Ca products to cows after calving is common in calving protocols. This study evaluated the effect of a Ca-energy drink voluntarily consumed on milk yield and composition, odds to reach a next lactation, and calving interval. This prospective randomized study included a blinded placebo and was conducted in 10 commercial dairy farms that included 504 Holstein dairy cows. Cows were blocked within farm by calving sequence and parity (primiparous or multiparous). Within each block of 2 animals, cows were randomly assigned to 1 of 2 treatments: a Ca-energy supplement drink (CAE, n = 255) providing 45 g of Ca and other components (dextrose, lactose, protein, fat, other minerals and vitamins), a placebo (i.e., 100 g of cellulose and 20 g of dextrose; CON, n = 249), both strictly offered to the animals for voluntary consumption. Treatments were offered mixed in 20 L of water within 3 h after calving. Milk data were analyzed using 2 approaches. The first, most classical, evaluated the effect of the treatments on observed milk data, whereas the second approach evaluated the effect on milk residuals (i.e., the difference between observed milk data and a prediction made by a herd test-day model). Eighty-one percent of the CAE cows fully consumed the treatment, whereas only 50% of CON cows did. No differences were detected for observed milk yield, nor for composition in multiparous cows. The only production effect observed on multiparous cows was a treatment by time interaction for milk fat yield, reflecting greater yield for CAE cows between 100 and 150 d in milk only. However, primiparous cows receiving CAE had increased milk (+0.8 kg/d) and component yields (i.e., +40 g/d of protein) compared with CON cows. These effects were more evident when milk and milk components residuals data were analyzed (i.e., +1.5 kg/d for milk yield and +57 g/d of protein). This was achieved with a herd test-day model that allowed milk and milk components data to be adjusted for environmental and genetic factors (i.e., farm effect, time effect, age at calving, parity, stage of lactation, breeding value). The treatment had no effect on the probability of reaching the next lactation (i.e., 72% of CAE cows had a next calving against 69% in CON). Primiparous cows receiving CAE had a longer calving interval compared with CON cows. At 400 d after the application of the treatment, 65% of CAE primiparous cows had a next calving, whereas 81% of CON primiparous cows had calved already. The supplementation of the tested oral Ca-energy solution at calving did not increase the probability to reach a next lactation for neither primiparous or multiparous, but positively influenced milk yield and milk component yields for primiparous.

Association of days in close up, gestation length, and rumination around time of calving with disease and pregnancy outcomes in multiparous dairy cows

The purpose of this study was to evaluate the effect of rumination times and days spent in a close-up group before calving (DCU) on early-lactation health and reproductive outcomes in dairy cows. Data were gathered for 719 cows located in a single herd. Herd management and reproductive records were analyzed for cows receiving treatment in the first 30 d of lactation (days in milk; DIM) for clinical mastitis, reproductive tract disease, ketosis, milk fever, and displaced abomasum. Rumination times for each cow were downloaded daily from the herd's automated collar system used to generate heat and health alerts for each cow beginning at 21 d precalving until 14 d postcalving. During the first 30 DIM, 121 cows (18%) developed at least 1 disease-any combination of ketosis (40 cows, 5.9% of total), mastitis (17 cows, 2.5%), metritis (75 cows, 11%), milk fever (17 cows, 2.5%), or displaced abomasum (28 cows, 4.1%); 305 cows (45%) were pregnant again at 100 DIM, and an additional 139 cows (20%) were pregnant at 150 DIM. Principal component analysis was used to determine the relationship between gestation length and DCU and their association with the odds of developing disease in early lactation. We did not find any significant association between precalving rumination time and disease within the first 30 DIM. Higher rumination time in the week before calving was shown to be strongly linked to a shorter time to subsequent pregnancy, whereas rumination times postcalving were not associated with changes in the time to pregnancy. Principal component analysis showed that a curvilinear combination of gestation length and DCU (principal component 1) was significantly associated with changes in disease incidence in the first 30 DIM. Gestation length and time spent in close up are important management factors in reducing the incidence of disease in early lactation, and rumination times around calving may help predict future reproductive outcomes.

Controlled trial of the effect of negative dietary cation-anion difference prepartum diets on milk production, reproductive performance, and culling of dairy cows

Our objective was to assess the effects of feeding negative dietary cation-anion difference (DCAD) prepartum diets on milk production, reproductive performance, and culling. Cows from 4 commercial farms in Ontario, Canada were enrolled in a pen-level controlled trial from November 2017 to April 2019. Close-up pens (1 per farm) with cows 3 wk before calving were randomly assigned to a negative DCAD (TRT; -108 mEq/kg of dry matter; target urine pH 6.0-6.5) or a control diet (CON; +105 mEq/kg of dry matter with a placebo supplement). Each pen was fed TRT or CON for 3 mo (1 period), and then switched to the other treatment for the next period (4 periods per farm). Data from 15 experimental units (8 pen treatments in TRT and 7 in CON), with a total of 1,086 observational units (cows), were included. The effect of treatment on milk yield at the first 3 milk recording tests of lactation was assessed with linear regression models accounting for repeated measures. The risk of pregnancy at first artificial insemination and culling by 30, 60, and 305 d in milk (DIM) were analyzed with logistic regression models, and effects on time to first AI, pregnancy, and culling were assessed with Cox proportional hazards models. All models included treatment, parity, and their interactions, accounting for pen-level randomization and clustering of animals within farm with random effects, giving 10 degrees of freedom for treatment effects. Multiparous cows fed TRT produced more milk at the first (42.0 vs. 38.8 ± 1.2 kg/d) and second (44.2 vs. 41.7 ± 1.3 kg/d) milk tests. However, multiparous cows fed TRT tended to have 0.2 percentage units less milk fat content at these tests. Although multiparous cows fed TRT tended to have greater energy-corrected milk at the first test (least squares means ± standard error: TRT = 46.1 ± 0.9 vs. CON = 43.8 ± 1 kg/d), there were no differences observed in energy-corrected milk at the second or third tests. In primiparous cows, there was no effect of treatment on milk production. Multiparous cows fed TRT had greater pregnancy to first insemination (TRT = 42 ± 3 vs. CON = 32 ± 4%) and tended to have shorter time to pregnancy [hazard ratio (HR) = 1.20; 95% CI: 0.96-1.49]. In primiparous cows fed TRT, time to pregnancy was increased (HR = 0.76; 95% CI: 0.59-0.99). Culling by 30 DIM tended to be less in TRT (3.3 ± 1.1%) than CON (5.5 ± 1.8%). No effect of treatment on culling by 305 DIM was detected in primiparous cows, but in multiparous cows, the TRT diets decreased the odds of culling (21.3 ± 1.9 vs. 31.7 ± 2.8%) and daily risk of culling to 305 DIM (HR = 0.64; 95% CI: 0.46 to 0.89). Under commercial herd conditions, prepartum negative DCAD diets improved milk production and reproductive performance, and reduced culling risk in multiparous cows. In primiparous cows, TRT diets had no effect on milk yield or culling, but increased the time to pregnancy. Our results suggest that negative DCAD diets should be targeted to multiparous cows.

Controlled trial of the effect of negative dietary cation-anion difference on postpartum health of dairy cows

The objective of this study was to assess the effects of feeding negative dietary cation-anion difference (DCAD) dry cow diets on postpartum health. Cows from 4 commercial dairy farms in Ontario, Canada, were enrolled in a pen-level controlled trial from November 2017 to April 2019. Close-up pens (1 per farm), with cows 3 wk before expected calving, were randomly assigned to a negative DCAD [TRT; -108 mEq/kg of dry matter (DM); target urine pH 6.0-6.5] or a control diet (CON; +105 mEq/kg of DM with a placebo supplement). Each pen was fed TRT or CON for 3 mo (1 period) then switched to the other treatment for the next period, with 4 periods per farm. Urine pH was measured weekly until calving, and body condition score (BCS) was measured at enrollment and at 5 wk postpartum. Data from 15 experimental units [8 TRT and 7 CON, with 1,086 (TRT: n = 681; CON: n = 405) observational units (cows)] that received the assigned diet for >1 wk were included. The incidence of milk fever (MF), retained placenta (RP), metritis, hyperketonemia (blood β-hydroxybutyrate >1.2 mmol/L, measured weekly in wk 1 and 2), clinical mastitis within 30 DIM (MAST), displaced abomasum (DA) within 30 d in milk (DIM), purulent vaginal discharge (PVD, assessed once at wk 5), and number of disease events (≥1 or ≥2) were analyzed with logistic regression models with treatment, parity, BCS, and their interactions, accounting for pen-level randomization and clustering of animals within farm with random effects, giving 10 degrees of freedom to test treatment effects. Multiparous cows fed TRT had greater blood calcium between 1 and 4 DIM than multiparous cows fed CON, and the prevalence of subclinical hypocalcemia (total Ca ≤2.14 mmol/L) was lesser when fed TRT compared with CON (d 1: 73 ± 6% vs. 93 ± 4%; d 2: 65 ± 7% vs. 90 ± 5%), with no differences between treatments detected in primiparous cows. We detected interactions of treatment and BCS at enrollment for MF in multiparous cows and of treatment and parity for ≥2 disease events. Overconditioned (BCS ≥3.75) multiparous cows had reduced incidence of MF when fed TRT (TRT: 2 ± 1%, vs. CON: 13 ± 8%). We detected no treatment effects on RP, metritis, hyperketonemia, or PVD incidence. Cows fed TRT had lesser incidence of DA (1.7 ± 0.7% vs. 3.6 ± 1.6%) and tended to have lesser incidence of MAST compared with CON (1.8% ± 0.6% vs. 4.4 ± 1.4%). No treatment effect was detected on ≥1 disease events (TRT: 38 ± 7%, vs. CON: 42 ± 8%); however, multiparous cows on TRT were less likely to have ≥2 disease events than cows on CON (14 ± 4% vs. 23 ± 6%). Under commercial herd conditions, feeding prepartum diets with negative DCAD improved several measures of postpartum health.

Graduate Student Literature Review: What do we know about the effects of clinical and subclinical hypocalcemia on health and performance of dairy cows?

This narrative literature review summarizes findings regarding the associations of clinical and subclinical hypocalcemia with postpartum health, reproduction, and milk production. To better understand the effects of hypocalcemia, we reviewed clinical and subclinical presentations of the condition and the dynamics of blood Ca concentration in the early postpartum period. We summarize and discuss the associations between hypocalcemia and performance of dairy cows. Up to 50% of dairy cows suffer from at least one disease event in the transition period. The important roles of calcium in muscle contraction and immune function make it a key component of metabolism, inflammation, and defense against infection. Although the effect of clinical hypocalcemia (milk fever) on health and performance is clear, the definition of subclinical hypocalcemia (SCH) and its consequences for health and performance are still ambiguous. Differences in study designs, sampling protocols, Ca concentration thresholds, and sample sizes that may be underpowered for health and reproduction outcomes lead to inconsistent conclusions on the effects of SCH. On current evidence, classification of SCH should be based on at least 2 measurements of blood calcium, using cutpoints supported with relevant data, which may vary depending on the outcome of interest. Arbitrary or poorly supported interpretative thresholds for blood Ca concentrations should be abandoned. Transient SCH appears to be associated with greater milk yield, whereas SCH that is present several days after calving is associated with lesser production and greater disease risk. However, when blood calcium is measured days after calving, primary effects of calcium metabolism may be confounded by feed intake, inflammation, or disease, which might either contribute to or be a consequence of hypocalcemia. Additional research is needed to refine sampling schemes to classify SCH, and to better inform the goals and means of prevention of SCH.

Association of subclinical hypocalcemia dynamics with dry matter intake, milk yield, and blood minerals during the periparturient period

Subclinical hypocalcemia (SCH) affects many high-producing dairy cows in the postpartum period. Recent work has shown that cows experiencing prolonged or delayed SCH are at increased risk for disease and produce less milk than cows experiencing a transient reduction in or normal concentrations of plasma Ca following parturition. Our objective was to determine the association between different postpartum SCH dynamics with pre- and postpartum dry matter intake (DMI), milk yield, and blood mineral concentrations. Data were retrospectively collected from multiparous Holstein cows (n = 78), and cows were classified into 1 of 4 SCH groups based on mean blood total Ca (tCa) concentrations at 1 and 4 d in milk (DIM): normocalcemic (NC; [tCa] >1.95 mmol/L at 1 DIM and >2.2 mmol/L at 4 DIM, n = 28); transient SCH (tSCH; [tCa] ≤1.95 mmol/L at 1 DIM and >2.2 mmol/L at 4 DIM, n = 27); delayed SCH (dSCH; [tCa] >1.95 mmol/L at 1 DIM and ≤2.2 mmol/L at 4 DIM, n = 6); and persistent SCH (pSCH; [tCa] ≤1.95 mmol at 1 DIM and ≤2.2 mmol/L at 4 DIM, n = 17). Linear mixed models were created to analyze the change in pre- and postpartum DMI, milk yield, and blood mineral concentrations over time as well as differences between SCH groups. Prepartum intake was similar between groups, but the NC and tSCH cows consumed more feed than the pSCH or dSCH cows during the first 3 wk of lactation. The tSCH cows produced more milk than the other 3 groups during the first 6 wk of lactation. Postpartum blood tCa and Mg were different between SCH groups and were highest in the NC cows and lowest in the pSCH cows. Our results suggest that the high level of DMI consumed by the NC and tSCH cows in the postpartum period supported an appropriate homeostatic response to the increased Ca demands of lactation, allowing for higher milk yield compared with their counterparts experiencing delayed or prolonged episodes of SCH.

Biochemical Bone Markers During the Transition Period Are Not Influenced by Parenteral Treatment With a High Dose of Cholecalciferol but Can Predict Milk Fever in Dairy Cows

Despite being studied extensively, there are still many knowledge gaps in milk fever prevention and it is still a prevalent disease. Various interventions have been used in its prevention; however, none has proven to be entirely effective. The study aimed to assess the effectiveness of high dose vitamin D₃ parenteral (intramuscularly) administration and the mechanism of its action by studying blood minerals and biochemical bone markers. Further, we assessed the potential of biochemical bone markers, measured in the close-up dry period, as predictors of clinical milk fever after calving. The study was conducted on 56 high yielding, clinically healthy dairy cows, before their 4th or higher lactation. They were divided into three groups based on season (summer and winter) and administration (vitamin D). The winter group was considered as the control group. Cows (n = 13) were parenterally administered a single dose of 10 million IU of vitamin D₃ (DUPHAFRAL® D3) ranging between 10 and 2 days before calving (median = 3 days). Each cow was blood sampled once during four sampling period ranges: ~1 month before calving, 10 to 2 days before calving, 12–48 h after calving and 10–20 days after calving. The samples were analyzed for blood minerals, bone specific alkaline phosphatase (bALP) and C-terminal telopeptide of type I collagen (CTx), alkaline phosphatase, and estradiol. Values were compared between samplings and groups. A receiver operating characteristic (ROC) analysis and logistic regression were used to assess the diagnostic accuracy of biochemical bone markers in predicting milk fever. In this study high dose vitamin D₃ supplementation did not statistically reduced the incidence of milk fever (milk fever incidences were 15.4, 39.1, and 25% in the vitamin D, winter and summer groups, respectively). A significant effect of vitamin D₃ administration on blood minerals or biochemical bone markers was not found at any sampling. We found that the use of biochemical bone markers in the close-up dry period to predict clinical milk fever was applicable only in the winter (housed) group. The area under the curve (AUC) for bALP was 0.804 and 0.846 for CTx using ROC analysis. The bALP curve had the best ratio at the cut-off point 13.85 U/L with 90% sensitivity and 64.3% specificity. While CTx had the ratio of 90% sensitivity and 78.6% specificity at the cut-off point 0.149 ng/mL. Close-up dry dairy cows with CTx ≥0.121 ng/mL had a 3.8 times higher chance of succumbing to milk fever. We were unable to prove that high dose vitamin D₃ parenteral administration is a viable technique for milk fever prevention. Biochemical bone markers are a promising tool for predicting milk fever; however, further studies are needed to confirm their clinical use.

Dissolution Rates of Calcium Boluses and Their Effects on Serum Calcium in Dairy Cattle

Purpose

Calcium supplement boluses vary greatly in content and bioavailability.

Methods

In vivo dissolution and bioavailability studies were conducted to compare commercial calcium supplement boluses with various contents of calcium chloride and calcium carbonate. The products studied included: Bolus 1 (high calcium chloride, no calcium carbonate), Bolus 2 (medium calcium chloride, medium calcium carbonate), and Bolus 3 (low calcium chloride, high calcium carbonate). A bolus was placed in a pre-weighed coarse mesh net for 30, 60, 90, 120, 180, and 240 minutes to measure dissolution rates in the rumen of fistulated animals. To measure calcium uptake, 27 Holstein cows (second and third lactation) were randomly allocated to one of three oral calcium protocols: Treatment 1 (two high calcium chloride boluses at time 0); Treatment 2 (one high calcium chloride bolus at time 0 with a second bolus 12 hours later); or Treatment 3 (two high calcium carbonate boluses at time 0). Treatments were initiated within 12 hours following calving and this was considered time 0.

Results

Bolus 1 was the quickest to dissolve (<90 minutes), followed by Bolus 2 (<240 minutes). The high calcium carbonate bolus (Bolus 3) remained after 240 minutes in vivo with a minimum of 75% of the original bolus weight still intact. Cows with severe hypocalcemia (<1.8 mmol/L) responded with a higher serum calcium increase than cows with milder hypocalcemia (>1.8 mmol/L, <2.12 mmol/L). The high calcium carbonate bolus group (Treatment 3) did not show a rapid increase in serum calcium as compared to the high calcium chloride groups (Treatments 1 and 2). The animals receiving Treatment 1 had a greater and more persistent serum calcium response than animals receiving Treatment 2.

Conclusion

The study outcome suggests that calcium chloride/calcium sulfate boluses are more effective at generating a serum calcium response than boluses containing high amounts of calcium carbonate and that two boluses administered rapidly after calving may be more effective than the traditional treatment of giving 2 boluses 12 hours apart.

Monitoring and Improving the Metabolic Health of Dairy Cows during the Transition Period

Simple Summary

The transition from late gestation to early lactation is a challenging period for dairy cows. A successful transition period depends on metabolic adaptation to the new physiological state in early lactation and proper management in order to support the cow’s requirements. This review paper will discuss various aspects of routine and consistent approaches to collect and analyze herd records, to detect unintended disruptions in performance. In addition, we discuss how to incorporate methods to assess health, production, nutrition, and welfare information to monitor cows during the transition period. Lastly, we discuss management strategies that can be implemented to improve the metabolic health and performance of transition dairy cows.

Abstract

The peripartum period of a dairy cow is characterized by several physiological and behavioral changes in response to a rapid increase in nutrient demands, to support the final stages of fetal growth and the production of colostrum and milk. Traditionally, the transition period is defined as the period 3 weeks before and 3 weeks after parturition. However, several researchers have argued that the transition period begins at the time of dry-off (~60–50 days prior to calving) and extends beyond the first month post-calving in high producing dairy cows. Independent of the definition used, adequate adaptation to the physiological demands of this period is paramount for a successful lactation. Nonetheless, not all cows are successful in transitioning from late gestation to early lactation, leading to approximately one third of dairy cows having at least one clinical disease (metabolic and/or infectious) and more than half of the cows having at least one subclinical case of disease within the first 90 days of lactation. Thus, monitoring dairy cows during this period is essential to detect early disease signs, diagnose clinical and subclinical diseases, and initiate targeted health management to avoid health and production impairment. In this review, we discuss different strategies to monitor dairy cows to detected unintended disruptions in performance and management strategies that can be implemented to improve the metabolic health and performance of dairy cows during the transition period.

Metritis in dairy cows is preceded by alterations in biochemical profile prepartum and at parturition

Metritis in dairy cows is classified as a puerperal disease that affects all layers of the uterine epithelium and occurs during the first 21 days after parturition. The objectives of this study were to identify potential predictive biomarkers of metritis, to monitor the biochemical profile of pre-metritic dairy cows, and to evaluate the reproductive performance of dairy cows with metritis. Fifty-five cows without metritis and fifteen cows that showed clinical signs of metritis were enrolled in this study. Blood samples were collected at -21, -14 and - 7 days before calving and at parturition and assayed for urea, creatinine, aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), total cholesterol, fibrinogen, total calcium, β-hydroxybutyrate (BHB) and non-esterified fatty acids (NEFA) concentrations. Serum fibrinogen on 21, 14 and 7 days prepartum and at parturition was the strongest discriminator between metritic and control cows. Moreover, metritic cows had lower (P < 0.05) concentrations of urea, creatinine, cholesterol and calcium and higher (P < 0.05) serum AST, GGT activities, and serum fibrinogen, BHB and NEFA concentrations when compared to control cows. The number of days to first ovulation, insemination, services per pregnancy and days to pregnancy were greater (P < 0.05) for metritic cows than the control group, and the follicle size was smaller (P < 0.05) for metritic cows than the control group. Our results indicate alterations in the biochemical profile of dairy cows with metritis and the negative impact on the reproductive performance of metritic cows raised in tropical conditions. In addition, this study showed that the serum fibrinogen could be used as screening biomarkers to indicate cows that might have metritis during the postpartum period.

Validation of a point-of-care handheld blood total calcium analyzer in postpartum dairy cows

Our objective was to validate a point-of-care handheld blood total calcium analyzer (Ca meter, CM; TD-5220 Vet Ca²⁺, TaiDoc, New Taipei, Taiwan) to estimate circulating Ca concentrations in postpartum dairy cows. Whole blood was collected from 251 multiparous cows between 1 and 4 d in milk from 2 commercial dairy herds in Ontario, Canada. Blood total calcium concentration (tCa) was analyzed in whole blood, fresh plasma, and thawed plasma, and compared with tCa results from thawed serum analyzed in a diagnostic laboratory (using a Cobas Calcium Gen 2 kit, Roche Diagnostics, Indianapolis, IN) as the reference test (RT). Lin's concordance correlation coefficient (βrho;) and Bland-Altman (B-A) plots were assessed to evaluate the agreement between the RT and CM results in each type of sample. Receiver operating characteristic curve analyses were used to describe the accuracy of each test against the categorized RT results (at a cut-point of ≤2.14 mmol/L). Samples where the meter gave a nonquantitative result ("high" or "low"; thawed plasma: 3/247; fresh plasma: 6/100; and whole blood: 20/98) were not included in the βrho; and B-A analyses. Lin's correlation coefficients demonstrated poor agreement between tests (thawed plasma: βrho; = 0.16; fresh plasma: βrho; = 0.21; and whole blood: βrho; = 0.23). Fresh plasma (using a cut-point of 2.55 mmol/L as measured on the CM) had the greatest diagnostic sensitivity (72%), specificity (86%), and accuracy (77%) for determining subclinical hypocalcemia, but that would still misclassify 23% of samples. In addition to substantial variability, the B-A plots revealed bias with changing concentrations of calcium. Because of low sensitivity on whole blood (58%) or thawed plasma (56%), measurement with the CM is not recommended on these types of samples. This rapid and low-cost meter was not sufficiently accurate to quantify blood Ca concentration, but when used with fresh plasma it might be useful as a screening tool for subclinical hypocalcemia.

Acid-base, electrolyte and oxidative status in dairy cows at different stages of the production cycle

Previous studies in the field of acid-base and oxidative status in cows have mainly focused on the transition period (three weeks before and three weeks after calving). The aim of this study was to determine the differences in the parameters of acid-base and oxidative status and electrolyte balance in cows not only during the transition period, but also at other stages of the production cycle. Holstein-Friesian cows were divided into four numerically equal groups (n = 6): early lactating cows (9?2 days in milk - DIM), peak lactating cows (50?5 DIM), late lactating cows (170?10 DIM) and dry cows (10?1 days before calving). Venous blood samples were taken from the cows to analyze acid-base status, electrolyte concentrations and oxidative stress parameters, and to compare group means. Significantly higher pH was observed in early lactating cows than in late lactating cows. Sodium (Na+) concentration was significantly lower in early lactating and peak lactating cows compared to dry cows, while chloride (Cl-) concentration was also lower in late lactating cows compared to dry cows. Plasma glutathione peroxidase (GSH-Px) activity was higher in early lactating cows compared to peak lactating cows. Thus, the highest blood pH, lowest Na+ and Cl- concentrations and highest serum GSH-Px activity were observed in early lactating cows compared to other groups, indicating the highest metabolic and oxidative stress during this period. In conclusion, it would be useful to consider the inclusion of these parameters in standard health assessment procedures in intensive dairy production.

Hemogasometric and biochemical changes caused by diets with high negative cation-anion balance in dairy cows

Abstract This study aimed to evaluate hemogasometric and metabolic indicators in the first postpartum hours of dairy cows that received different cation-anion diets in the prepartum period. Holstein cows (n=14), multiparous, were divided into two groups: (1) acidogenic diet (DA -27.13 mEq/100 g of DM) (n=7) and (2) neutral diet (DN -3.25 mEq/100 g of DM) (n=7), provided from 30 days before the expected calving. Urine samples were collected every three days from the beginning of supplementation until the day of delivery for pH verification. Blood samples were collected at 0, 6, 12, 24, 36, 48, 60 and 72 h postpartum for hemogasometric and biochemical analyses. The animals that received DA presented lower urinary pH. The serum concentration of total calcium, ionized calcium and the incidence of subclinical hypocalcemia did not differ between groups. Animals that received DA presented reduction in blood levels of total plasma proteins, globulins, bicarbonate and blood pH, in addition to increased activity of paraoxone-1 and reduction in the concentration of haptoglobin from animals of DN. In conclusion, we can infer that, anionic diets can alter blood pH, interfere with protein synthesis, and probably improve antioxidant capacity.

The association of prepartum urine pH, plasma total calcium concentration at calving and postpartum diseases in Holstein dairy cattle

The use of anionic salts to prevent milk fever in dairy cattle has been an effective nutritional strategy; however, the degree of acidification that determines the most acceptable productive responses and well-being of the cow is still a controversial topic. The objective of this study was to assess urine pH in prepartum Holstein cows fed anionic diets and determine its association with plasma total Ca, Mg, P, β-hydroxyl-butyrate (BHB) concentrations at parturition and the occurrence of peripartum disorders. This investigation consisted of 2 studies. Study 1 was conducted on a grazing dairy. Between February and May 2019, 60 prepartum multiparous cows were tested for urine pH and plasma metabolite concentration at parturition. Total Ca, P, Mg and BHB at day 1 in milk (DIM) were assessed and statistically analyzed by ANOVA (models for polynomial regression). Study 2 was conducted on a drylot dairy farm. Between July 2018 and January 2019, 203 cows were evaluated for urine pH and followed-up for 30 DIM to obtain the incidence of dystocia, stillbirths, milk fever, retained fetal membranes, metritis, clinical mastitis and ketosis. Cows were categorized based on their last urine pH as group 1: pH > 7.0 (n = 135); group 2: pH between 6.0 and 7.0 (n = 46) and group 3: pH < 6.0 (n = 22). A logistic regression model for each health event was conducted considering urine pH group as the main effect. Urine sample was collected at 2.71 ± 2.84 days before parturition. In study 1, there was a quadratic effect of urine pH on total Ca. Total Ca concentration was higher between urine pH 6.0 and 7.0, while decreasing below pH 6.0 and above pH 7.0. There was a trend (P = 0.11) for a quadratic effect of urine pH on the concentration of plasma BHB at parturition. β-Hydroxyl-butyrate was lower approximately between urine pH 6.5 and 7.5. In study 2, the odds for a stillborn in cows with urine pH < 6.0 was 2.39 (95% CI = 1.06-5.40) times the odds for a stillborn in cows with urine pH ≥ 7.0. There was no association between urine pH and the other diseases. In conclusion, cows with prepartum urine pH < 6.0 and >7.0 had lower concentration of plasma total Ca and tended to have a higher concentration of BHB. Cows with urine pH < 6.0 had a higher incidence of stillbirths than cows with urine pH > 7.0.

Prevalence and risk factors related to anovular phenotypes in dairy cows

The objective of the current study was to evaluate the relationship of body condition score (BCS) at 35 d in milk (DIM), milk production, diseases, and duration of the dry period with prevalence of anovulation at 49 DIM and then, specifically, with the prevalence of each anovular phenotype. We hypothesized that anovular follicular phenotypes, classified based on maximal size of the anovular follicle, have different etiologies. A total of 942 lactating Holstein cows (357 primiparous and 585 multiparous) from 1 herd had ovaries evaluated by ultrasonography at 35 ± 3 and 49 ± 3 DIM to detect the absence of a corpus luteum (CL), and to measure the diameter of the largest follicle. Cows were classified as cyclic at 49 DIM if a CL was observed in at least 1 of the 2 examinations, or anovular if no CL was observed at either examination. Cows considered anovular were divided into 3 groups based on the largest diameter of the largest follicle as follows: ranging from 8 to 13 mm, 14 to 17 mm, or ≥18 mm. Cows were evaluated for the following diseases: retained placenta, metritis, hyperketonemia, mastitis, lameness, respiratory problem, and digestive problem. At 35 DIM, BCS was determined, and milk yield for individual cows was recorded. A total of 28.5% (268/942) of cows were classified as anovular. Anovular cows had longer dry periods (90 vs. 71 d) and smaller BCS than cyclic cows (2.83 vs. 2.99). Cows with a single disease or multiple diseases had 2 and 3-fold increase in odds of being anovular, respectively. Anovular cows had follicles that ranged from 4 to 50 mm. The prevalence of anovular phenotype, among anovular cows, that had the diameter of the largest follicle ranging from 8 to 13 mm, 14 to 17 mm, and ≥18 mm was 29.9 (79/264), 37.5 (99/264), and 32.6% (86/264), respectively. Anovular cows with follicles of 8 to 13 mm had longer dry periods than those with follicles ≥18 mm (104 vs. 74 d), whereas anovular cows with medium size follicles had intermediate days dry (99 d). Cows with small and medium anovular follicles had smaller BCS and greater prevalence of multiple diseases than cyclic cows. For almost all risk factors, the cows with large anovular follicles (≥18 mm) were similar to cyclic cows and different from cows with smaller anovular follicles (8-13 mm). Thus, longer dry periods, less BCS at 35 DIM, and diseases were risk factors for anovulation. Moreover, the risk factors for the 3 distinct anovular follicle phenotypes differed.

Subclinical hypocalcaemia follows specific time-related and severity patterns in post-partum Holstein cows

Hypocalcaemia is a common metabolic disorder of post-parturient dairy cows; enhancement of our knowledge regarding Ca dynamics would improve cow health and welfare. This study investigated the presence of time- and severity-related subclinical hypocalcaemia (SCHCa) patterns in Holstein cows after calving and their association with diseases during the first week of lactation. A total of 938 cows from nine herds were blood sampled on days 1, 2, 4 and 8 post-partum, and serum Ca concentration was measured with atomic absorption. Subclinical ketosis (serum β-hydroxybutyrate≥1.2 mmol/L) and cases of retained foetal membranes, metritis (MET), mastitis, ketosis and displaced abomasum (DA) were recorded. Using receiver operating characteristic (ROC) analysis, the SCHCa cut-off was identified at serum Ca ≤ 2.09 mmol/L. Hierarchical and two-step cluster analysis classified cows to seven clusters based on test day cow Ca records and overall SCHCa status. Two clusters (NORM and HIGH) included 318 normocalcaemic cows and five clusters (SCH-1 to -5) those that were at least once subclinically hypocalcaemic (n = 620). A second ROC analysis was performed in order to distinguish mild from severe cases of SCHCa in these 620 cows; this cut-off was identified at 1.93 mmol/L. The associated risk of disease with Ca clustership was assessed with generalized linear mixed models. Overall incidence of SCHCa was 66.1%. Clusters SCH-1 and SCH-2 included cows with short-term SCHCa of day 1 and day 2, respectively, while SCH-3 included cows with severe and prolonged SCHCa extending to day 4 and beyond. Clusters SCH-4 and SCH-5 included cows with delayed SCHCa, which culminated on days 4 and 8, respectively. Compared to NORM cows in HIGH had lower risk of MET and no cases of DA. Cows in SCH-3 had higher risk of being diagnosed with retained foetal membranes, DA or any disease during the study period. Cows in SCH-5 had higher risk of being diagnosed with ketosis, subclinical ketosis or any disease. In conclusion, there are multiple normocalcaemic and hypocalcaemic patterns that are differently associated with disease risk.