Associations between subclinical hypocalcemia and postparturient diseases in dairy cows

Effects of 25-Hydroxyvitamin D3 and Oral Calcium Bolus on Lactation Performance, Ca Homeostasis, and Health of Multiparous Dairy Cows

Simple Summary

Subclinical hypocalcemia severely affects the lactation and health of dairy cows. Subclinical hypocalcemia is still a concern with cows after postpartum oral Ca; thus, the single treatment approach gradually has shifted to a multitreatment approach in terms of subclinical hypocalcemia. Supplementing 25-hydroxyvitamin D₃ could solve the problem of insufficient vitamin D₃ synthesis and blocked conversion in transition cows. The present study showed that feeding 25-hydroxyvitamin D₃ combined with oral calcium not only improved serum 25-hydroxyvitamin D₃ status and calcium homeostasis, but also had potential benefits on lactation performance and the health status during the transition period.

Abstract

Little information is available regarding the effect of supplementing 25-hydroxyvitamin D₃ during the transition period combined with a postpartum oral calcium bolus on Ca homeostasis. The objectives of the current study were to evaluate the effects of 25-hydroxyvitamin D₃ combined with postpartum oral calcium bolus on lactation performance, serum minerals and vitamin D₃ metabolites, blood biochemistry, and antioxidant and immune function in multiparous dairy cows. To evaluate the effects of 25-hydroxyvitamin D₃ combined with oral calcium, 48 multiparous Holstein cows were randomly assigned to one of four treatments: (1) supplementing 240 mg/day vitamin D₃ without a postpartum oral Ca bolus (control), (2) supplementing 240 mg/day vitamin D₃ with an oral Ca bolus containing 90 g of Ca immediately post-calving (Ca + VitD), (3) supplementing 6 g/day 25-hydroxyvitamin D₃ without an oral Ca bolus (25D), and (4) supplementing 6 g/day 25-hydroxyvitamin D₃ with an oral Ca bolus containing 90 g of Ca immediately post-calving (Ca + 25D). Lactation performance during the first 21 days was measured. Blood was collected at the initiation of calving and then 1, 2, 7, 14, and 21 days relative to the calving date. The yield of milk (0.05 < p < 0.10), energy-corrected milk (p < 0.05), 3.5% fat-corrected milk (p < 0.05), and milk protein (p < 0.05) were significantly higher in 25-hydroxyvitamin D₃-treated groups within 3 weeks of lactation than in vitamin D₃-treated cows. The iCa (p < 0.05) and tCa (p < 0.05) were higher in both Ca and 25D + Ca cows than in the control and 25D groups within 48 h. The concentrations of serum tCa (p < 0.05), tP (p < 0.05), and 25-hydroxyvitamin D₃ (p < 0.05) in 25D and 25D + Ca cows were higher than those in control and Ca cows within 21 days postpartum. Feeding 25-hydroxyvitamin D₃ also showed a lower concentration of malondialdehyde (p < 0.05), interleukin 6 (p < 0.05), and tumor necrosis factor-alpha (TNF-α) (p < 0.05), as well as a higher concentration of alkaline phosphatase (p < 0.05), total antioxidant capacity (p < 0.05), and immunoglobulin G (p < 0.05) than vitamin D₃. Supplementing Ca bolus also showed lower concentrations of alanine transaminase (p < 0.05) and TNF-α (p < 0.05). In conclusion, supplementing 25-hydroxyvitamin D₃ during the transition period combined with a postpartum oral calcium bolus improved lactation performance, Ca homeostasis, and antioxidant and immune function of medium-production dairy cows within 21 days postpartum.

Elevated serotonin coordinates mammary metabolism in dairy cows

Serotonin plays a diverse role in maternal and mammary metabolism. Recent research in the dairy cow has shown a relationship between serotonin and calcium, with increased serotonin concentrations improving calcium homeostasis in the peri‐partum dairy cow. Therefore, the objective was to elucidate how administration of 5‐hydroxy‐l‐tryptophan (5‐HTP), the immediate precursor to serotonin, altered serotonin and calcium metabolism in lactating dairy cows. Twelve mid‐late lactation multiparous cows were blocked by parity, production and days in milk and allocated to a daily intravenous infusion of (i) 1.5 mg/kg of 5‐HTP (n = 6) or (ii) saline (n = 6) for 3 consecutive days. Milk samples were collected daily. Blood samples were collected before and after each infusion with mammary biopsies and blood samples collected at 48, 56, and 72 h relative to termination of first infusion. Infusion of 5‐HTP increased (p = 0.001) circulating serotonin concentrations and decreased blood calcium via a transient hypocalcemia immediately after each infusion (p = 0.02). Treatment with 5‐HTP increased milk calcium concentrations (p = 0.02) and calcium release‐activated channel protein 1 (ORAI1) mRNA at 56 h and protein at 48 h relative to termination of first infusion (p = 0.008 and p = 0.09, respectively). Fifty‐six hours from termination of the first infusion mRNA of parathyroid hormone‐related protein and mammary serotonin content were increased relative to control (p = 0.03 and p = 0.05, respectively). These findings demonstrate the ability of 5‐HTP infusion to increase circulating serotonin concentrations and alter endocrine and mammary autocrine/paracrine calcium and serotonin metabolism in the lactating dairy cow.

Changes in the Relationship between Ionized and Total Calcium in Clinically Healthy Dairy Cows in the Period around Calving

Simple Summary

Hypocalcemia is a widespread problem in dairy cows in the first days after calving, which increases the risk for secondary diseases. In practice, the measurement of total blood serum or plasma calcium is widely used to diagnose hypocalcemia. The present study demonstrates a high discrepancy between total and ionized calcium specifically around calving, suggesting that only ionized calcium provides an accurate indication of the animal’s calcium status during that period. We developed an optimized model for prediction of ionized calcium from total calcium, non-esterified fatty acids, beta-hydroxybutyric acid, cholesterol, and phosphorous. However, the precision of that model is still unsatisfactory.

Abstract

We aimed to establish a model for prediction of iCa from tCa, using multivariable regressions with diverse blood constituents. Blood was taken from 14 cows at days −2, 0, 2, 4, 7, and 14 relative to parturition. Cows were clinically healthy, and no hypocalcaemia prophylaxis and treatment were applied. Total calcium and further parameters were determined from frozen serum. Ionized calcium, blood gases, and electrolytes were determined from heparin-stabilized blood samples. Linear regression between iCa and tCa was estimated. Precision improved only slightly using a multivariable model. Best precision was achieved when estimating the iCa:tCa ratio from other blood constituents. To identify the reason behind the poorly predictive value of tCa for iCa, the relative changes of iCa and tCa around calving were calibrated to the respective values of day −2 (=100%) for each cow. An increase in the iCa:tCa ratio was observed from 0.43 at day −2 to 0.48 at day 0, followed by a gradual decrease towards 0.43 at day 7. We conclude that routine measurement of iCa should be implemented in the diagnosis of hypocalcaemia. An optimized estimate of iCa from tCa with non-esterified fatty acids (NEFA), beta-hydroxybutyric acid, cholesterol, and phosphorous as co-predictors is still poorly satisfying.

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 blood calcium concentration in the first 3 days after parturition and energy balance metabolites at day 3 in milk with disease and production outcomes in multiparous Jersey cows

Research exploring specific associations of markers of negative energy balance and Ca in postpartum Jersey cows with lactation performance is lacking. Our objectives were to evaluate the associations of total Ca concentration (tCa) measured at 1 through 3 d in milk (DIM) and free fatty acids (FFA), β-hydroxybutyrate (BHB), and glucose measured at 3 DIM with (1) the risk of multiparous Jersey cows being diagnosed with early-lactation diseases and culling, (2) milk production in the first 9 wk of lactation, and (3) the risk of pregnancy in the first 150 DIM. A cohort study was performed in 1 dairy herd in Texas. Multivariable Poisson regression models were built to evaluate the association of the analytes of interest with the risks of early-lactation diseases and culling in the first 60 DIM (i.e., binary outcomes). Linear mixed models were used to evaluate the association of the analytes of interest with milk production within the first 9 wk of lactation, and a Cox proportional hazard model was built to assess the risk of pregnancy within 150 DIM. A total of 380 cows were used in the final analyses. Total Ca measured at 1 through 3 DIM was not associated with the risk of metritis. Cows with increased FFA and BHB had an increased risk of being diagnosed with metritis and clinical mastitis, respectively. Increased concentrations of glucose and FFA and decreased tCa at 3 DIM were associated with an increased risk of culling. Reduced tCa concentrations at 1 DIM (≤1.84 mmol/L) and 2 DIM (≤2.04 mmol/L) were associated with increased milk production across the first 9 wk of lactation compared with tCa concentrations above those thresholds. Total Ca was not associated with milk production when assessed at 3 DIM, whereas increased FFA (≥0.37 mmol/L) and decreased glucose (≤2.96 mmol/L) at 3 DIM were associated with increased milk production. None of the metabolites measured were associated with the risk of pregnancy in the first 150 DIM. Our results demonstrate that tCa concentration assessed in the first 3 DIM show temporary associations with milk production and culling in multiparous Jersey cows. Although increased concentration of FFA assessed at 3 DIM was associated with greater milk yield, it was a detrimental factor for the risk of metritis. This study attempted to better elucidate the relationship of tCa, FFA, BHB, and glucose assessed in early postpartum with health and performance of Jersey cows. Based on this study, assessments performed at 3 DIM using tCa concentration ≤1.99 mmol/L for increased risk of early-lactation culling and FFA ≥0.43 mmol/L for increased risk of metritis could be used as starting points. More studies evaluating the dynamics of energy balance markers and tCa in postpartum Jersey cows using a greater number of herds are needed to better inform dairy consultants on critical levels for exacerbated postpartum negative energy balance and subclinical hypocalcemia for the Jersey breed.

The deleterious effect of postpartum pyometra on the reproductive indices, the metabolic profile, and oxidant/antioxidant parameters of dairy cows

Background and Aim:

Postpartum uterine infectious diseases, such as pyometra, have discrepancy with both health and, subsequently, productivity of dairy cows due to its high prevalence and the high cost of treatment. Therefore, this study investigates the influence of pyometra on the reproductive indices, the metabolic profile, and oxidant/antioxidant parameters of the pyometric animal compared to those of healthy ones.

Materials and Methods:

The study included 30 cows. The animals were differentiated into two groups of 15 cows each: A group of pyometra and a control group. All pyometric cows were subjected to breeding soundness examination after the end of pyometra and were compared to the control group. Blood samples were obtained to assess the levels of glucose, non-esterified fatty acids (NEFA), triglycerides (TGs), cholesterol, albumin, total protein, alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase (ALP), blood urea nitrogen (BUN), creatinine, calcium (Ca), phosphorus, sodium, potassium, progesterone hormone (P4), malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and superoxide dismutase.

Results:

Results revealed significant prolonged duration of first estrus, the days open, and the required number of services due to pyometra. The pyometra group yielded increased levels of NEFA, TGs, ALP, BUN, creatinine, MDA, and progesterone hormone. In addition, significant decrease in the levels of glucose, cholesterol, albumin, Ca, phosphorus, sodium, TAC, GPx, and superoxide dismutase was observed in the pyometra group. Finally, no difference in the concentrations of total protein, ALT, AST, and potassium was observed in the pyometra group.

Conclusion:

The reproductive indices was adversely influenced in cows with postpartum pyometra, and metabolic profile, involving energy balance signals and liver function indicators, revealed differences between the two groups. Increased levels of oxidative stress parameters and decrease levels of antioxidant levels were also found, suggesting that pyometra is an incentive for oxidative stress. Overall, checking the energy balance, metabolic imbalances, and oxidant/antioxidant profile, accompanied with pre-emptive procedures during the postpartum period, is essential and can reduce the chances of such diseases and possible noxious results in highly productive cows.

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.

Factors That Optimize Reproductive Efficiency in Dairy Herds with an Emphasis on Timed Artificial Insemination Programs

Simple Summary

Reproductive efficiency is critical for profitability of dairy operations. The first part of this manuscript discusses the key physiology of dairy cows and how to practically manipulate this reproductive physiology to produce timed artificial insemination (TAI) programs with enhanced fertility. In addition, there are other critical factors that also influence reproductive efficiency of dairy herds such as genetics, management of the transition period, and body condition score changes and improve management and facilities to increase cow comfort and reduce health problems. Using optimized TAI protocols combined with enhancing cow/management factors that impact reproductive efficiency generates dairy herd programs with high reproductive efficiency, while improving health and productivity of the herds.

Abstract

Reproductive efficiency is closely tied to the profitability of dairy herds, and therefore successful dairy operations seek to achieve high 21-day pregnancy rates in order to reduce the calving interval and days in milk of the herd. There are various factors that impact reproductive performance, including the specific reproductive management program, body condition score loss and nutritional management, genetics of the cows, and the cow comfort provided by the facilities and management programs. To achieve high 21-day pregnancy rates, the service rate and pregnancy per artificial insemination (P/AI) should be increased. Currently, there are adjustments in timed artificial insemination (TAI) protocols and use of presynchronization programs that can increase P/AI, even to the point that fertility is higher with some TAI programs as compared with AI after standing estrus. Implementation of a systematic reproductive management program that utilizes efficient TAI programs with optimized management strategies can produce high reproductive indexes combined with healthy cows having high milk production termed “the high fertility cycle”. The scientific results that underlie these concepts are presented in this manuscript along with how these ideas can be practically implemented to improve reproductive efficiency on commercial dairy operations.

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.

Menthol stimulates calcium absorption in the rumen but not in the jejunum of sheep

Stimulation of Ca²⁺ absorption can counteract hypocalcemia at the onset of lactation. The plant bioactive lipid compound (PBLC) menthol is an agonist for nonselective cation channels of the transient receptor potential (TRP) family. It acutely stimulated Ca²⁺ absorption in ruminal epithelia of nonadapted animals ex vivo and caused higher plasma Ca²⁺ concentrations in cows and sheep in vivo. To elucidate the pathway by which menthol feeding increases plasma Ca²⁺ level, the present study aimed to investigate the long-term dose-dependent effects of dietary menthol-rich PBLC on Ca²⁺ absorption and mRNA abundances of TRP channels in both rumen and jejunum. Twenty-four growing Suffolk sheep were equally distributed to a Con, PBLC-L, and PBLC-H group, which received 0, 80, and 160 mg/d of a menthol-rich PBLC. After 4 wk, ruminal and jejunal epithelia were analyzed for mRNA abundances of TRPA1, TRPV3, TRPV5-6, and TRPM6-8 genes. The Ca²⁺ flux rates and electrophysiological properties of epithelia from rumen and mid-jejunum were measured in Ussing chambers in the presence and absence of mucosal Na⁺. Acute changes in Ca²⁺ flux rates were measured after mucosal application of 50 µM menthol. Ruminal epithelia had quantifiable transcripts of TRPV3 = TRPM6 >TRPM7 >TRPA1 with no difference among feeding groups. Jejunum had quantifiable transcripts of TRPM7 >TRPA1 ≥ TRPM6 ≥ TRPV6 >TRPV5, where TRPA1, TRPV5, and TRPV6 tended to decrease linearly with increasing PBLC dose. Absorptive net flux of Ca²⁺ was detected only in the rumen, whereas jejunum showed a high passive permeability to Ca²⁺. Net flux rates of Ca²⁺ in the rumen increased in a quadratic manner (highest in PBLC-L animals) and were systematically decreased with the omission of mucosal Na⁺. Short-circuit current increased in both PBLC feeding groups compared with Con only in the rumen. Acute application of menthol-stimulated mucosal-to-serosal and net Ca²⁺ flux rates only in ruminal epithelia with higher stimulation in PBLC-fed animals. We conclude that Ca²⁺ transport is mainly active and transcellular in the rumen. It most likely involves TRPV3 that can be stimulated by menthol. Pre-feeding of menthol-rich PBLC enhances ruminal Ca²⁺ absorption and sensitizes it to acute stimulation by menthol. By contrast, intestinal Ca²⁺ absorption is not sensitive to menthol stimulation. Menthol could be used as a tool to enhance ruminal Ca²⁺ absorption and to prevent hypocalcemia in dairy cows.

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.

Association between serum calcium dynamics around parturition and common postpartum diseases in dairy cows

The objective of this study was to compare periparturient serum Ca dynamics (CaDyn) in cows with and without diseases in early lactation. The study enrolled 1,949 cows from a commercial dairy farm in northern Germany. Blood samples were drawn 7 d before expected calving date and on d 0, 1, 3, and 7 after calving and analyzed for serum Ca concentration. Cows were monitored for clinical hypocalcemia (CH), ketosis, left displaced abomasum (LDA), retained placenta, acute puerperal metritis (APM), mastitis, and pneumonia. To evaluate the association between CaDyn and diseases during the transition period, repeated measures ANOVA with first-order autoregressive covariance were performed. Serum CaDyn of healthy cows (i.e., without any of the aforementioned diseases) was compared with CaDyn of cows with one of the aforementioned diseases (CH, ketosis, APM, mastitis, LDA, and pneumonia), and cows with multiple diseases (CH+, ketosis+, APM+, mastitis+, LDA+, and pneumonia+). Separate models were built for primiparous and multiparous cows. For primiparous cows, we evaluated the association between CaDyn and ketosis (healthy cows vs. cows with ketosis vs. cows with ketosis+) and CaDyn and APM (healthy cows vs. cows with APM vs. cows with APM+). The same models were built for multiparous cows. Three additional models were built for multiparous cows to evaluate the association between CaDyn and CH (healthy cows vs. cows with CH vs. cows with CH+), mastitis (healthy cows vs. cows with mastitis vs. cows with mastitis+), or LDA (healthy cows vs. cows with LDA vs. cows with LDA+). In primiparous cows, serum Ca concentrations of cows with ketosis, APM, and APM+ were significantly reduced on d 3 and 7 after calving, compared with healthy cows. Serum Ca concentrations of primiparous cows with ketosis+ were reduced on d 3, but not on d 7 after calving. Multiparous cows with CH had significantly reduced serum Ca concentrations on d 0, 1, and 3 compared with healthy cows. On d 3 and 7, serum Ca concentration of CH+ cows was significantly reduced compared with healthy multiparous cows. Multiparous cows with ketosis and ketosis+ had significantly reduced serum Ca concentrations on d 1 and 3 compared with healthy cows. Cows with APM+ had significantly increased serum Ca concentrations on d 0 and reduced serum Ca concentrations on d 3, compared with healthy cows. Whereas multiparous cows with mastitis had a reduced serum Ca concentration on d 1, mastitis+ cows had a reduced serum Ca concentration on d 1 and 3, compared with healthy multiparous cows. Overall, multiparous cows with LDA+ had reduced serum Ca concentrations. Especially a delayed onset of hypocalcemia (d 3 and 7) was indicative for the development of disease in primiparous cows. In multiparous cows, reduced serum Ca concentrations on d 1 and 3 were associated with occurrence of diseases. Future studies should evaluate whether reduced serum Ca concentrations are a cause or concomitant circumstance of diseases in early lactation.

Effects of postpartum oral calcium supplementation on milk yield, milk composition, and reproduction in multiparous Jersey and Jersey × Holstein crossbreed cows

The objective of the present study was to evaluate the effects of postpartum oral calcium supplementation on milk yield, energy-corrected milk yield, milk fat concentration, milk protein concentration, and somatic cell count linear score across the first 3 monthly tests postpartum, peak milk yield, risk of pregnancy at first service, and hazard of pregnancy by 150 d in milk on 1,129 multiparous Jersey and Jersey × Holstein crossbreed cows from 2 commercial dairies. After calving, cows were systematically assigned to control (no oral calcium supplementation; n = 567) or oral calcium supplementation at 0 and 1 d in milk (oral Ca; 50 to 60 g of calcium as boluses; n = 562). Monthly test milk yield, composition, and somatic cell count information was obtained from the Dairy Herd Improvement Association. Herd records were used for reproductive data. Statistical analysis was conducted using generalized multiple linear, Poisson, and Cox's hazard regressions. Treatment effects were evaluated considering cow-level information available at parturition (parity, breed, previous lactation milk yield, previous lactation length, dry period length, gestation length, body condition, and locomotion score at calving, calving ease, and calf sex). In addition, for a subset of cows serum calcium concentration before treatment administration was evaluated (n = 756). Overall, oral calcium supplementation did not affect the evaluated productive and reproductive variables. However, effects conditional to previous lactation length and calving locomotion score were observed. Milk yield and energy-corrected milk yield across the first 3 monthly tests were 1.8 kg/d higher for supplemented cows with a previous lactation length within the fourth quartile, compared with control cows on the same quartile. Energy-corrected milk yield tended to be 1.1 kg/d lower for supplemented cows with a previous lactation length within the first quartile, compared with control counterparts. Peak milk yield tended to be 1.6 kg higher for supplemented cows with a calving locomotion score ≥2, compared with control cows with the same locomotion score. Treatment effects were not conditional to serum calcium concentration before treatment administration. Our results suggest that postpartum oral calcium supplementation effects are conditional to cow-level factors such as previous lactation length and calving locomotion score in multiparous Jersey and Jersey × Holstein crossbreed cows.

Effects of postpartum treatment with oral calcium formate on serum calcium, serum metabolites, and the occurrence of diseases at the beginning of lactation of high-producing dairy cows

This study aimed to evaluate the effects of oral administration of calcium (Ca) formate in the postpartum of high-producing dairy cows on calcemia, on other blood biochemical markers, and on the occurrence of diseases at the beginning of lactation. One hundred and twenty healthy Holstein cows, distributed according to the lactation order (first, second, third and fourth to sixth), were treated or not with oral Ca formate (two doses: one after calving and one 24 h later; equivalent to 50 g of Ca per dose), comprising 8 groups (n = 15). The following variables were measured in the blood serum of samples collected after calving (0 h) and after 24, 48, 72, and 96 h: total Ca, phosphate (P), magnesium (Mg), non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), glucose, total protein (TP), albumin (Alb), urea nitrogen (BUN), aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT). Blood BHB was also measured at 7, 14, and 21 DIM. For the assessment of disease occurrence, cows were distributed in treated (n = 60) and untreated (n = 60) groups and in hypocalcemic (n = 71) and normocalcemic (n = 49) groups. Two-way repeated measures ANOVA and a chi-square test were used for comparisons. The lactation order did not influence the studied blood constituents, except for primiparous cows which had the highest calcemia. Serum Ca was lower up to 24 h and increased after 48 h and subclinical hypocalcemia (SCH) ([Ca] < 2.125 mmol/L) was more frequent in cows with a higher number of lactations. Treatment with Ca formate had no effect on the variation of serum Ca and the other studied variables in the first days of lactation. Treated and untreated cows did not differ in terms of milk yield at 21 DIM, the presentation of diseases at the beginning of lactation, the rate of discard or death up to 60 DIM and the frequency of SCH (60 % and 58 %, respectively). Hypocalcemic cows became more ill (64.8 % vs. 42.9 %; P = 0.028) and had a higher frequency of retained placenta (43 % vs. 20.7 %; P < 0.001). Oral administration of Ca formate after calving and 24 h later is not justified as a preventive measure to be adopted indiscriminately in dairy herds. Studies involving larger number of animals may clarify whether the selective treatment of cows with a higher risk of hypocalcemia is advantageous.

The behavior of dairy cattle in the transition period: Effects of blood calcium status

The aim of this study was to use an automated behavior-monitoring system to objectively assess the association between lying and activity behavior in the precalving, calving, and postcalving periods between multiparous and primiparous cows with (1) normocalcemia, (2) subclinical hypocalcemia, or (3) clinical hypocalcemia at calving. Behavioral data and blood serum samples were collected from 51 multiparous and 21 primiparous Holstein dairy cattle. Blood samples from the coccygeal vein were taken within 24 h of calving, and serum was analyzed to measure total calcium concentration. Cows were classified into one of 3 categories: normocalcemia (serum calcium concentration ≥ 2.0 mmol/L), subclinical hypocalcemia (serum calcium concentration < 2.0 mmol/L, absence of clinical signs), and clinical hypocalcemia (clinical signs and successful treatment). An activity sensor was fitted to the right hind leg of cows 3 wk before their expected calving date. Data for lying time, standing time, number of steps, and the total number of standing and lying bouts (postural transitions) were automatically collected and summed into 15-min blocks. Behavioral variables were summarized into 2-h and 24-h periods before analyses. Mixed effect models were used to analyze cow behavior in the entire 14 d before calving (d -14 to -1), on the day of calving, and the entire 21 d postcalving (d 1 to 21). In the precalving period, multiparous cows with normocalcemia had fewer postural transitions (18.5 ± 6.9 no./d) compared with cows with subclinical hypocalcemia (23.5 ± 8.0 no./d) and clinical hypocalcemia (23.5 ± 8.6 no./d). However, there was no association between blood calcium status on lying time (min/d) or step count (no./d) for multiparous cows. For primiparous cows, the step count of cows with subclinical hypocalcemia remained constant across the period, and the step count of cows with normocalcemia decreased from 842.8 steps/d on d -14 to 427.5 steps/d on d -1. Postpartum cows with clinical hypocalcemia were less active (fewer steps) and spent 88 min/d (1.5 h) and 125 min/d (2.1 h) more time lying down compared with cows with subclinical hypocalcemia and normocalcemia, respectively. This shows that clinical hypocalcemia is associated with significant long-lasting behavioral effects on cows during the critical postpartum period.

Evaluation of biochemical profile of dairy cows with metabolic diseases in tropical conditions

The aims of this study were to characterize the biochemical profile, the reproductive performance and to identify potential predictive biomarkers of disease state of dairy cows with hyperketonemia, lipomobilization and hypocalcemia raised in tropical conditions in southeastern Brazil. Dairy cows (n = 50) were divided into a group of healthy cows (n = 14), cows with lipomobilization (n = 14), cows with hypocalcemia (n = 11), and a group of cows with hyperketonemia (n = 11). Evaluation of body condition score (BCS), body weight (BW) and blood samples was performed on 21, 14, 7, 4 and 2 days before calving, parturition, 1, 7, 14, 21, 30, 45 and 60 days post-partum and milk production was recorded on days 7, 14, 21, 30, 45 and 60 after parturition. Blood samples were assayed for aspartate aminotransferase (AST), gamma-glutammyltransferase (GGT), albumin, total protein, globulin, fibrinogen, total cholesterol, triglyceride, urea and creatinine concentrations. The biochemical profile, BCS, BW, milk production and reproductive performance differed (p < .05) among the groups. Our findings indicate changes in the biochemical profile of dairy cows with metabolic diseases and impaired production and fertility of dairy cows in this group. Variable importance in projection plots demonstrated that cholesterol, urea, total protein, albumin and fibrinogen in the serum were the strongest discriminators between cows with hypocalcemia and healthy cows; and AST, cholesterol, urea and triglycerides for cows with hyperketonemia and healthy cows; and cholesterol, urea, triglycerides, total protein and fibrinogen for lipomobilization and healthy cows, which might be useful as predictive biomarkers of the disease state.

Peripartum Ca and P homeostasis in multiparous sows fed adequate or excess dietary Ca

The recent increased prevalence of uterine prolapses in sows around parturition has led to inferences that the prolapses may be associated with hypocalcemia. However, limited data are available to support that hypocalcemia occurs in sows. Hypocalcemia in dairy cows is associated with feeding excess dietary Ca during late gestation. The excess Ca is assumed to suppress homeostatic mechanisms critical to maintain serum Ca concentrations as the Ca demand increases during the early stages of lactation. In this experiment, sows were fed diets with excess Ca during late gestation and early lactation to assess the potential development of hypocalcemia in the peripartum period. Twelve crossbred (Large White × Landrace) multiparous gestating sows were fed a control diet (CON), 0.65% Ca to 0.38% standardized total tract digestible P (STTD P) and 0.67% Ca to 0.38% STTD P in gestation and lactation diets, respectively) or a high Ca diet (HCa, 1.75% Ca to 0.46% STTD P and 1.75% Ca to 0.45% STTD P in gestation and lactation diets, respectively). The diets were fed from gestation day 86 þ ± 1 until the end of lactation (27 þ ± 2 days period). On day 112 of gestation, indwelling venous catheters were placed in each sow. Blood samples were collected at 15-min intervals within four designated times (0700, 1000, 1300 and 1700 h) on gestation day 113 and lactation days 1, 3 and 5. Venous blood pH, gases (pO2, pCO2 and HCO3-), electrolytes (K+, Na+ and Cl-), ionized Ca (iCa), metabolites (glucose and lactate), plasma total Ca (tCa), and P were analyzed. Overall, sows fed HCa diet had greater (P < 0.001) concentrations of blood iCa and plasma tCa than sows fed CON diets. No clinical signs of Ca metabolism disorders were observed. Unexpectedly, concentrations of plasma P in sows fed HCa diets were lower (P < 0.001) than in sows fed CON diets. Plasma P tended to decrease (P = 0.057) as day of lactation increased. Differences between dietary treatments for blood pH, gases, electrolytes and metabolites were not detected (P > 0.05). No evidence for hypocalcemia was detected in peripartum sows fed CON or HCa diets. These data imply that excess Ca in late gestation diets did not result in hypocalcemia during the peripartum period. Future experiments should focus on factors other than hypocalcemia to identify causes of uterine prolapses in sows.

Clinical Ketosis-Associated Alteration of Gene Expression in Holstein Cows

Ketosis is one of the most prevalent transition metabolic disorders in dairy cows, and has been intrinsically influenced by both genetic and nutritional factors. However, altered gene expression with respective to dairy cow ketosis has not been addressed yet, especially at the genome-wide level. In this study, we recruited nine Holsteins diagnosed with clinical ketosis and ten healthy controls, for which whole blood samples were collected at both prepartum and postpartum. Four groups of blood samples were defined: from cows with ketosis at prepartum (PCK, N = 9) and postpartum (CK, N = 9), respectively, and controls at prepartum (PHC, N = 10) and postpartum (HC, N = 10). RNA-Seq approach was used for investigating gene expression, by which a total of 27,233 genes were quantified with four billion high-quality reads. Subsequently, we revealed 75 and four differentially expressed genes (DEGs) between sick and control cows at postpartum and prepartum, respectively, which indicated that sick and control cows had similar gene expression patterns at prepartum. Meanwhile, there were 95 DEGs between postpartum and prepartum for sick cows, which showed depressed changes of gene expression during this transition period in comparison with healthy cows (428 DEGs). Functional analyses revealed the associated DEGs with ketosis were mainly involved in biological stress response, ion homeostasis, AA metabolism, energy signaling, and disease related pathways. Finally, we proposed that the expression level of STX1A would be potentially used as a new biomarker because it was the only gene that was highly expressed in sick cows at both prepartum and postpartum. These results could significantly help us to understand the underlying molecular mechanisms for incidence and progression of ketosis in dairy cows.

Effects of ORAI calcium release-activated calcium modulator 1 (ORAI1) on neutrophil activity in dairy cows with subclinical hypocalcemia1

Hypocalcemia in dairy cows is often associated with inflammation-related disorders such as metritis and mastitis. The protein encoded by the Ca2+ release-activated calcium modulator 1 (ORAI1) gene is a membrane Ca2+ channel subunit that is activated when Ca2+ stores are depleted. Polymorphonuclear neutrophils (PMNL) have a crucial role in the defense against infection through migration, adhesion, chemotaxis, phagocytosis, and reactive oxygen species (ROS) production in response to pathogens. Whether hypocalcemia affects the activity of PMNL and if ORAI1 is involved remains unknown. To address this, PMNL were isolated at 3 d of calving from dairy cows diagnosed as clinically healthy (n = 20, CONTROL) or with plasma concentration of calcium < 2.0 mmol/L as a criterion for diagnosis of subclinical hypocalcemia (n = 20, HYPOCAL). PMNL isolated from both groups of cows were treated with or without the sarcoendoplasmic Ca2+ ATPase inhibitor thapsigargin, Ca2+ ionophore Ionomycin, and ORAI1 blocker 2APB. The intracellular Ca2+ concentration, ORAI1 abundance, ROS, phagocytosis rate, migration, and adhering capacity of treated PMNL were evaluated. Some of the in vitro assays also included use of small interfering ORAI1 RNA (siORAI1), 100 nM 1,25(OH)2D3, or 100 nM parathyroid hormone (PTH). Intracellular Ca2+ concentration was markedly lower in HYPOCAL. In addition, ORAI1 was detected in PMNL plasma membrane via FACS and was markedly lower in cows with HYPOCAL. Migration, adhesion capacity, and phagocytosis rate of PMNL were lower in response to HYPOCAL. Furthermore, plasma and PMNL concentration of nucleosome assembly protein (NAP2) and pro-platelet basic protein (CXCL7) was markedly lower with HYPOCAL. All these changes were associated with lower ROS production by PMNL. Thapsigargin and ionomycin treatment in vitro increased ORAI1 expression, migration of PMNL, adhering capacity, phagocytosis rate, and ROS production; conversely, those effects were abrogated by siORAI1 and ORAI1 inhibitor 2APB treatment. Also cytosolic Ca2+ concentration and ORAI1 abundance were increased by 1,25(OH)2D3 and PTH supplementation. Overall, the data indicate that failure of PMNL to uptake Ca2+ due to downregulation of ORAI1 during subclinical hypocalcemia is a factor contributing to impaired PMNL function. In addition, plasma PTH or 1,25(OH)2D3 could regulate ORAI1 and also participate in the regulation of PMNL activity.

A Pilot Study To Evaluate The Effect Of A Novel Calcium And Vitamin D-Containing Oral Bolus On Serum Calcium Levels In Holstein Dairy Cows Following Parturition

Background

The initiation of lactation challenges the ability of the modern lactating cow to maintain calcium homeostasis, and typically results in a drop in blood calcium levels, leading to mobilization of calcium reserves from skeletal stores. As such, the recommendation to provide supplemental calcium at parturition to older cows has become an industry-standard practice.

Methods

Mature cows were treated at calving and 12 hrs later with either the novel calcium bolus (NB) or a commercially available calcium bolus (CB). Blood was collected from animals at 0, 1, 6, 12, 13, and 24 hrs following calving, and the resulting serum samples were analyzed.

Results

Overall, there was no statistical difference between the NB and CB groups for blood calcium levels within the first 24 hrs following parturition (P = 0.50). Cows in both groups experienced a significant increase in serum calcium by 1 hr after parturition; however, this increase was not sustained through subsequent sampling times.

Conclusion

This pilot study demonstrates that both boluses have a similar effect in the elevation of blood calcium.

Association of transient, persistent, or delayed subclinical hypocalcemia with early lactation disease, removal, and milk yield in Holstein cows

Our objectives were to evaluate the association of subclinical hypocalcemia (SCH) dynamics with the risk of early lactation disease, removal, and milk production. We conducted a prospective observational cohort study in 407 Holstein cows in 2 dairy herds in New York. Cows were stratified by parity group (144 primiparous, 263 multiparous) and classified into 1 of 4 groups based on postpartum plasma Ca concentrations previously associated with improved milk production or increased risk of disease: normocalcemic (NC; primiparous [Ca] >2.15 mmol/L at 1 and 2 d in milk, n = 67; multiparous [Ca] >1.77 at 1 d in milk and 2.20 mmol/L at 4 d in milk, n = 109); transient SCH (tSCH; primiparous [Ca] ≤2.15 at 1 d in milk and >2.15 mmol/L at 2 d in milk, n = 25; multiparous [Ca] ≤1.77 at 1 d in milk and >2.20 mmol/L at 4 d in milk, n = 50); persistent SCH (pSCH; primiparous [Ca] ≤2.15 mmol/L at 1 and 2 d in milk, n = 33; multiparous [Ca] ≤1.77 at 1 d in milk and ≤2.20 mmol/L at 4 d in milk, n = 34); or delayed SCH (dSCH; primiparous [Ca] >2.15 at 1 d in milk and ≤2.15 mmol/L at 2 d in milk, n = 19; multiparous [Ca] >1.77 at 1 d in milk and ≤2.20 mmol/L at 4 d in milk, n = 70). Evaluated outcomes were development of an adverse event [hyperketonemia (blood β-hydroxybutyrate concentration ≥1.2 mmol/L at 3, 5, 7, or 10 d in milk), metritis, displaced abomasum, or herd removal in the first 60 d in milk] and average milk yield per day across the first 10 wk of lactation. Multivariable Poisson regression was used to analyze the adverse event outcome and generalized linear mixed models for milk yield analysis. Primiparous cows with tSCH were no more likely to have an adverse event than NC cows [risk ratio = 1.3; 95% confidence interval (CI) = 0.5 to 3.2], whereas multiparous cows tended to have a higher risk for an adverse event than NC cows (risk ratio = 1.4; 95% CI = 0.9 to 2.1). However, pSCH cows were 4.1 (95% CI = 2.1 to 7.9, primiparous) and 1.8 (95% CI = 1.2 to 2.7, multiparous) times more likely, and dSCH cows 3.2 (95% CI = 1.5 to 7.0, primiparous) and 1.9 (95% CI = 1.3 to 2.6, multiparous) times more likely, to have an adverse event than NC cows. Primiparous and multiparous cows with tSCH made more milk per day than NC, pSCH, or dSCH cows across the first 10 wk of lactation. Primiparous cows averaged 28.5 ± 0.7, 31.9 ± 1.1, 29.7 ± 0.9, and 28.7 ± 1.2 kg/d, and multiparous cows averaged 44.6 ± 0.7, 49.1 ± 1.1, 46.4 ± 1.3, and 41.4 ± 0.9 kg/d for NC, tSCH, pSCH, and dSCH cows, respectively. Our results suggest that cows with tSCH adapt well to early lactation, develop fewer disease or removal events than pSCH or dSCH cows, and make more milk than NC, pSCH, or dSCH cows. Cows with pSCH or dSCH, regardless of parity group, are at an increased risk for early lactation disease or removal events.

Widespread basal cytochrome P450 expression in extrahepatic bovine tissues and isolated cells

Periparturient cattle face increased risk of both metabolic and infectious diseases. Factors contributing to this predisposition include oxidized polyunsaturated fatty acids, also known as oxylipids, whose production is altered during the periparturient period and in diseased cattle. Alterations in the production of oxylipids derived from cytochrome P450 (CYP450) enzymes are over-represented during times of increased disease risk and clinical disease, such as mastitis. Many of these same CYP450 enzymes additionally regulate metabolism of fat-soluble vitamins, such as A, D, and E. These vitamins are essential to maintaining immune health, yet circulating concentrations are diminished near calving. Despite this, a relatively small amount of research has focused on the roles of CYP450 enzymes outside of the liver. The aim of this paper is to describe the relative gene expression of 11 CYP450 in bovine tissues and common in vitro bovine cell models. Eight tissue samples were collected from 3 healthy dairy cows after euthanasia. In vitro samples included primary bovine aortic and mammary endothelial cells and immortalized bovine kidney and mammary epithelial cells. Quantitative real-time-PCR was carried out to assess basal transcript expression of CYP450 enzymes. Surprisingly, CYP450 mRNA was widely expressed in all tissue samples, with predominance in the liver. In vitro CYP450 expression was less robust, with several cell types lacking expression of specific CYP450 enzymes altogether. Overall, cell culture models did not reflect expression of tissue CYP450. However, when CYP450 were organized by activity, certain cell types consistently expressed specific functional groups. These data reveal the widespread expression of CYP450 in individual organs of healthy dairy cows. Widespread expression helps to explain previous evidence of significant changes in CYP450-mediated oxylipid production and fat-soluble vitamin metabolism in organ microenvironments during periods of oxidative stress or disease. As such, these data provide a foundation for targeted functional experiments aimed at understanding the activities of specific CYP450 and associated therapeutic potential during times of increased disease risk.

Serum calcium dynamics within the first 3 days in milk and the associated risk of acute puerperal metritis

The objectives of this study were to evaluate postpartum serum calcium dynamics for different parity groups of dairy cows and to assess whether serum calcium concentration on d 0, 1, and 3 postpartum was associated with the risk of developing acute puerperal metritis (APM). The study took place on a commercial dairy farm in northern Germany and included 4,043 Holstein dairy cows. Calving difficulties, such as dystocia, twins, or stillbirth, were recorded. Blood samples were obtained on d 0, 1, and 3 after calving for analysis of serum calcium concentration. Animals were examined daily for clinical symptoms of retained placenta, APM, mastitis, and displaced abomasum until 10 d in milk. To determine serum calcium dynamics postpartum, we performed repeated-measures ANOVA with first-order autoregressive covariance. A logistic regression model was used to evaluate the association of serum calcium concentration with the risk of developing metritis. Serum calcium concentration was affected by time relative to calving, parity, and APM. Increasing parity negatively affected serum calcium concentration on d 0 and 1. Serum calcium concentration reached its lowest level on d 1 and 3 in multiparous and primiparous cows, respectively. The concentration increased from d 1 to 3 in multiparous cows and decreased from d 0 to 3 in primiparous cows. The association of APM and serum calcium dynamics varied by parity. On d 3, serum calcium concentration was significantly lower in animals with subsequent APM than in those without APM. The overall incidence of APM was 12.0% (primiparous cows, 20.4%; multiparous cows, 8.6%). An association existed between serum calcium concentration on d 3 after calving and APM. Primiparous cows had an odds ratio of 0.12 for serum calcium concentration on d 3, indicating that a primiparous cow with serum calcium concentration of 2.5 mmol/L had a 88% lower chance of developing APM compared with a cow with a concentration of 1.5 mmol/L. Multiparous cows had an odds ratio of 0.34 for serum calcium concentration on d 3, indicating that a multiparous cow with serum calcium concentration of 2.5 mmol/L had a 66% lower chance of developing APM compared with a cow with a concentration of 1.5 mmol/L. Primiparous cows with low serum calcium concentration had the highest predicted probability of developing APM. Our results reveal a dynamic in serum calcium concentration in the first 3 d in milk. Consequently, the day of sampling and the observed risk period for hypocalcemia are important when conducting epidemiological studies to evaluate associations between hypocalcemia and clinical diseases.

Cow-level factors associated with subclinical hypocalcemia at calving in multiparous Jersey cows

The objective of our study was to identify cow-level factors associated with subclinical hypocalcemia at calving (SCH) in multiparous Jersey cows. A total of 598 Jersey and 218 Jersey × Holstein crossbreed cows from 2 commercial dairy herds were enrolled in a retrospective cohort study. Blood samples to determine total Ca concentration were collected from the coccygeal vessels at 3 h 19 min (±2 h 33 min) after calving. We used 2 serum Ca concentration thresholds to define SCH: <2.00 mmol/L (SCH-2.00) and <2.12 mmol/L (SCH-2.12). We evaluated the association of cow-level factors with SCH with multivariable Poisson regression models. Variables evaluated for association with SCH were herd; parity (2, 3, and ≥4); breed; previous lactation length and 305-d mature-equivalent milk yield; previous lactation first test milk yield and last test somatic cell count; lengths of calving interval, gestation, dry, and close-up periods; body condition and locomotion scores at calving; calving ease; and calf sex for singletons. We categorized continuous variables into quartiles (≤25th percentile, interquartile range and ≥75th percentile). The prevalence of SCH among Jersey cows was 40 (SCH-2.00) and 64% (SCH-2.12). Jersey cows of higher parity had greater risk of SCH-2.00 and SCH-2.12. The risk of SCH-2.12 was higher after birthing male calves. We also found a tendency for previous lactation length and previous lactation 305-d mature-equivalent milk yield effect to affect risk of SCH-2.12. The risk of SCH-2.12 was lower for cows that had a previous lactation length shorter than the 25th percentile compared with cows that had a previous lactation length within the interquartile range. The risk of SCH-2.12 was higher for cows that had a previous lactation 305-d mature-equivalent milk yield below the 25th percentile compared with cows that had a previous lactation 305-d mature-equivalent milk yield above the 75th percentile. Also, Jersey × Holstein crossbreed was associated with increased risk of SCH-2.00. In the multivariable analysis, we observed no association between SCH and previous lactation first test milk yield; last test somatic cell count; lengths of calving interval, gestation, dry, and close-up periods; body condition and locomotion scores at calving; and calving ease. Our study identified parity, breed, calf sex, previous lactation length, and previous lactation 305-d mature-equivalent milk yield as cow-level factors associated with SCH in multiparous Jersey cows.

Changes in the blood routine, biochemical indexes and the pro-inflammatory cytokine expressions of peripheral leukocytes in postpartum dairy cows with metritis

BACKGROUND

The aim of the present study was to clarify the changes in complete blood count, blood biochemistry, and the gene expressions of pro-inflammatory cytokines of peripheral white blood cells in postpartum dairy cows with metritis.

RESULTS

The cows were assigned to the control group (n = 28) or the metritis group (n = 28), retrospectively. Blood samples were taken 7 days before the estimated parturition (- 7 d), on the day of parturition (0 d), and 7 and 30 d after parturition. There was no difference in blood indexes between the control group and the metritis group at - 7 d. The WBC, granulocytes and monocytes were generally higher at 7 and 30 d in the metritis group than the control. In comparison with the controls, all liver function parameters and triglyceride levels at 0, 7 and 30 d, and the creatinine level at 7 and 30 d were higher in cows with metritis. The concentrations of Ca and P at 0, 7 and 30 d, and of glucose at 0 d were lower for cows in the metritis group compared with cows in the control group. Among these parameters, the WBC at 30 d, the aspartate aminotransferase activity (AST) at 7 d exceeded normal ranges (WBC: 5.0 ~ 16.0 × 10⁹/L; AST: 42.5 ~ 98 U/L), whereas the concentrations of glucose and Ca from 0 to 30 d were below normal ranges (glucose: 2.5 ~ 4.5 mmol/L; Ca: 2.2 ~ 2.5 mmol/L) in the metritis group. The gene expressions of pro-inflammatory cytokines in the metritis group were higher than those in the control group, including the IL-1α at 7d, the IL-1β at - 7, 0 and 7 d, the IL-6 at - 7, 0, 7 and 30 d, the IL-8 at 0, 7 and 30 d, and the TNF-α at 7 and 30 d.

CONCLUSION

The cows with metritis experienced systemic inflammation for 4 weeks after calving, the impaired hepatic function, and the altered metabolic status with increased triglyceride level and decreased concentrations of glucose, Ca and P.

In vivo measurement of strontium absorption from the rumen of dairy cows as an index of calcium absorption capacity

Absorption of dietary calcium from the rumen is a quantitatively important process in calcium homeostasis of ruminants. In 3 separate experiments in dairy cows, we applied a technique developed in sheep to measure the rate of strontium (Sr) absorption from the rumen as an indicator of calcium absorption capacity. Absorption from the rumen after an oral dose of SrCl₂ resulted in a maximum plasma concentration of Sr after 1 h, whereas absorption from the small intestine after injection of SrCl₂ into the abomasum through a cannula occurred more slowly. The second experiment demonstrated that the calcium absorption capacity index of the rumen was significantly greater in 21 lactating Friesian cows (230 ± 66, mean ± SEM) than in 6 mature, nonlactating, nonpregnant heifers (101 ± 21, mean ± SEM). In a third experiment, we compared clinically normal cows at the onset of lactation with those that developed parturient paresis. In cows that developed severe hypocalcemia, plasma concentrations of 1,25(OH)₂D were significantly elevated (144 ± 60 pg/mL vs. 90 ± 54 pg/mL; means ± SEM) and their rumen calcium absorption index was significantly decreased compared with that of clinically normal cows. Evidence suggested that mobilization of calcium from bone as lactation commenced was significantly depressed in paretic cows compared with those that did not show clinical signs of hypocalcemia. Moreover, ruminal stasis suppressed the absorption of calcium from the rumen. We conclude that measurement of Sr concentration in blood plasma after an oral dose of SrCl₂ into the rumen can be used as an index of rumen calcium absorption capacity under different states of calcium homeostasis.

Associations of pre- and postpartum lying time with metabolic, inflammation, and health status of lactating dairy cows

The objective was to evaluate the associations of pre- and postpartum lying time (LT) with serum total calcium (Ca), nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), and haptoglobin concentrations, hemogram, and health status of dairy cows. A total of 1,052 Holstein cattle (401 nulliparous heifers and 651 parous cows) from 3 commercial dairy farms were fitted with electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) on a hind leg 14 ± 3 d before parturition (dpp) and removed at 14 ± 3 d in milk (DIM) to assess their LT. Lying time data were summarized and reported daily (min/d or h/d). Serum concentrations of NEFA (at 14 ± 3 and 7 ± 3 dpp), total serum calcium within 48 h after calving, and BHB (at 7 ± 3 and 14 ± 3 DIM) were determined. Serum concentration of haptoglobin was determined and a hemogram was performed on a subsample of 577 cows (237 primiparous and 340 multiparous) at 7 ± 3 DIM. Cases of milk fever, retained placenta, metritis, mastitis, pneumonia, and digestive disorders within 30 DIM were recorded and cows were categorized into 1 of 4 groups: (1) nondiseased (ND, n = 613; cows without ketosis and any other health conditions); (2) cows with only ketosis (KET, n = 152); (3) sick cows experiencing ≥1 health conditions, but without ketosis (SICK, n = 198); or (4) cows with ketosis plus at least one other health condition (KET+, n = 61). Data were analyzed using mixed linear regression models or logistic regression (MIXED or GLIMMIX procedures). Lying time within 14 dpp had a significant positive quadratic association with serum NEFA concentrations at 14 ± 3 and 7 ± 3 dpp but was not significantly associated with serum Ca concentration within 48 h after calving. Lying time during the first 14 DIM after parturition had a significant linear association with the risk of ketosis within 14 DIM. For every 1-h increment in mean LT (from 8 to 15 h/d) within the first 14 DIM after calving, the risk of diagnosis with ketosis within 14 DIM increased by 3.7 percentage points. Regardless of parity, a greater proportion of KET and KET+ groups had increased serum prepartum NEFA concentration (≥400 µEq/L) and increased body condition loss from 14 dpp to 28 DIM compared with SICK and ND cows. A greater proportion of multiparous KET and KET+ cows had hypocalcemia within 48 h after calving compared with ND and SICK cows, but we did not detect a significant association between hypocalcemia and health status on primiparous cows. Multiparous KET+ cows had significantly reduced neutrophils and white blood cell count compared with ND cows, but lymphocytes did not differ. Regardless of parity, KET+ and SICK cows had significantly higher concentrations of serum haptoglobin compared with ND cows. These results suggest that LT along with energy and Ca balance are critical for transition cow health.

Short communication: Circulating serotonin is related to the metabolic status and lactational performance at the onset of lactation in dairy cows

Serotonin (5-hydroxytryptamine, 5-HT) affects many physiological functions because it is involved in glucose and lipid metabolism, calcium homeostasis, and regulation of lactation in dairy cows. This study aimed to examine physiological differences in serum 5-HT concentrations (high vs. low) and their association with metabolic status and milk production at the onset of lactation. Twelve multiparous Holstein dairy cows were milked within 4 h of calving, and blood and milk samples were collected at the first 6 subsequent milkings after parturition and at the evening milkings on d 5, 8, 10, and 14. Cows were retrospectively divided into 2 groups (6 cows/group): low serum 5-HT (LSS) and high serum 5-HT (HSS) according to their calculated areas under the curve (AUC) for serum 5-HT for the entire experimental period (cut-off: 46,000 ng/mL × 324 h). Concentrations of 5-HT, free fatty acids (FFA), β-hydroxybutyrate (BHB), glucose, calcium, and IGF-1 were measured in blood. Milk was analyzed for fat, protein, lactose, and 5-HT concentrations. Milk yield was recorded at each milking and energy-corrected milk yield was calculated. Serum 5-HT concentrations were higher in HSS than in LSS [AUC (ng/mL × 324 h): 57,830 ± 4,810 vs. 25,005 ± 5,930]. The amount of energy-corrected milk was lower in HSS than in LSS. The HSS group produced less colostrum and had decreased milk yield, specifically during the first 6 milkings. Concentrations of FFA, BHB, and glucose in plasma did not differ between groups. Concentrations of IGF-1 in serum were elevated in HSS compared with LSS throughout the experiment. Total circulating calcium concentrations in serum tended to be higher in HSS than in LSS. Milk fat and protein yields were decreased in HSS compared with LSS. Milk 5-HT decreased overall during the experimental period, with LSS maintaining higher 5-HT concentrations than HSS until d 14 of lactation. In conclusion, cows with high serum 5-HT concentrations showed a reduced metabolic load at the onset of lactation, concomitantly lower milk yield, and a reduced energy output via milk.

Associations of subclinical hypocalcemia with fertility in a herd of grazing dairy cows

The main objective was to assess the associations of subclinical hypocalcemia (SCH), diagnosed at parturition (SCH-0) and 7 d in milk (SCH-7), with fertility in a herd of grazing dairy cows. Additional objectives were to characterize Ca concentration on 0 and 7 d in milk (DIM), assessing the risk factors for SCH-0 and SCH-7 and also the relationship with health status (metritis, endometritis, subclinical ketosis, and culling). A prospective observational study was carried out in a dairy farm in Argentina. Holstein cows (n = 126) were body condition scored (BCS, 1-5) on -21 ± 3, 0, 7 ± 3, and 28 ± 7 DIM and blood was collected on 0 and 7 ± 3 DIM to determine Ca and β-hydroxybutyrate concentrations. Calcium concentrations <2.0 and <2.14 mmol/L were used to define SCH-0 and SCH-7, respectively. The associations of SCH with (1) the odds for pregnancy to first service (P1AI) and pregnancy by 100 DIM (P100) were evaluated by logistic models, (2) the services per pregnancy was evaluated by a Poisson regression model, and (3) the hazards of insemination and pregnancy were evaluated with proportional hazards regression models whereas median days from calving to first insemination and to pregnancy were estimated by Kaplan-Meier method. Additionally, Ca concentration was assessed by linear regression models, and the associations of SCH-0 and SCH-7 with the odds for metritis, endometritis, subclinical ketosis, and culling were evaluated by logistic models. Calcium concentrations were similar at 0 and 7 DIM (2.40 vs. 2.41 mmol/L, respectively); they were higher in cows calving in fall than in summer (2.58 vs. 2.24 mmol/L), and they also were higher in primiparous than in multiparous cows (2.53 vs. 2.28 mmol/L, respectively). The proportion of cows having SCH-0 and SCH-7 was 27.3 and 39.3%, respectively. Fall-calving cows had lower odds for SCH-0 [odds ratio (OR) = 0.31, 95% confidence interval (CI) = 0.12-0.86] than summer-calving cows, multiparous cows had higher odds for SCH-0 (OR = 3.96, 95% CI = 1.09-14.39) than primiparous cows, and cows with prepartum BCS ≥3.00 had higher odds for SCH-0 (OR = 4.03, 95% CI = 1.17-13.89) than in cows with BCS <3.00. Conversely, parity and prepartum BCS were not important predictors for SCH-7. Surprisingly, SCH-0 was not a risk factor for SCH-7. Cows with SCH-0 had lower odds for P1AI (OR = 0.26, 95% CI = 0.07-0.99) than normocalcemic cows, given that P1AI was 14 versus 38%, respectively. The hazard of first service was not associated with SCH-0 (hazard ratio = 1.03, 95% CI = 0.63-1.70) but cows with SCH-0 had lower hazard of pregnancy (hazard ratio = 0.39, 95% CI = 0.16-0.98) and took 32 d longer to get pregnant (105 vs. 73) than normocalcemic cows. Conversely, SCH-7 was not associated with fertility. Finally, SCH-0 and SCH-7 were associated with the odds for subclinical ketosis and metritis, respectively. In conclusion, SCH-0 but not SCH-7 is associated with reduced fertility in a herd of grazing dairy cows, but both were associated with health status.

Associations between serum calcium concentration and postpartum health and reproductive performance in dairy cows

In the present study, the aim was to evaluate the associations between serum calcium concentration after calving and serum metabolites, postpartum disorders, and reproductive performance in dairy cows. Blood samples were collected from 200 Holstein cows immediately and 1, 2, 4, 6, and 8 weeks after calving to measure serum metabolites and progesterone concentrations. Cows were divided into three groups on the basis of the mean serum calcium concentration after calving: a Low group (<7.9 mg/dL, n = 52), a Moderate group (7.9-9.6 mg/dL, n = 100), and a High group (≥9.7 mg/dL, n = 48). Total cholesterol (TCH) concentration was greater in the High group than in the Moderate group during the postpartum period (P <  0.01). The High group had greater albumin concentrations during the postpartum period (P <  0.01) and glucose concentrations after calving and 1 week postpartum (P <  0.05) than the Low and Moderate groups. The High group had a lesser incidence of retained placenta than the Low (P <  0.1) and Moderate (P <  0.01) groups, and a lesser incidence of clinical endometritis than the Moderate group (P <  0.05). The probability of resuming estrous cyclicity by 8 weeks postpartum was greater in the High group than in the Low group (hazard ratio = 3.71, P <  0.05). In conclusion, greater serum calcium concentration after calving is associated with greater serum TCH, albumin, and glucose concentrations, a lesser incidence of retained placenta, and clinical endometritis, and earlier resumption of estrous cyclicity in dairy cows.

Association of postpartum hypocalcemia with early-lactation milk yield, reproductive performance, and culling in dairy cows

Periparturient hypocalcemia is frequently observed and considered as a gateway disease that is associated with various health issues. The objective of this study was to evaluate the association of hypocalcemia with early-lactation milk yield, reproductive performance, and culling across a large number of different managerial systems. A prospective cohort study was conducted based on a convenience sample of 125 dairy herds from 8 federal states of Germany between February 2015 and August 2016. A blood sample was drawn from 1,709 animals within 48 h after parturition and analyzed for serum calcium concentration. After discarding cows (n = 283) with missing data, a total of 1,426 cows were considered for final analyses. The median time from calving to sampling was 14.0 h (interquartile range = 5.0-24.9 h). For each herd, a record of the herd management software was requested 150 d after the last cow was sampled. Serum calcium concentration of each cow was associated with early-lactation milk yield (Dairy Herd Improvement Association equivalent test 1 to 3), reproductive performance [days in milk (DIM) at first artificial insemination (AI), pregnancy at first AI, time to pregnancy within 150 DIM], and culling (until 60 DIM) data. Generalized linear mixed models were used to analyze continuous or categorical data. Shared frailty models were used for time to event data. Five different thresholds were used to define hypocalcemia. Thresholds ranged from 1.8 to 2.2 mmol/L using 0.1-mmol/L increments. Clinical hypocalcemia was defined as serum calcium concentration <2.0 mmol/L in combination with clinical signs (e.g., recumbency). The effect of hypocalcemia on milk yield was conditional on parity. In primiparous cows a serum calcium concentration <2.0 mmol/L (6.4% of cows were below this threshold) had no effect on milk production, whereas there was a tendency for multiparous cows with a serum calcium concentration <2.1 mmol/L (63.2% of cows were below this threshold) to produce 0.80 kg/d more milk compared with multiparous cows at or above the threshold. Multiparous cows suffering from clinical hypocalcemia produced 2.19 kg/d less milk compared with normocalcemic cows in early lactation. Calcium status was not associated with days to first insemination. Cows with a serum calcium concentration <1.9 mmol/L (34.6% of cows below this threshold) had decreased odds (odds ratio = 0.56) of pregnancy at first AI. A serum calcium concentration <1.8 mmol/L (24.1% of cows below this threshold) had a significant effect on time to pregnancy. Compared with animals with a serum calcium concentration ≥1.8 mmol/L, the hazard of becoming pregnant within 150 DIM was reduced when cows had a serum calcium concentration <1.8 mmol/L (hazard ratio = 0.68). Cows with a serum calcium concentration <2.0 mmol/L (44.3% of cows were below this threshold) had a 1.69 times greater hazard of being culled within the first 60 DIM compared with normocalcemic animals. The present study shows that the association of hypocalcemia with milk yield was conditional on parity and serum calcium concentration measured once within 48 h after calving. Considering reproductive performance and culling in early lactation, a negative effect of postpartum hypocalcemia was demonstrated.

Could use of Selective Serotonin Reuptake Inhibitors During Lactation Cause Persistent Effects on Maternal Bone?

The lactating mammary gland elegantly coordinates maternal homeostasis to provide calcium for milk. During lactation, the monoamine serotonin regulates the synthesis and release of various mammary gland-derived factors, such as parathyroid hormone-related protein (PTHrP), to stimulate bone resorption. Recent evidence suggests that bone mineral lost during prolonged lactation is not fully recovered following weaning, possibly putting women at increased risk of fracture or osteoporosis. Selective Serotonin Reuptake Inhibitor (SSRI) antidepressants have also been associated with reduced bone mineral density and increased fracture risk. Therefore, SSRI exposure while breastfeeding may exacerbate lactational bone loss, compromising long-term bone health. Through an examination of serotonin and calcium homeostasis during lactation, lactational bone turnover and post-weaning recovery of bone mineral, and the effect of peripartum depression and SSRI on the mammary gland and bone, this review will discuss the hypothesis that peripartum SSRI exposure causes persistent reductions in bone mineral density through mammary-derived PTHrP signaling with bone.

Interaction of 5-hydroxy-l-tryptophan and negative dietary cation-anion difference on calcium homeostasis in multiparous peripartum dairy cows

Hypocalcemia affects almost 50% of all dairy cows. Our laboratory has previously demonstrated that infusions of the serotonin precursor 5-hydroxy-l-tryptophan (5-HTP) increase circulating calcium concentrations in the Holstein transition cow. It is unknown whether feeding a negative dietary cation-anion difference (DCAD) diet alters the relationship between 5-HTP and hypocalcemia. The main objective of this study was to determine whether feeding a negative DCAD (-DCAD) diet before calving in conjunction with 5-HTP treatment could further diminish the magnitude of hypocalcemia at the time of calving. We used a randomized complete block design with a 2 × 2 factorial arrangement. Thirty-one multiparous Holstein cows were fed either a positive (+13 mEq/100 g) or negative (-13 mEq/100 g) DCAD diet 21 d before parturition and were intravenously infused daily with saline or 5-HTP (1 mg/kg) starting 7 d before the estimated date of parturition. Cows were blocked by parity and were randomly assigned to 1 of 4 treatment groups: positive DCAD plus saline, positive DCAD plus 5-HTP, negative DCAD plus saline, and negative DCAD plus 5-HTP, resulting in n = 8 per group. Total calcium (tCa), ionized calcium (iCa), and feed intake were recorded. The iCa was elevated prepartum in the -DCAD/5-HTP group compared with the other treatment groups as well as on d 0 and 1 postpartum. Although differences in tCa were not significant across the pre- or postpartum periods, tCa was numerically higher on d 0 and significantly higher on d 1 in -DCAD/5-HTP cows compared with all other groups. Prepartum the -DCAD/5-HTP treatment group ate less than the other treatment groups; however, postpartum dry matter intake differences were not significant. These findings demonstrate that feeding a -DCAD diet in conjunction with 5-HTP prepartum can increase postpartum circulating iCa concentrations and therefore diminish the magnitude of hypocalcemia at the time of parturition.

Proteomics and metabolomics characterizing the pathophysiology of adaptive reactions to the metabolic challenges during the transition from late pregnancy to early lactation in dairy cows

The transition from late pregnancy to early lactation is a critical period in a dairy cow's life due to the rapidly increasing drain of nutrients from the maternal organism towards the foetus and into colostrum and milk. In order to cope with the challenges of parturition and lactation, comprehensive adaptive reactions comprising the endocrine and the immune system need to be accomplished. There is high variation in this coping ability and both metabolic and infectious diseases, summarized as "production diseases", such as hypocalcaemia (milk fever), fatty liver syndrome, laminitis and ketosis, may occur and impact welfare, productive lifespan and economic outcomes. Proteomics and metabolomics have emerged as valuable techniques to characterize proteins and metabolite assets from tissue and biological fluids, such as milk, blood and urine. In this review we provide an overview on metabolic status and physiological changes during the transition period and the related production diseases in dairy cows, and summarize the state of art on proteomics and metabolomics of biological fluids and tissues involved in metabolic stress during the peripartum period. We also provide a current and prospective view of the application of the recent achievements generated by omics for biomarker discovery and their potential in diagnosis.

BIOLOGICAL SIGNIFICANCE

For high-yielding dairy cows there are several "occupational diseases" that occur mainly during the metabolic challenges related to the transition from pregnancy to lactation. Such diseases and their sequelae form a major concern for dairy production, and often lead to early culling of animals. Beside the economical perspective, metabolic stress may severely influence animal welfare. There is a multitude of studies about the metabolic backgrounds of such so called production diseases like ketosis, fatty liver, or hypocalcaemia, although the investigations aiming to assess the complexity of the pathophysiological reactions are largely focused on gene expression, i.e. transcriptomics. For extending the knowledge towards the proteome and the metabolome, the respective technologies are of increasing importance and can provide an overall view of how dairy cows react to metabolic stress, which is needed for an in-depth understanding of the molecular mechanisms of the related diseases. We herein review the current findings from studies applying proteomics and metabolomics to transition-related diseases, including fatty liver, ketosis, endometritis, hypocalcaemia and laminitis. For each disease, a brief overview of the up to date knowledge about its pathogenesis is provided, followed by an insight into the most recent achievements on the proteome and metabolome of tissues and biological fluids, such as blood serum and urine, highlighting potential biomarkers. We believe that this review would help readers to be become more familiar with the recent progresses of molecular background of transition-related diseases thus encouraging research in this field.