Effect of calcium-energy supplements on calving-related disorders, fertility and milk yield during the transition period in cows fed anionic diets

Effects of oral calcium on reproduction and postpartum health in cattle: a meta-analysis and quality assessment

Postpartum blood calcium (Ca) concentration is related to the reproduction and health of cattle. Oral calcium supplements were given to dairy cows after calving to increase blood Ca concentration and reduce the risk of hypocalcemia. However, studies have shown that oral Ca has different effects in preventing disease. The purposes of this study were (i) to conduct a meta-analysis to evaluate the expected effect of oral Ca on incidence of calving-related diseases, pregnancy risk and milk yield in dairy cows, and (ii) to make a quality assessment of these related studies. In total, 22 eligible studies were included in this review. Meta-analysis showed that oral Ca could significantly reduce the incidence of hypocalcemia (clinical hypocalcemia: relative risk (RR) = 0.67, 95% confidence interval (CI) = [0.52, 0.87]; subclinical hypocalcemia: RR = 0.81, CI = [0.72, 0.91]), and incidence of retained placenta (RR = 0.77, CI = [0.62, 0.95]), improved blood Ca concentrations: mean difference (MD) = 0.08; 95% CI = [0.04, 0.11]. For other results, the meta-analysis revealed a lack of evidence of the correlation between oral Ca and serum magnesium (Mg) / phosphorus (P) concentration (Mg: MD = -0.04; 95% CI = [-0.10, 0.02]; P: MD = 0.05; 95% CI = [-0.10, 0.21]) or incidence of other calving-related disorders (metritis: RR = 1.06, CI = [0.94, 1.19]; ketosis: RR = 1.04, CI = [0.91, 1.18]; mastitis: RR = 1.02, CI = [0.86, 1.21]; displacement of the abomasum: RR = 0.81, CI = [0.57, 1.16]) or pregnancy risk (pregnancy risk at first service: RR = 0.99, CI = [0.94, 1.05]; overall pregnancy rate: RR = 1.03, CI = [0.98, 1.08]) or milk yield (MD = 0.44; 95% CI = [-0.24, 1.13]). The distribution of the funnel plot formed by the included studies was symmetrical, and the Egger's test had a p > 0.05, indicating that there was no significant publication bias. Sensitivity analyses results suggested that the results of meta-analysis are robust. Quality assessment of the included studies revealed that the risk of bias was focused on selection bias, performance bias, detection bias and other sources of bias, and the future research should focus on these aspects.

Association of precalving serum NEFA concentrations with postpartum diseases and reproductive performance in multiparous Holstein cows: Cut-off values

BACKGROUND

High concentrations of NEFA relative to a defined reference or 'cut-point' values before calving can predict the risk of specific or collective periparturient disease events.

OBJECTIVES

A field-based cohort study was conducted to evaluate the value and critical points of serum nonesterified fatty acids (NEFA) at the precalving time to predict the occurrence of postpartum diseases and reproductive performance in dairy cows.

METHODS

Blood samples were taken from 521 high-yielding dairy cows at 1 week (±3 days) before calving and NEFA levels were measured. Health and reproduction information of each cow includes dystocia, retained placenta, milk fever, metritis, mastitis, pregnancy in the first insemination and pregnancy in the first two inseminations, and culling in the first 60 days of lactation and milk production.

RESULTS

Our results show that there are significant relationships between precalving NEFA with the probability of pregnancy at the first and the first two inseminations after calving. The cows that had NEFA concentrations less than 0.5 mmol/L at the last week of pregnancy were 3.51 and 3.15 times more likely to be pregnant at first insemination and the first two inseminations, respectively. Also, our results showed that there are significant relationships between precalving NEFA concentration and the likelihood of dystocia and milk fever. The probability of dystocia and milk fever occurrence were 2.56 and 1.91 times greater in those cows that had NEFA concentrations more than 0.3 mmol/L, respectively.

CONCLUSIONS

The present results indicated that Increasing NEFA during the prepartum period could adversely affect the reproductive efficiency of dairy cows.

Blood calcium dynamics in cows receiving an aqueous calcium suspension for voluntary consumption or a calcium bolus following parturition

The form of oral calcium (Ca) supplement and the Ca source influence Ca absorption dynamics resulting in different postpartum calcemia. The objective of this study was to investigate whether an oral Ca supplement (mainly CaCO3) offered for voluntary consumption would maintain or increase postpartum blood Ca to the same degree as a Ca bolus (mainly CaCl2) providing an equivalent dose of a Ca. A total of 72 Holstein cows were blocked by expected parturition date and parity. Within each block of 3 animals, cows were randomly assigned to one of three treatments, including an oral Ca supplement offered for voluntary consumption (Ca-drink, n = 23), an oral Ca bolus (Ca-bolus, n = 24), or an untreated group (CON, n = 25). Treatments were administered once within 15 min postpartum. The Ca-drink provided 45 g of Ca (CaCO3 source) and was mixed in 20 L of lukewarm water and offered to cows for 30 min. The Ca-bolus provided 43 g of Ca (71% from CaCl2 and 29% from CaSO4) and was administered once. Both Ca-bolus and CON cows received 20-l of lukewarm water at parturition to standardize the volume of fluids (Ca-drink or 20-l lukewarm water) offered at parturition. Dairy cows offered Ca-drink had a 28% higher fluid consumption than Ca-bolus and CON cows. Milk yield and milk composition expressed in percentage protein, fat, lactose, and urea did not differ, whilst there was a small but significant increase in DMI in cows receiving the Ca-drink compared to CON, while Ca-bolus did not differ from other groups. This was consistent with reduced BW losses between week 1 and 3 in cows receiving the Ca-drink suspension. Treatment by time interactions were present for blood Ca, glucose, and urea concentrations. Blood Ca was relatively stable in Ca-drink cows, while higher fluctuations were observed in Ca-bolus cows. In Ca-bolus cows, blood Ca increased from 15 min to 6 h, decreased from 6 to 24 h, and finally increased again from 24 to 48 h. At 24 h post administration, blood Ca was greater in cows receiving the Ca-drink than cows receiving the Ca-bolus. Blood glucose was greater in Ca-bolus cows at 15 min after treatment administration compared with Ca-bolus and CON, while blood urea was higher in CON than Ca-drink and Ca-bolus throughout the sampling period. These results indicate that voluntary oral Ca resulted in a relatively stable calcemia, whereas higher fluctuations were observed in cows receiving the Ca-bolus. Due to a lack of differences between Ca-drink and Ca-bolus compared with CON, it is not possible to conclude regarding the efficacy in maintaining postpartum blood Ca.

Heat Stress: Effects on Rumen Microbes and Host Physiology, and Strategies to Alleviate the Negative Impacts on Lactating Dairy Cows

Heat stress (HS) in dairy cows causes considerable losses in the dairy industry worldwide due to reduced animal performance, increased cases of metabolic disorders, altered rumen microbiome, and other health problems. Cows subjected to HS showed decreased ruminal pH and acetate concentration and an increased concentration of ruminal lactate. Heat-stressed cows have an increased abundance of lactate-producing bacteria such as Streptococcus and unclassified Enterobacteriaceae, and soluble carbohydrate utilizers such as Ruminobacter, Treponema, and unclassified Bacteroidaceae. Cellulolytic bacteria, especially Fibrobacteres, increase during HS due to a high heat resistance. Actinobacteria and Acetobacter, both acetate-producing bacteria, decreased under HS conditions. Rumen fermentation functions, blood parameters, and metabolites are also affected by the physiological responses of the animal during HS. Isoleucine, methionine, myo-inositol, lactate, tryptophan, tyrosine, 1,5-anhydro-D-sorbitol, 3-phenylpropionic acid, urea, and valine decreased under these conditions. These responses affect feed consumption and production efficiency in milk yield, growth rate, and reproduction. At the cellular level, activation of heat shock transcription factor (HSF) (located throughout the nucleus and the cytoplasm) and increased expression of heat shock proteins (HSPs) are the usual responses to cope with homeostasis. HSP70 is the most abundant HSP family responsible for the environmental stress response, while HSF1 is essential for increasing cell temperature. The expression of bovine lymphocyte antigen and histocompatibility complex class II (DRB3) is downregulated during HS, while HSP90 beta I and HSP70 1A are upregulated. HS increases the expression of the cytosolic arginine sensor for mTORC1 subunits 1 and 2, phosphorylation of mammalian target of rapamycin and decreases the phosphorylation of Janus kinase-2 (a signal transducer and activator of transcription factor-5). These changes in physiology, metabolism, and microbiomes in heat-stressed dairy cows require urgent alleviation strategies. Establishing control measures to combat HS can be facilitated by elucidating mechanisms, including proper HS assessment, access to cooling facilities, special feeding and care, efficient water systems, and supplementation with vitamins, minerals, plant extracts, and probiotics. Understanding the relationship between HS and the rumen microbiome could contribute to the development of manipulation strategies to alleviate the influence of HS. This review comprehensively elaborates on the impact of HS in dairy cows and introduces different alleviation strategies to minimize HS.

Prevention of retained fetal membranes and improvement in subsequent fertility with oxytocin administration in cows with assisted calving

In dairy cows, the efficacy of oxytocin treatment for preventing retained fetal membranes (RFM) is controversial. The physiological condition of cows associated with the calving process may affect the action of oxytocin. This study aimed to elucidate the difference in the efficacy of exogenous oxytocin treatment immediately after calving among cows that received various obstetric interventions. The calving ease was recorded using a score of 1-5, and assisted birth was defined as a score of 2 or more. Cows that required calving assistance (assisted, n = 28) due to delayed calving progression had a prolonged time from calving to expulsion of the fetal membrane (P < 0.01), and impaired reproductive performance compared to cows that did not receive calving assistance (unassisted, n = 78). The effect of oxytocin treatment was determined using cows that did not expel their fetal membrane within 3 h after calving. Cows were randomly divided into the control (unassisted, n = 41; assisted, n = 22) or oxytocin group (unassisted, n = 33; assisted, n = 10). Oxytocin (50 IU) was administered intramuscularly to the cows in the oxytocin group between 3 and 6 h after calving, while no treatment was administered in the control group. In cows with assisted birth, oxytocin administration accelerated placental expulsion (P < 0.05) and improved several reproductive parameters, such as the number of services until conception (P < 0.05) and the calving to conception intervals (P < 0.05) compared to the control group. On the other hand, oxytocin administration slightly accelerated placental expulsion (P < 0.05), but failed to improve fertility in cows with unassisted birth. The results indicate that the action of oxytocin varies depending on the calving situation of the cows. Oxytocin administration during the early postpartum period could prevent RFM and improve the decline in reproductive performance associated with calving assistance.

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.

Glucose Metabolism and Dynamics of Facilitative Glucose Transporters (GLUTs) under the Influence of Heat Stress in Dairy Cattle

Heat stress is one of the main threats to dairy cow production; in order to resist heat stress, the animal exhibits a variety of physiological and hormonal responses driven by complex molecular mechanisms. Heat-stressed cows have high insulin activity, decreased non-esterified fatty acids, and increased glucose disposal. Glucose, as one of the important biochemical components of the energetic metabolism, is affected at multiple levels by the reciprocal changes in hormonal secretion and adipose metabolism under the influence of heat stress in dairy cattle. Therefore, alterations in glucose metabolism have negative consequences for the animal’s health, production, and reproduction under heat stress. Lactose is a major sugar of milk which is affected by the reshuffle of the whole-body energetic metabolism during heat stress, contributing towards milk production losses. Glucose homeostasis is maintained in the body by one of the glucose transporters’ family called facilitative glucose transporters (GLUTs encoded by SLC2A genes). Besides the glucose level, the GLUTs expression level is also significantly changed under the influence of heat stress. This review aims to describe the effect of heat stress on systemic glucose metabolism, facilitative glucose transporters, and its consequences on health and milk production.

Nutritional Physiology and Biochemistry of Dairy Cattle under the Influence of Heat Stress: Consequences and Opportunities

Simple Summary

Modern dairy cows have elevated internal heat loads caused by high milk production, and the effects of accumulating incremental heat are exacerbated when temperature and humidity increases in the surroundings. To shed this additional heat, cows initiate a variety of adaptive mechanisms including increased respiration rate, panting, sweating, reduced milk yield, vasodilatation, and decreased reproductive performance. Hormonal changes based on reciprocal alterations to the energetic metabolism are particularly accountable for reduced efficiency of the dairy production under the heat stress. As animals experience negative energy balance; glucose, which is also a precursor of milk lactose, becomes the preferential energy fuel. In the absence of proper mitigations, heat stress possesses potential risk of economic losses to dairy sector. Besides physical measures for the timely prediction of the actual heat stress coupled with its proper amelioration, nutritional mitigation strategies should target modulating energetic metabolism and rumen environment.

Abstract

Higher milk yield and prolificacy of the modern dairy cattle requires high metabolism activities to support them. It causes high heat production by the body, which coupled with increasing environmental temperatures results in heat stress (HS). Production, health, and welfare of modern cattle are severely jeopardized due to their low adaptability to hot conditions. Animal activates a variety of physiological, endocrine, and behavioral mechanisms to cope with HS. Traditionally, decreased feed intake is considered as the major factor towards negative energy balance (NEBAL) leading to a decline in milk production. However, reciprocal changes related to insulin; glucose metabolism; failure of adipose mobilization; and skeletal muscle metabolism have appeared to be the major culprits behind HS specific NEBAL. There exists high insulin activity and glucose become preferential energy fuel. Physiological biochemistry of the heat stressed cows is characterized by low-fat reserves derived NEFA (non-esterified fatty acids) response, despite high energy demands. Besides these, physiological and gut-associated changes and poor feeding practices can further compromise the welfare and production of the heat-stressed cows. Better understanding of HS specific nutritional physiology and metabolic biochemistry of the dairy cattle will primarily help to devise practical interventions in this context. Proper assessment of the HS in cattle and thereby applying relevant cooling measures at dairy seems to be the basic mitigation approach. Score of the nutritional strategies be applied in the eve of HS should target supporting physiological responses of abatement and fulfilling the deficiencies possessed, such as water and minerals. Second line of abatement constitutes proper feeding, which could augment metabolic activities and synergizes energy support. The third line of supplemental supports should be directed towards modulating the metabolic (propionates, thiazolidinediones, dietary buffers, probiotics, and fermentates) and antioxidant responses (vitamins). Comprehensive understanding of the energetic metabolism dynamics under the impact of incremental heat load and complete outlook of pros and cons of the dietary ameliorating substances together with the discovery of the newer relevant supplementations constitutes the future avenues in this context.

Genetic parameters of subclinical macromineral disorders and major clinical diseases in postparturient Holstein cows

The main objective of this study was to assess the genetic parameters of subclinical disorders associated with subclinical hypocalcemia, hypophosphatemia, subclinical hypomagnesemia, hypokalemia, and hyperphosphatemia, as well as major clinical diseases after calving in Holstein cows. The secondary objective was to estimate the associated genetic and phenotypic correlations among these subclinical and clinical conditions after calving in Holstein cows. The study was conducted in 9dairy herds located in Northern Greece. None of the herds used any kind of preventive measures for milk fever (MF). A total of 1,021 Holstein cows with pedigree information were examined from November 2010 until November 2012. The distribution across parities was 466 (parity 1), 242 (parity 2), 165 (parity 3), and 148 (parity 4 and above) cows. All cows were subjected to a detailed clinical examination and blood was sampled on d 1, 2, 4, and 8 after calving. Serum concentrations of Ca, P, Mg, and K were measured in all samples, whereas β-hydroxybutyrate (BHB) was measured only for d 8. The final data set included 4,064 clinical and 16,848 biochemical records (4,020 Ca, 4,019 P, 4,020Mg, 3,792K, and 997 BHB). Data of 1,988 observations of body condition score at d 1 and 8 were also available. All health traits were analyzed with a univariate random regression model. The genetic analysis for macromineral-related disorders included 986 cows with no obvious signs of MF (35 cows with MF were excluded). Analysis for other health traits included all 1,021 cows. A similar single record model was used for the analysis of BHB. Genetic correlations among traits were estimated with a series of bivariate analyses. Statistically significant daily heritabilities of subclinical hypocalcemia (0.13-0.25), hypophosphatemia (0.18-0.33), subclinical hypomagnesemia (0.11-0.38), and hyperphosphatemia (0.14-0.22) were low to moderate, whereas that of hypokalemia was low (0.08-0.10). The heritability of body condition score was 0.20±0.10. Statistically significant daily heritabilities of clinical diseases were those of MF (0.07-0.11), left displaced abomasum (0.19-0.31), and mastitis (0.15-0.41). Results suggest that these health disorders are heritable traits and could be minimized with proper genetic selection. Statistically significant phenotypic correlations were estimated for the first time between macromineral concentrations and almost all transition cow metabolic and infectious health disorders.

Effects of oral calcium supplementation on productive and reproductive performance in Holstein cows

The objectives of this experiment were to determine the effects of oral Ca supplementation on milk yield, body condition, pregnancy per artificial insemination (P/AI), and days to pregnancy in Holstein cows considered to be of low (LRM; no calving assistance, live singleton without retained placenta) or high (HRM; at least one of the following: dystocia, twins, stillbirth, retained placenta, or vulvo-vaginal laceration) risk of developing metritis. The hypotheses were that oral Ca supplementation during the early postpartum period would reduce the loss of body condition and improve lactation performance and reproduction. Four hundred fifty Holstein cows were blocked by parity as primiparous cows (n=174) or multiparous cows (n=276). Within parity, a cow considered at HRM was matched with a cow of LRM and the pair was randomly assigned to control (no Ca supplementation), 86g of Ca on d 0 and 1 postpartum (CaS1), or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Body condition was scored at calving and 32 d postpartum and estrous cyclicity was evaluated at 38 and 52 d postpartum. Milk yield was recorded daily. Multiparous cows were classified as above or below the mean 305-d mature equivalent milk yield based on production in the previous lactation. Reproductive performance was evaluated for the first 210 d postpartum. Body condition did not differ among treatments, and cows lost on average 0.44 units of body condition in the first month of lactation. Calcium supplementation did not affect milk yield in the first 5 mo postpartum. For multiparous cows, Ca supplementation was beneficial to milk yield in the first 30 DIM in cows of greater production potential, but detrimental to multiparous cows with below average production potential. Calcium supplementation to primiparous cows reduced P/AI at first (control=55.8, CaS1=31.5, CaS4=37.0%) and all artificial inseminations (control=48.5, CaS1=34.6, CaS4=38.5%); however, Ca supplementation to multiparous cows improved P/AI at the first (control=32.1, CaS1=38.6, CaS4=41.3%) and all artificial inseminations (control=28.1, CaS1=35.3, CaS4=40.5%). These responses in P/AI to Ca supplementation resulted in extended median days to pregnancy (control=75, CaS1=100, CaS4=94 d) and smaller proportion of pregnant cows (control=89.3, CaS1=83.9, CaS4=83.9%) in primiparous cows, but shorter days to pregnancy (control=115, CaS1=94, CaS4=94 d) and increased proportion of pregnant cows in multiparous cows (control=67.0, CaS1=77.2, CaS4=74.3%). Risk of metritis depressed most measures of reproduction evaluated in the experiment. Results indicate that responses to oral Ca supplementation are conditional on parity and production potential of cows. Oral Ca supplementation was detrimental to reproduction in primiparous cows. On the other hand, Ca supplementation benefited reproduction in multiparous cows and milk yield in the cohort of multiparous cows of greater production potential.

The effect of intrauterine infusion of dextrose on clinical endometritis cure rate and reproductive performance of dairy cows

The main objective of this study was to evaluate the intrauterine administration use of 200 mL of 50% dextrose solution as a treatment against clinical endometritis (CE); CE cure rate and reproductive performance were evaluated. Additionally, the association of several relevant risk factors, such as retained placenta (RP), metritis, CE, anovulation, hyperketonemia, and body condition score with reproductive performance, early embryonic mortality, and CE were evaluated. A total of 1,313 Holstein cows housed on 4 commercial dairy farms were enrolled in the study. At 7±3 DIM cows were examined for metritis and had blood collected to determine serum β-hydroxybutyrate concentration. To determine if cows had ovulated at least once before 44±3 DIM, the presence of a corpus luteum was evaluated by ovarian ultrasonography at 30±3 DIM and at 44±3 DIM. At 30±3 DIM, CE was diagnosed using the Metricheck device (SimcroTech, Hamilton, New Zealand); cows with purulent or mucopurulent vaginal discharge were diagnosed as having CE. Cows diagnosed with CE (n=175) were randomly allocated into 2 treatment groups: treatment (intrauterine infusion of 200 mL of 50% dextrose) or control (no infusion). Clinical endometritis cows were re-evaluated as described above at 44±3 DIM, and cows that were free of purulent or mucopurulent vaginal discharge were considered cured. Intrauterine infusion of dextrose tended to have a detrimental effect on CE cure rate, and treatment did not have an effect on first-service conception rate and early embryonic mortality. A multivariable Cox's proportional hazard model was performed to evaluate the effect of several variables on reproductive performance; the variables RP, CE, parity, anovulation, and the interaction term between parity and anovulation were associated with hazard of pregnancy. Cows that did not have RP or CE were more likely to conceive than cows that were diagnosed with RP or CE. Cows that had RP were at 3.36 times higher odds of losing their pregnancy than cows that did not have RP. In addition, cows diagnosed with CE were at 2.16 higher odds of losing their pregnancy than cows without CE. In conclusion, intrauterine infusion of 200 mL of 50% dextrose solution as a treatment for CE had a strong statistical tendency to decrease CE cure rate, did not improve first-service conception rate and early embryonic mortality, and did not decrease calving-to-conception interval.

The effect of a monensin controlled-release capsule on the incidence of retained fetal membranes, milk yield and reproductive responses in Holstein cows

The objective of this study was to determine the effect of a monensin controlled-release capsule on the incidence of retained fetal membranes (RFM), milk yield and conception rate at first service (CRFS). The study was conducted during May to August 2004 in a large dairy herd in Chihuahua, Mexico. Cows (n = 2,025) from 20 to 30 d before expected parturition were randomly assigned to either a treatment or a control group. The treated group (n = 1,010) received orally a capsule of monensin that released 335 mg/d for 95 d. Control cows (no capsule, n = 1,015) were randomly assigned and matched by parity. Outcome variables were the incidence of RFM, first three test day milk and CRFS. Monensin decreased the incidence of RFM by 3.9% only in multiparous cows. Therefore, multiparous cows treated with monensin were 0.78 times (95% C.I. = 0.71-0.86) as likely as control multiparous cows to develop RFM. Overall, milk yield was negatively affected by the RFM condition, but it was improved by monensin only in multiparous cows with RFM at test day 1. Conception rate at first service was depressed by 10.6% in multiparous cows with RFM. However, in RFM cows treated with monensin, CRFS improved to the level of treated cows without RFM.

Effect of administration of a controlled-release monensin capsule on incidence of calving-related disorders, fertility, and milk yield in dairy cows

OBJECTIVE

To determine the effect of a controlled-release monensin capsule administered at cessation of lactation on incidence of calving-related disorders, fertility, and milk yield in dairy cows.

ANIMALS

290 dairy cows treated with monensin and 290 untreated control cows.

PROCEDURE

Treated cows received a capsule that released monensin at 335 mg/d for 95 days. Incidence of calving-related disorders; daily milk yield up to 20 days postpartum; test-day milk yield, fat, protein, and mature-equivalent 305-day milk production; and body condition score at calving were determined. Reproductive variables were conception rate at first service, pregnancy rate, and calving-to-conception interval.

RESULTS

Cows treated with monensin were 2.1 times as likely to develop dystocia and 0.8 times as likely to develop metritis as control cows. For milk yield, there was an interaction of treatment X time X parity. In multiparous cows, monensin significantly improved milk yield at test days 4 and 7. In addition, monensin increased body condition score at calving.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite increasing the likelihood of developing dystocia and metritis, administration of monensin improved the lactational performance of multiparous cows and may be a promising additive for use at the time of cessation of lactation.

How to Improve Reproductive Efficacy from Now in Japan? Find out the Factors of Late Lactation to Predict Postpartum Reproductive Diseases

Reproductive efficiency and performance in dairy cattle has been declining over the last 20 years in Japan. Recently, this has resulted in serious problems in dairy herds. There have been changes in the animals themselves and in the animal's environment, e.g. the genetic potential for milk yield has improved, the herd size of dairy farms has been expanding, the housing system of dairy cattle has been changing from tie stall to free stall, and total mixed ratio (TMR) feeding systems have become widespread. It is not clear whether the animals have adapted adequately to these environmental changes. Up till now, reproductive management has been undertaken by monitoring animal performance and/or hormonal treatments, and this has resulted in acceptable reproductive performance. However, conception and pregnancy rates have continued to decline, and the calving to calving interval has continued to extend. Consequently, the average parity and the average age at culling in dairy cattle have been declining. The most common causes of culling in dairy cattle are reproductive disorders in Japan. Therefore, in future, prevention of reproductive disorders will be required for both reproductive efficiency and animal welfare. During late pregnancy and the transition from the pregnant, non-lactating state to the non-pregnant, lactating state, dramatic changes are occurring in the dam including an increase in the fetal-placental mass and calving. Thus, the demand for energy, protein and minerals by the conceptus increases, the space within the abdominal cavity and the rumen capacity decreases due to the increased volume of the conceptus, the local immunological relationship between the fetal and maternal placenta dramatically changes, and physiological homeostasis is activated to adapt to these changes. If cattle can't maintain homeostasis before calving, the incidence of reproductive diseases will be greatly increased. We have been examining reproductive, nutritional and immunological factors to predict the occurrence of reproductive disorders as early as possible and to develop strategies to prevent them. It is unlikely that all dairy farms in Japan will be able to improve reproductive performance with general advice, due to the wide variation in feeding systems and management in Japan. Therefore, specific advice needs to be tailored to each herd, based on management systems employed within each herd. We have proposed that it is important to identify common risk factors across herds, to use these factors as an index for disease control and reproductive management and finally to demonstrate the relationship between these factors and fundamental improvement of the reproductive efficiency. We propose this approach with the aim of providing a breakthrough in improving reproductive performance in dairy cattle in Japan. The focus of this review will be that such an approach is important for improvement of the reproductive efficiency in Japanese dairy cows.

Metabolic Predictors of Displaced Abomasum in Dairy Cattle

The objective of this field study was to identify metabolic tests available in clinical practice that identified cows at increased risk of left displaced abomasum (LDA). A technician visited 1044 cows in 20 herds weekly from 1 wk before expected calving until 1 wk postpartum. Cows were assigned a body condition score and samples were collected at each visit for measurement of serum nonesterified fatty acids (NEFA), cholesterol, beta-hydroxybutyrate (BHBA), glucose, urea, calcium, and phosphorus, and a milk sample was collected postpartum for measurement of BHBA. The probability of LDA was modeled with multivariable logistic regression accounting for clustering. There were 53 cases of LDA (incidence risk = 5.1%) and the median time of diagnosis was 11 d in milk. In cows with LDA, mean NEFA concentrations began to diverge from the mean in cows without LDA 14 d before calving, whereas mean serum BHBA concentrations did not diverge until the day of calving. Prepartum, only NEFA concentration was associated with risk of subsequent LDA. Between 0 and 6 d before calving, cows with NEFA concentration > or =0.5 mEq/L were 3.6 times more likely to develop LDA after calving. For prospective application, among samples taken 4 to 10 d before expected calving, the optimum NEFA cut-point remained 0.5 mEq/L. The sensitivity, specificity, and likelihood ratio (LR) were 46%, 82%, and 2.6, respectively. Between 1 and 7 d postpartum, retained placenta, metritis, and increasing serum concentrations of BHBA and NEFA were associated with increased risk of subsequent LDA. However, considered separately, postpartum serum BHBA was a more sensitive and specific test than NEFA concentration. The odds of LDA were 8 times greater in cows with serum BHBA > or =1200 micromol/L (LR = 3.5). Cows with milk BHBA concentration > or =200 micromol/L were 3.4 times more likely to develop LDA. Serum calcium concentration was not associated with LDA. Strategic use of metabolic tests to monitor transition dairy cows should focus on NEFA in the last week prepartum and BHBA in the first week postpartum.