Associations between herd characteristics and reproductive efficiency in dairy herds

Evaluation of a Commercial Pregnancy Test Using Blood or Plasma Samples in High-Producing Dairy Cows

This study evaluated a commercial pregnancy-associated glycoproteins (PAGs)-based pregnancy test using whole blood or plasma samples during early pregnancy (28-55 days of gestation) in high-producing dairy cows. Transrectal ultrasonography was used as the gold standard method. The study population constituted of 284 cows. False positive diagnoses were recorded from Day 60 to 89 and from Day 60 to 99 postpartum in blood and plasma samples, respectively. In early pregnancy screening, correct positive diagnoses were recorded in 75% and 100% of blood and plasma samples, respectively. High milk production was associated with negative results in blood samples and with the lowest test line intensity in plasma samples. False positive or negative diagnoses were recorded in 0% of both types of samples in cows previously diagnosed as pregnant and showing signs of estrus. In conclusion, the use of plasma was more effective than the use of blood in early pregnancy diagnosis. In cows previously diagnosed as pregnant and showing signs of estrus, both types of samples showed the same results. Because of large individual variations, normal single pregnancies could not be differentiated from twin pregnancies, from pregnancies with a recently dead conceptus, or from pregnancies that experienced subsequent pregnancy loss.

Relationship between reproductive and productive traits in Holstein cattle using multivariate analysis

Multivariate procedures are used for the extraction of variables from the correlation matrix of phenotypes in order to identify those traits that explain the largest proportion of phenotypic variation and to evaluate the relationship structure between these traits. The reproductive traits (days from calving to first estrus [CFE], days from calving to last service [CLS], calving interval [CI] and gestation length [GL]) and milk production traits (milk yield at 305 days of lactation [MY305], peak yield [PY] and milk yield per day of calving interval [MYCI]) of 5,217 Holstein females (primiparous and multiparous) were measured. Principal component analysis (PCA) and factor analysis of the correlation matrix were used to estimate the correlation between traits. Analysis grouped the seven traits into three principal components and four latent factors that retained approximately 81.5% and 88.9% of the total variation of the data, respectively. The production variables exhibited positive phenotypic correlation coefficients of high magnitude (>.67). The phenotypic correlation estimates between the productive and reproductive traits were low, ranging from .13 to .22. A strong association (.99) was observed between CLS and CI. Our results indicate that multivariate analysis was effective in generating correlations between the traits studied, grouping the seven traits in a smaller number of variables that retained approximately 81% of the total variation of the data.

Survey of management practices used by Brazilian dairy farmers and recommendations provided by 43 dairy cattle nutritionists

This work aimed to survey management practices used by dairy farmers and to report nutritional recommendations adopted by 43 dairy cattle nutritionists in Brazil. The web-based survey consisted of 80 questions. Almost 50% of the participants had clients that produce <1000 kg of milk daily and 48.8% had clients who own fewer than 100 dairy cows. Corn was the primary source of grain (97.4%), and 43.9% of the nutritionists included from 41% to 50% concentrate in lactation diets. The mean roughage inclusion in lactation diets was 50.5% and 79% of the nutritionists reported corn silage as the primary roughage source. Average crude protein and rumen-degradable protein concentrations recommended by the nutritionists for lactation diets were 15.7% and 9%, respectively. Average Ca and P concentrations recommended for lactation diets were 0.70% and 0.41%, respectively. The major health problem reported by 83.9% of the nutritionists was mastitis. The present survey provides an overview of management practices adopted by dairy farmers and nutritional recommendations currently applied by dairy cattle nutritionists in Brazil. The most critical points identified were low milk yield, mastitis as the major health problem, lack of proper mixing and delivery of rations, and destination of male calves.

The effects of building design on hazard of first service in Norwegian dairy cows

Reproductive inefficiency is one of the major production and economic constraints on modern dairy farms. The environment affects onset of ovarian activity in a cow postcalving and influences estrus behavior, which in turn affects a stockperson's ability to inseminate her at the correct time. This study used survival analysis to investigate effects of building design and animal factors on the postpartum hazard of first service (HFS) in freestall-housed Norwegian Red cows. The study was performed on 232 Norwegian dairy farms between 2004 and 2007. Data were obtained through on farm measurements and by accessing the Norwegian Dairy Herd Recording System. The final data set contained data on 38,436 calvings and 27,127 services. Univariate Cox proportional hazard analyses showed that herd size and milk yield were positively associated with HFS. Total free accessible area and free accessible area available per cow year were positively associated with the HFS, as was the number of freestalls available per cow. Cows housed on slatted floors had a lower HFS than those housed on solid floors. Conversely, cows housed on rubber floors had a higher HFS than cows on concrete floors. Dead-ending alleyways reduced the hazard of AI after calving. A multivariable Cox proportional hazards model, accounting for herd management by including a frailty term for herd, showed relationships between hazard of postpartum service and explanatory variables. Animals in herds with more than 50 cows had a higher HFS [hazard ratio (HR)=3.0] compared with those in smaller herds. The HFS was also higher (HR=4.3) if more than 8.8 m(2) of space was available per cow year compared with herds in which animals had less space. The HFS after calving increased with parity (parity 2 HR=0.5, parity ≥3 HR=1.7), and was reduced if a lactation began with dystocia (HR=0.82) or was a breed other than Norwegian Red (HR=0.2). The frailty term, herd, was large and highly significant indicating a significant proportion of the variation resides at herd level. The hazard of first insemination decreased with time for all predictive variables, except dystocia. This study shows that providing adequate environmental conditions for estrus behavior is imperative for reproductive efficiency and after herd management factors and time from calving have been accounted for. Thus, optimizing building design for reproductive efficiency is of significant importance when constructing new cattle housing.

Factors affecting reproductive performance of dairy cows in a pasture-based, automatic milking system research farm: a retrospective, single-cohort study

A retrospective, single-cohort study was conducted to identify production and health factors associated with reproductive performance in a pasture-based, automatic milking system research farm. The calving system of this herd shifted from split calving to year-round calving gradually during the study period. Data from 365 cows with 798 lactations were analysed. Reproductive outcome variables of interest were intervals from calving to first oestrus, to first insemination, and to conception, as well as number of inseminations per conception, probability of submission for insemination by 80 days in milk, probability of conception by 100 days in milk and probability of conception at first insemination. Production factors (milk yield and its composition, milking frequency), record of periparturient disease, parity and season of calving were considered as predictor variables. The associations between predictor and outcome variables were assessed by multivariable linear regression, logistic regression and survival analyses, for quantitative, binary and time-to-event outcomes, respectively. Average milk yield and milking frequency during 100 days in milk were not significantly associated with any of the reproductive measures. The likelihood of conception by 100 days in milk decreased gradually with year of automatic milking system commissioning. Cows calved in autumn were 43% (hazard ratio 1.43, P < 0.05) more likely to conceive than cows calved in summer. Multiparous cows were more likely (P < 0.05) to be recorded for oestrus than primiparous cows. Twinning was negatively associated with the reproductive outcomes measured in the automatic milking system research herd. Milk yield and milking frequency during 100 days in milk had no effect on reproductive measures in the pasture-based, automatic milking system research herd.

Estimation of genetic parameters of fertility traits in Chinese Holstein cattle

Guo, G., Guo, X., Wang, Y., Zhang, X., Zhang, S., Li, X., Liu, L., Shi, W., Usman, T., Wang, X., Du, L. and Zhang, Q. 2014. Estimation of genetic parameters of fertility traits in Chinese Holstein cattle. Can. J. Anim. Sci. 94: 281–285. The objective of this study was to estimate genetic parameters for fertility traits in Chinese Holstein heifers and cows. Data of 20169 animals with 42106 records over a period of 10 yr (2001–2010) were collected from Sanyuan Lvhe Dairy Cattle Center in Beijing, China. Traits included age at first service (AFS), number of services (NS), days from calving to first service (CTFS), days open (DO), and calving interval (CI). Genetic parameters were estimated with multiple-trait animal model using the DMU software. Heritability estimates for AFS, NS, CTFS, DO and CI were 0.100±0.012, 0.040±0.017, 0.034±0.011, 0.053±0.019 and 0.056±0.014, respectively. Genetic correlations between traits observed ranged from −0.13 to 0.99. Genetic correlations between AFS with NS, CTFS, DO and CI were −0.31, 0.15, −0.13 and −0.15, respectively. Calving interval was strongly correlated with NS, CTFS and DO (0.49–0.99), and DO showed strong correlation with NS and CTFS (0.49 and 0.58, respectively). The genetic correlation between CTFS and NS was negative moderate (−0.25). Results were in range with previous literature estimates and can be used in Chinese Holstein genetic evaluation for fertility traits.

Factors influencing the chance of cows being pregnant 30 days after the herd voluntary waiting period

The objective of this study was to study factors affecting a reproductive performance indicator at the cow level adjusted for herd management strategy. Associations between the outcome variable, pregnant or not at the herd voluntary waiting period (VWP) plus 30d (pregnant at VWP+30), and the predictor variables were analyzed using a multivariable, generalized estimation equations model that adjusted for clustering of the data at the herd level. The statistical analysis was stratified on parity. In total, 132,721 cows were retained for analyses, of which 29,113 (22%) were pregnant at VWP+30d. Of the nonpregnant cows, 81,483 cows had records of artificial inseminations (AI) and 22,125 cows had no records of AI. The chance of pregnancy was higher for cows of the Swedish Red and for other/crossbreeds compared with Swedish Holstein, for cows from herds with high heat detection efficiency compared with cows from herds with medium and low heat detection efficiency, for cows from herds with long VWP (i.e., >51d) compared with cows from herds with short VWP (<51d), and for cows in freestalls compared with cows in tiestalls. The chance for pregnancy was lower for cows with severe problems at claw trimming compared with cows with no problems at trimming (only for second- and higher-parity cows), for cows that had a record of reproduction-related disease, for cows that had a record of any other disease compared with cows without record, for second- and higher-parity cows with records of dystocia compared with cows with no record of dystocia, for first-parity cows in the group with the highest milk yield compared with first-parity cows in the group with the lowest milk yield, for cows of third and higher parity in the group with the lowest milk yield compared with cows in higher yielding groups, for cows bred in summer compared with those bred in winter-spring (not significant for first-parity cows), and for cows with a twin birth had compared with cows with a single birth. We observed associations of the dose-response type, such that when the milk fat-to-protein ratio increased, the chance for pregnancy decreased, and as the somatic cell count increased, the chance for pregnancy decreased. In conclusion, factors that are known to affect reproductive efficiency also affect the chance of cows being pregnant at the herd VWP plus 30d.

Hierarchical Bayesian modeling of heterogeneous cluster- and subject-level associations between continuous and binary outcomes in dairy production

The augmentation of categorical outcomes with underlying Gaussian variables in bivariate generalized mixed effects models has facilitated the joint modeling of continuous and binary response variables. These models typically assume that random effects and residual effects (co)variances are homogeneous across all clusters and subjects, respectively. Motivated by conflicting evidence about the association between performance outcomes in dairy production systems, we consider the situation where these (co)variance parameters may themselves be functions of systematic and/or random effects. We present a hierarchical Bayesian extension of bivariate generalized linear models whereby functions of the (co)variance matrices are specified as linear combinations of fixed and random effects following a square-root-free Cholesky reparameterization that ensures necessary positive semidefinite constraints. We test the proposed model by simulation and apply it to the analysis of a dairy cattle data set in which the random herd-level and residual cow-level effects (co)variances between a continuous production trait and binary reproduction trait are modeled as functions of fixed management effects and random cluster effects.

Effect of supplemental feeding with glycerol or propylene glycol in early lactation on the fertility of Swedish dairy cows

The aim of this field study was to evaluate the effect of supplemental feeding with glycerol (GLY) or propylene glycol (PG) during early lactation on the fertility of Swedish dairy cows. Within 17 commercial dairy herds, 798 cows were randomized to three groups that were daily fed supplements with 450 g GLY, 300 g PG or nothing (control, C). The supplements were given twice daily during 0-21 days in milk as a top dress on concentrates. Data on calving date, insemination dates, gynaecological examinations, as well as breed, parity and monthly milk yield were collected. From a subset of 308 cows in seven herds, milk samples for progesterone analysis were taken twice weekly and used to determine the time for onset of luteal activity. The effects of supplements on the intervals from calving to first luteal activity (FLA), first AI (FAI) and conception (CON), respectively, were analysed using semi-parametric survival models (Cox proportional hazards models) controlling for the effect of parity, breed, calving season, milk yield and the clustering effect of herd. There was no difference in time to FLA between the cows in group C and in group GLY or PG. No differences in time to FAI or in time to CON were found between cows in group PG and group C. However, cows in the GLY group tended to get their FAI later compared with cows in the control group but without at subsequent delaying of time to CON.

A review of the causes of poor fertility in high milk producing dairy cows

Fertility in dairy cows has declined over the past five decades as milk production per cow has increased. Many hypotheses have been proposed to explain this including issues of genetics, physiology, nutrition and management, and these factors have been investigated at the animal, organ and cellular level at critical time points of the productive life of dairy cows. This paper reviews the physiological events and their causes and consequences affecting fertility in dairy cows and summarises these in a downloadable poster. We consider the following points to have the greatest negative impact on fertility and that they need to be prioritised in efforts to ameliorate the problem (others have been included in the review). Firstly, minimise negative energy balance and resolve any infection of the post partum uterus. Secondly, expression and detection of oestrus followed by insemination with high quality semen (day 0). Thirdly, ovulation and fertilisation of a high quality oocyte (day 1). Fourthly, an early increase in progesterone secretion from the corpus luteum (days 3–7). Fifthly, the uterine endometrium must produce an early and appropriate environment to stimulate embryo development (days 6–13). This leads to sixthly, a large embryo producing adequate quantities of interferon tau (days 14–18) that alters uterine prostaglandin secretion and signals maternal recognition of pregnancy (days 16–18). Future strategies to improve dairy cow fertility are needed for the benefit of the dairy industry and for cow welfare and should be based upon an integrative approach of these events.

Reproductive performance, udder health, and antibiotic resistance in mastitis bacteria isolated from Norwegian Red cows in conventional and organic farming

Background

The objectives of this study were to investigate whether there were differences between Norwegian Red cows in conventional and organic farming with respect to reproductive performance, udder health, and antibiotic resistance in udder pathogens.

Methods

Twenty-five conventional and 24 organic herds from south-east and middle Norway participated in the study. Herds were matched such that geographical location, herd size, and barn types were similar across the cohorts. All organic herds were certified as organic between 1997 and 2003. All herds were members of the Norwegian Dairy Herd Recording System. The herds were visited once during the study. The relationship between the outcomes and explanatory variables were assessed using mixed linear models.

Results

There were less > 2nd parity cows in conventional farming. The conventional cows had higher milk yields and received more concentrates than organic cows. Although after adjustment for milk yield and parity, somatic cell count was lower in organic cows than conventional cows. There was a higher proportion of quarters that were dried off at the herd visit in organic herds. No differences in the interval to first AI, interval to last AI or calving interval was revealed between organic and conventional cows. There was no difference between conventional and organic cows in quarter samples positive for mastitis bacteria from the herd visit. Milk yield and parity were associated with the likelihood of at least one quarter positive for mastitis bacteria. There was few S. aureus isolates resistance to penicillin in both management systems. Penicillin resistance against Coagulase negative staphylococci isolated from subclinically infected quarters was 48.5% in conventional herds and 46.5% in organic herds.

Conclusion

There were no large differences between reproductive performance and udder health between conventional and organic farming for Norwegian Red cows.

Milk yield, udder health and reproductive performance in Swedish organic and conventional dairy herds

Organic dairy farming is an expanding segment of the dairy sector where cow management differs from the conventional model in many respects. Thus, a comparative evaluation of disease and welfare status in organically and conventionally managed dairy cows is required. Assessment of milk yield, udder health and reproductive performance (RP) was done in 20 organically and 20 conventionally managed Swedish dairy herds. In accordance with earlier findings we confirmed lower milk yield in organic cows. Udder health and RP were chosen as indicators of animal health in view of their clinical relevance and the availability of appropriate data bases providing good background knowledge for further animal health assessment. No obvious differences were found in the investigations of somatic cell count (SCC) profiles or time to veterinary-treated cases of mastitis between organically and conventional managed cows. Pregnancy success at first insemination, an appropriate measurement of RP with biological interpretation and background, did not reveal any difference between management types, whereas the hazard rate-ratio (HR) of having a calving-interval was significantly lower (HR=0·71) in organically managed cows. The calving-interval is an important financial determinator in dairy production, but it is not considered an optimal indicator of biologic relevance as it partially reflects farmer decisions. In conclusion, the organically managed cows in this study did not differ from conventionally managed cows in udder health or RP, with the exception of calving interval.