Heritability and repeatability of milk lactose and its relationships with traditional milk traits,somatic cell score and freezing point in Holstein cows

Lactose percentage (LP) in milk is currently determined in most herd-testing schemes, and globally, it is usually routinely recorded in the framework of the official milk recording procedures. However, few studies have investigated the phenotypic and genetic variability of this component. Data used in the present paper consisted of 59 811 test-day records from 4355 Holstein cows in 266 herds. Heritabilities of LP and lactose yield (LY) were estimated through single-trait repeatability animal models, whereas genetic and phenotypic correlations of LP and LY with milk composition and production traits, somatic cell score and milk freezing point were estimated using bivariate models. Fixed effects included in the analyses were herd-test-date, season of calving, parity, stage of lactation and the interaction between parity and stage of lactation. Random effects were animal additive genetic, within and across lactation permanent environment and the residual. Lactation curves of LP and LY increased from parturition to the peak of lactation and decreased thereafter, mirroring the typical curve of milk yield. Lactose percentage was greater in first- than later-parity cows. Heritabilities of LP and LY were 0.43±0.03 and 0.14±0.02, respectively, and LP and protein percentage were the most repeatable traits. Genetic correlations (r_a) of LP with somatic cell score, LY and milk freezing point were −0.22±0.08, 0.28±0.08 and −0.46±0.05, respectively. Genetic relationships of LY with milk yield (r_a=0.97±0.00), fat percentage (r_a=−0.71±0.06), protein percentage (r_a=−0.57±0.06) and protein yield (r_a=0.64±0.06) were moderate to strong. Results suggest that milk LP could be considered in breeding strategies to accelerate the gain of correlated low heritable traits. Further research is needed to evaluate the feasibility of including LP in the selection index of Italian Holstein population to address country-specific needs and market demands.     

Rumination and activity levels as predictors of calving for dairy cows

The Australian dairy herd size has doubled over the last 20 years substantially increasing the time that farmers require for individual animal attention to monitor and intervene with events such as calving. Technology will help focus this limited labour resource on individual cows that require assistance. The objective of this experiment was to first determine the profiles of rumination duration and level of activity as determined by sensors between, and within, days around calving and second to use these data to predict the day of calving for pasture-based dairy cows. After 2 weeks from the expected calving date, 27 cows were fitted with SCR HR LD Tags, located in 40×90 m² paddock and offered ad libitum oaten hay and 2 kg grain-based concentrate/cow per day until calving. Hourly activity and rumination data for each cow, as determined by the SCR tags, were fitted with linear mixed models and all parameters were estimated using restricted maximum likelihood. Rumination duration decreased by 33% over the day prior and the day of calving, with the decline in rumination duration starting the day prepartum. Activity levels were maintained prepartum but increased in the days postpartum. The day of calving was recorded and used to determine the gold standard positive (the day before calving) and negative (all other) dates. A threshold rumination level of 0.9 (decline in rumination duration of 10%) gave the optimal combination of 70% sensitivity and 70% specificity. This experiment shows the potential to use rumination duration to predict the day of calving and the opportunity to use sensor data to monitor animal health.     

Genetic parameters for first lactation test-day milk flow in Holstein cows

Genetic parameters for test-day milk flow (TDMF) of 2175 first lactations of Holstein cows were estimated using multiple-trait and repeatability models. The models included the direct additive genetic effect as a random effect and contemporary group (defined as the year and month of test) and age of cow at calving (linear and quadratic effect) as fixed effects. For the repeatability model, in addition to the effects cited, the permanent environmental effect of the animal was also included as a random effect. Variance components were estimated using the restricted maximum likelihood method in single- and multiple-trait and repeatability analyses. The heritability estimates for TDMF ranged from 0.23 (TDMF 6) to 0.32 (TDMF 2 and TDMF 4) in single-trait analysis and from 0.28 (TDMF 7 and TDMF 10) to 0.37 (TDMF 4) in multiple-trait analysis. In general, higher heritabilities were observed at the beginning of lactation until the fourth month. Heritability estimated with the repeatability model was 0.27 and the coefficient of repeatability for first lactation TDMF was 0.66. The genetic correlations were positive and ranged from 0.72 (TDMF 1 and 10) to 0.97 (TDMF 4 and 5). The results indicate that milk flow should respond satisfactorily to selection, promoting rapid genetic gains because the estimated heritabilities were moderate to high. Higher genetic gains might be obtained if selection was performed in the TDMF 4. Both the repeatability model and the multiple-trait model are adequate for the genetic evaluation of animals in terms of milk flow, but the latter provides more accurate estimates of breeding values.     

Effects of stage of pregnancy on variance components,daily milk yields and 305-day milk yield in Holstein cows,as estimated by using a test-day model

Pregnancy and calving are elements indispensable for dairy production, but the daily milk yield of cows decline as pregnancy progresses, especially during the late stages. Therefore, the effect of stage of pregnancy on daily milk yield must be clarified to accurately estimate the breeding values and lifetime productivity of cows. To improve the genetic evaluation model for daily milk yield and determine the effect of the timing of pregnancy on productivity, we used a test-day model to assess the effects of stage of pregnancy on variance component estimates, daily milk yields and 305-day milk yield during the first three lactations of Holstein cows. Data were 10 646 333 test-day records for the first lactation; 8 222 661 records for the second; and 5 513 039 records for the third. The data were analyzed within each lactation by using three single-trait random regression animal models: one model that did not account for the stage of pregnancy effect and two models that did. The effect of stage of pregnancy on test-day milk yield was included in the model by applying a regression on days pregnant or fitting a separate lactation curve for each days open (days from calving to pregnancy) class (eight levels). Stage of pregnancy did not affect the heritability estimates of daily milk yield, although the additive genetic and permanent environmental variances in late lactation were decreased by accounting for the stage of pregnancy effect. The effects of days pregnant on daily milk yield during late lactation were larger in the second and third lactations than in the first lactation. The rates of reduction of the 305-day milk yield of cows that conceived fewer than 90 days after the second or third calving were significantly (P<0.05) greater than that after the first calving. Therefore, we conclude that differences between the negative effects of early pregnancy in the first, compared with later, lactations should be included when determining the optimal number of days open to maximize lifetime productivity in dairy cows.     

Induction of twinning in Holstein and Japanese black cows by ipsilateral frozen embryo transfer

Induction of twinning by ipsilateral nonsurgical transfer of two frozen-thawed Japanese Black bovine embryos to each of 20 Holstein and 26 Japanese Black cows, that had been kept under a stable in private farm conditions, was examined. The cows were monitored every 20 days from Day 25 to Day 65 of gestation for pregnancy and fetus survival (estrus is Day 0). Seventy-five per cent (15 of 20), 65.0% (13 of 20) or 60.0% (12 of 20) and 61.5% (16 of 26), 53.8% (14 of 26) or 50.0% (13 of 26) of Japanese Black cows were diagnosed pregnant at 25, 45 and 65 days after transfer by ultrasonic echography. Embryonic losses were observed between Days 25 and 65 in 29.2% (7) Holstein and 31.8% (7) Japanese Black cows. The twin pregnancy rate in Holstein and Japanese Black cows decreased with time; 60.0% (9 of 15) vs. 37.5% (6 of 16) at Day 25; 53.8% (7 of 13) vs. 28.6% (4 of 14) at Day 45 and 41.7% (5 of 12) vs. 15.4% (2 of 13) at Day 65. At calving, Holstein cows produced five sets of twins and seven single calves, and Japanese Black cows two sets of twins and 11 single calves. The twinning rate in Holstein cows was higher (P < 0.05) than that in Japanese Black cows, 41.7% (5 of 12) vs. 15.4% (2 of 13). The calf birth weight in Holsteins was heavier (P < 0.05) than that in Japanese Black dams (24.5 kg, 33.6 kg vs. 19.3 kg, 25.5 kg for twin and single calves). The placental weight in Holstein dams calving twins was heavier than that in Holstein dams calving a single calf or in Japanese Black dams calving either twins or a single calf (6.6 kg vs. 3.5 kg, 4.6 kg or 2.8 kg). The number of placentome in Holstein dams calving twins was also higher (P < 0.05) than that in Holstein dams calving a single calf or Japanese Black dams (103.5 vs. 41.8, 67.9, 33.0). The number of placentome was approximately double in dams calving twins than that of dams calving a single calf.     

Screening for high fertility in high-producing dairy cows

A retrospective study involving 2756 pregnancies from two commercial dairy herds in northeastern Spain determined relationships between management, production and reproductive data, and high fertility (conception before 90 days in milk) in high-producing dairy cows. High fertility was registered in 989 (35.9%) cows. The following data were recorded for each animal: herd, repeated animal (cows included two or more times within the study in which data were obtained from different lactational periods), parity (primiparous versus multiparous), previous twinning, reproductive disorders following calving (retained placenta, primary metritis) and at postpartum gynecological examination (incomplete uterine involution, pyometra and ovarian cysts), days in milk at conception, previous estrous synchronization and season of calving and conception. In order to evaluate the possible effect of high production during the peak milk yield on subsequent fertility, daily milk production at Day 50 postpartum was also recorded and cows were classified as high (> or = 50 kg) and low (< 50 kg) producers. Logistic regression analysis indicated no significant effects of herd, repeated animal, previous twinning, reproductive disorders such as primary metritis, incomplete uterine involution, pyometra and ovarian cysts, previous estrous synchronization and season of calving and insemination. Based on the odds ratio, the likelihood of high fertility increased in high-producer cows by a factor of 6.8. High fertility was less likely for multiparous cows (by a factor of 0.35) and for cows suffering placenta retention (by a factor of 0.65). High fertile cows produced a mean of 49.5 kg milk at Day 50 postpartum, in contrast to that 43.2 kg milk of the remainder cows. These findings question the negative effect of high production on fertility. Our results indicated that high individual cow milk production can be positively related to high fertility.     

Non-additive genetic effects for fertility traits in Canadian Holstein cattle (Open Access publication )

The effects of additive, dominance, additive by dominance, additive by additive and dominance by dominance genetic effects on age at first service, non-return rates and interval from calving to first service were estimated. Practical considerations of computing additive and dominance relationships using the genomic relationship matrix are discussed. The final strategy utilized several groups of 1000 animals (heifers or cows) in which all animals had a non-zero dominance relationship with at least one other animal in the group. Direct inversion of relationship matrices was possible within the 1000 animal subsets. Estimates of variances were obtained using Bayesian methodology via Gibbs sampling. Estimated non-additive genetic variances were generally as large as or larger than the additive genetic variance in most cases, except for non-return rates and interval from calving to first service for cows. Non-additive genetic effects appear to be of sizeable magnitude for fertility traits and should be included in models intended for estimating additive genetic merit. However, computing additive and dominance relationships for all possible pairs of individuals is very time consuming in populations of more than 200 000 animals.     

An empirical analysis of the cost of rearing dairy heifers from birth to first calving and the time taken to repay these costs

Rearing quality dairy heifers is essential to maintain herds by replacing culled cows. Information on the key factors influencing the cost of rearing under different management systems is, however, limited and many farmers are unaware of their true costs. This study determined the cost of rearing heifers from birth to first calving in Great Britain including the cost of mortality, investigated the main factors influencing these costs across differing farming systems and estimated how long it took heifers to repay the cost of rearing on individual farms. Primary data on heifer management from birth to calving was collected through a survey of 101 dairy farms during 2013. Univariate followed by multivariable linear regression was used to analyse the influence of farm factors and key rearing events on costs. An Excel spreadsheet model was developed to determine the time it took for heifers to repay the rearing cost. The mean±SD ages at weaning, conception and calving were 62±13, 509±60 and 784±60 days. The mean total cost of rearing was £1819±387/heifer with a mean daily cost of £2.31±0.41. This included the opportunity cost of the heifer and the mean cost of mortality, which ranged from £103.49 to £146.19/surviving heifer. The multivariable model predicted an increase in mean cost of rearing of £2.87 for each extra day of age at first calving and a decrease in mean cost of £6.06 for each percentile increase in time spent at grass. The model also predicted a decrease in the mean cost of rearing in autumn and spring calving herds of £273.20 and £288.56, respectively, compared with that in all-year-round calving herds. Farms with herd sizes⩾100 had lower mean costs of between £301.75 and £407.83 compared with farms with <100 milking cows. The mean gross margin per heifer was £441.66±304.56 (range £367.63 to £1120.08), with 11 farms experiencing negative gross margins. Most farms repaid the cost of heifer rearing in the first two lactations (range 1 to 6 lactations) with a mean time from first calving until breaking even of 530±293 days. The results of the economic analysis suggest that management decisions on key reproduction events and grazing policy significantly influence the cost of rearing and the time it takes for heifers to start making a profit for the farm.     

The use of embryo transfer in the field for increased calf crops in beef and dairy cattle

Non-surgical transfer of one embryo to 63 previously synchronized inseminated recipients was performed on farms to induce twinning in beef and dairy cattle. All the transfers were done by technicians of A.I. centers. After calving, a twinning rate of 44.4% was achieved with no differences between beef Charolais heifers (45.4%), lactating Normande cows (42.8%) and dairy Friesian cows (45.4%). Compared with controls, the calving crop after a three-breeding-cycle period was significantly higher with recipients: 1.16 calf per treated recipient vs. 0.83 calf per control animal. It would seem that the possibility of obtaining about one-third more calves with embryo transfer could be of economical interest to increase meat production from cattle herds.     

The effects of polymorphisms in the DGAT1, leptin and growth hormone receptor gene loci on body energy, blood metabolic and reproductive traits of Holstein cows

The objective of this study was to examine the impact of polymorphisms in the acyl-CoA:diacylglycerol acyltransferase ( DGAT1 ), leptin and growth hormone receptor genes on body energy (body condition score, total body energy content and cumulative effective energy balance) and blood metabolic traits (levels of β-hydroxybutyrate, glucose and non-esterified fatty acids), measured once before the first calving and then repeatedly throughout first lactation in 497 Holstein cows. The influence of the same polymorphisms on cow reproductive performance and health during the first and second lactations was also assessed. Several reproductive traits were considered including interval, conception and insemination traits, as well as incidence of metritis and reproductive problems. Genotyping was performed using PCR-RFLP ( DGAT1 , leptin ) or allele-specific PCR ( growth hormone receptor ). For each locus, the effect of allele substitution on body energy and blood metabolic traits was estimated using random regression models. The same effect on reproductive traits was assessed with single-trait mixed linear models. Significant ( P  <   0.05) effects on specific reproductive traits were observed. DGAT1 and growth hormone receptor alleles responsible for significant increases in milk production were found to have an adverse effect on reproduction, while the leptin allele responsible for significant increase in milk production was linked to marginally increased metritis frequency. Furthermore, the three studied loci were also found to significantly ( P  <   0.05) affect certain body energy and blood metabolic traits. Several associations are published for the first time, but these should be confirmed by other investigators before the polymorphisms are used in gene-assisted selection.     

Frequency of twin births among Holstein-Friesian cows in a warm dry climate

The objectives of this study were to examine 1) the effect of parity of dam and season of birth on the incidence of twins in Holstein-Friesian cattle in a warm, dry climate and 2) the sex ratio, gestation period and birth weight of calves born. Natural calvings (n = 24,843) from nine dairy farms in Saudi Arabia were evaluated over an 8-year period. The calendar year was divided into six bimonthly intervals to identify a possible seasonal effect on the number of natural twins born (twinning rate). The twinning rate increased (P < 0.05) from 1.0% (103 10,094 ) at first calving to 8.0% (1,178 14,749 ) for all the subsequent calvings. The twinning rate was similar with the second calving (P(2)) at 7.0% (417 5,929 ), the third calving (P(3)) at 7.5% (218 2,896 ), and the fourth calving (P(4)) at 7.8% (147 1,864 ). Correspondingly, cows having >/= five calves had a higher (P < 0.01) twinning rate at 9.0% (164 1,805 ) than cows with too, three or four calvings collectively at 7.3% (782 10,689 ). The seasonal effect on twinning rate was significant within all parity calvings except in primiparous females. The peak twinning rate occurred in the third season interval (May/June) at 9.3% (66 708 ) with P(2), at 13.0% (34 262 ) with P(3), at 13.8% (27 196 ) with P(4), and at 12.5% (23 184 ) with P(5) females. The male to female ratio was different (P < 0.01) for multiparous females (55:46; n = 12,305). The ratio of males to females (55:45) was also different (P < 0.01) for all twin pairs (n = 1,151), evaluated in the study. The gestation period for cows with single calves was 8.5 days longer (P < 0.05) than that of cows carrying twin calves. The birth weight of single calves was 13.1 kg greater (P < 0.05) than that of twin calves. The reason for the marked increase in the twinning rate during the warmest months may be explained by greater embryo mortality in the hot vs cool months.     

Effect of Feeding on Reproductive Performance in Finnish Dairy Cows

The effect of 2 types of feeding on the involution of the genital tract and on the fertility was studied in 79 Finnish dairy cows on a research farm. The cows were fed twice a day with home-produced feed in accordance with the Finnish feeding standard. The cows were divided according to the type of feed into a hay-urea group and a silage group. The cows were examined clinically by rectal palpation 3 times a week during 8 weeks postpartum. The time required for the complete involution of uterus and cervix was recorded. The cows in the silage group had a significantly longer time in uterine involution, a lower fertility rate at first insemination and a longer interval from calving to conception than those in the hay-urea group. The pregnancy rate in the first insemination was in the hay-urea group 91 % and in the silage group 57 %. The interval between calving and the first insemination was shorter in the hay-urea group than in the silage group; 71.4 ± 10.6 and 74.0 ± 10.3 days, respectively. The interval between calving and conception was in the hay-urea group significantly (p < 0.01) shorter than in the silage group; 74.8 ± 15.1 and 89.5 ± 24.4 days, respectively.     

Supplementation of antioxidant micronutrients reduces stress and improves immune function/response in periparturient dairy cows and their calves

BackgroundPeriparturient period induces stress in cows which fluctuates hormonal and metabolic function and causes immune suppression. Apart from impairing the health, production, and reproduction of cows, it also influences the well-being of newborn calves by decreasing the colostrum quality. Micronutrients are known for optimal health and production and their effects on parturition stress, immune response in both cow and its calf need to be explored.AimThe aim of this study was to see the effect of oral supplementation of micronutrients during the prepartum period on the health status of crossbred dairy cows and subsequently on their newborn calves.MethodsA total of 42 healthy multiparous cows were selected and randomly divided into five groups with seven cows in each group, i.e. control (Basal Diet, BD), VA group (BD + vitamin A, 10⁵ IU), Zn group (BD + zinc sulphate, 60 ppm), VE group (BD + vitamin E, 2500 IU), and combined supplementation (CS) group (BD + combination of VA, Zn, and VE). The supplements were offered in compounded concentrate DM (100 g) to individual cows once daily before the morning feeding and the remaining portion was incorporated in the TMR. Feeding was started one month before the expected days of calving till calving. Blood samples were collected from cows at days -15, -7, -3, 0, +3, +7, and +15 relative to the day of calving. Blood samples from newborn calves and milk samples of cows were collected at days 0, +3, +7, and +15. Milk somatic cell counts (SCC) were estimated using a cell counter. Cortisol was estimated by ELISA kit in blood and milk plasma of cows and in the blood plasma of their calves. Total immunoglobulins (Ig) were estimated in milk of cows and serum of calves using zinc sulphate turbidity method. Blood neutrophils from cows and calves were studied for phagocytic activity (PA) using nitro blue tetrazolium (NBT) assay.Data were analysed by repeated-measures two-way ANOVA using the mixed procedure of SAS, and the pairwise comparison was performed using a multiple comparison test (Tukey).ResultsCombined supplementation of micronutrients decreased (P < 0.05) maternal blood plasma (control vs. CS group, 5.98 ± 0.20 vs. 3.86 ± 0.23 ng/mL) and milk plasma (3.96 ± 0.13 vs. 2.71 ± 0.10 ng/mL) cortisol, milk SCC (3.05 ± 0.11 vs. 2.12 ± 0.10 × 10⁵ cells/mL) and increased (P < 0.05) total milk Ig concentration (18.80 ± 0.11 vs. 23.04 ± 0.57 mg/mL) and the PA of blood neutrophils (0.84 ± 0.03 vs. 1.07 ± 0.03). Similarly, lower blood cortisol concentration (9.69 ± 0.35 vs. 6.02 ± 0.18 ng/mL) and higher (P < 0.05) total Ig (23.26 ± 0.11 vs. 30.34 ± 0.70 mg/mL) and PA of blood neutrophils (0.37 ± 0.02 vs. 0.52 ± 0.02) were observed in the calves born to CS group of cows as compared to the control. Highest (P < 0.05) positive effects (lower stress levels and higher immune response) of treatment were noticed in CS group followed by VE group and then Zn group. However, VA group didn’t differ from the control group.ConclusionOur results indicate that micronutrient interventions during the prepartum period can improve the health status of dairy calves and subsequently the well-being of their calves.     

Multiple-Trait Genomic Selection Methods Increase Genetic Value Prediction Accuracy

Genetic correlations between quantitative traits measured in many breeding programs are pervasive. These correlations indicate that measurements of one trait carry information on other traits. Current single-trait (univariate) genomic selection does not take advantage of this information. Multivariate genomic selection on multiple traits could accomplish this but has been little explored and tested in practical breeding programs. In this study, three multivariate linear models (i.e., GBLUP, BayesA, and BayesCπ) were presented and compared to univariate models using simulated and real quantitative traits controlled by different genetic architectures. We also extended BayesA with fixed hyperparameters to a full hierarchical model that estimated hyperparameters and BayesCπ to impute missing phenotypes. We found that optimal marker-effect variance priors depended on the genetic architecture of the trait so that estimating them was beneficial. We showed that the prediction accuracy for a low-heritability trait could be significantly increased by multivariate genomic selection when a correlated high-heritability trait was available. Further, multiple-trait genomic selection had higher prediction accuracy than single-trait genomic selection when phenotypes are not available on all individuals and traits. Additional factors affecting the performance of multiple-trait genomic selection were explored.     

Genomic analysis of dominance effects on milk production and conformation traits in Fleckvieh cattle

Background

Estimates of dominance variance in dairy cattle based on pedigree data vary considerably across traits and amount to up to 50% of the total genetic variance for conformation traits and up to 43% for milk production traits. Using bovine SNP (single nucleotide polymorphism) genotypes, dominance variance can be estimated both at the marker level and at the animal level using genomic dominance effect relationship matrices. Yield deviations of high-density genotyped Fleckvieh cows were used to assess cross-validation accuracy of genomic predictions with additive and dominance models. The potential use of dominance variance in planned matings was also investigated.

Results

Variance components of nine milk production and conformation traits were estimated with additive and dominance models using yield deviations of 1996 Fleckvieh cows and ranged from 3.3% to 50.5% of the total genetic variance. REML and Gibbs sampling estimates showed good concordance. Although standard errors of estimates of dominance variance were rather large, estimates of dominance variance for milk, fat and protein yields, somatic cell score and milkability were significantly different from 0. Cross-validation accuracy of predicted breeding values was higher with genomic models than with the pedigree model. Inclusion of dominance effects did not increase the accuracy of the predicted breeding and total genetic values. Additive and dominance SNP effects for milk yield and protein yield were estimated with a BLUP (best linear unbiased prediction) model and used to calculate expectations of breeding values and total genetic values for putative offspring. Selection on total genetic value instead of breeding value would result in a larger expected total genetic superiority in progeny, i.e. 14.8% for milk yield and 27.8% for protein yield and reduce the expected additive genetic gain only by 4.5% for milk yield and 2.6% for protein yield.

Conclusions

Estimated dominance variance was substantial for most of the analyzed traits. Due to small dominance effect relationships between cows, predictions of individual dominance deviations were very inaccurate and including dominance in the model did not improve prediction accuracy in the cross-validation study. Exploitation of dominance variance in assortative matings was promising and did not appear to severely compromise additive genetic gain.     

牛FSHR基因第10外显子单核苷酸多态性及其与双胎性状的关系

以秦川牛和荷斯坦奶牛的双胎母牛和单胎母牛为实验材料 ,以牛的FSHR基因的第 10个外显子作为标记牛双胎性状的候选基因 ,用SNP法进行了多态检测 .结果发现 ,在秦川牛的双胎母牛中突变率 6 0 % (6 10 ) ,而在单胎母牛中突变率为 2 0 % (2 10 ) ;在荷斯坦奶牛中 ,双胎母牛突变率为31 2 5 % (5 16 ) ,单胎母牛突变率为 6 6 7% (1 15 ) ;由此可见双胎牛和单胎牛二者之间FSHR基因的第 10个外显子的突变率差异明显 .这表明 ,选择FSHR基因的第 10个外显子有可能作为双胎性状的候选基因 .序列分析发现 ,在FSHR基因的第 15 0 6位碱基发生了突变 (T→C) ,但氨基酸没有发生变化 .     

Effect of hyperketonaemia and feeding on fertility in dairy cows

Fertility in relation to acetone concentration in milk and level of nutrition was studied in 38,624 lactations from 474 herds over a 3-year period. Herd-related data on nutrition were collected once each year. Milk acetone concentrations higher than 0.40 mM were deemed to be hyperketonaemic. The interval from calving to first service was about 5 days longer in cows with acetone concentrations >2.00 mM, while the interval to the last service was shortest at 0.40 to 1.00 mM. The risk for cystic ovaries was severely increased in first calving heifers with acetone concentrations >2.00 mM (odds ratio; 8.7). In herds with a high frequency of hyperketonaemic cows, primiparous cows had a 6-day longer period from calving to the first service and a 12-day longer period from calving to the last service. Increased feeding frequency of concentrate (2 vs 4 times/day) was related to shorter intervals from calving to first service and from calving to last service of 5 and 6 days, respectively, in mature cows. Increased total intake of energy in early lactation was related to shorter intervals from calving to last service in both primiparous and multiparous cows, 0.3 and 0.1 days per megajoule metabolizable energy, respectively. However, increased amounts of concentrate at calving in multiparous cows, and 15 days after calving in primiparous cows, were related to longer intervals from calving to last service and from calving to first service, respectively. The negative effect on these intervals was estimated to be approximately 2 days per kilogram of concentrate.     

Genomic Selection for the Improvement of Antibody Response to Newcastle Disease and Avian Influenza Virus in Chickens

Newcastle disease (ND) and avian influenza (AI) are the most feared diseases in the poultry industry worldwide. They can cause flock mortality up to 100%, resulting in a catastrophic economic loss. This is the first study to investigate the feasibility of genomic selection for antibody response to Newcastle disease virus (Ab-NDV) and antibody response to Avian Influenza virus (Ab-AIV) in chickens. The data were collected from a crossbred population. Breeding values for Ab-NDV and Ab-AIV were estimated using a pedigree-based best linear unbiased prediction model (BLUP) and a genomic best linear unbiased prediction model (GBLUP). Single-trait and multiple-trait analyses were implemented. According to the analysis using the pedigree-based model, the heritability for Ab-NDV estimated from the single-trait and multiple-trait models was 0.478 and 0.487, respectively. The heritability for Ab-AIV estimated from the two models was 0.301 and 0.291, respectively. The estimated genetic correlation between the two traits was 0.438. A four-fold cross-validation was used to assess the accuracy of the estimated breeding values (EBV) in the two validation scenarios. In the family sample scenario each half-sib family is randomly allocated to one of four subsets and in the random sample scenario the individuals are randomly divided into four subsets. In the family sample scenario, compared with the pedigree-based model, the accuracy of the genomic prediction increased from 0.086 to 0.237 for Ab-NDV and from 0.080 to 0.347 for Ab-AIV. In the random sample scenario, the accuracy was improved from 0.389 to 0.427 for Ab-NDV and from 0.281 to 0.367 for Ab-AIV. The multiple-trait GBLUP model led to a slightly higher accuracy of genomic prediction for both traits. These results indicate that genomic selection for antibody response to ND and AI in chickens is promising.     

Postpartum fertility in beef cattle producing twins

Postpartum fertility was measured in 42 plur iparous Hereford cows and first calf Hereford heifers that calved after embryo transfer to induce twins. Dams were exposed to a Hereford bull from 4: 00 P.M. to 8:00 A.M. each day from 60 days postpartum until pregnancy was confirmed or calves were weaned at 180 days of age. Days open ($\text{X}\text{± SE}$) for dams that produced single and twin calves were 84.1 ± 4.6 (n = 12) and 94.9 ± 6.2 (n = 30), respectively. Corresponding values for dams that nursed one calf, including six females that lost one calf of a twin set at birth, and dams that nursed twins were 89.3 ± 6.4 (n = 18) and 93.4 ± 8.5 (n = 24). No significant differences were observed due to calving or suckling twin calves. Heifers that calved twins had a shorter mean interval to conception than cows that calved twins. These results are interpreted to mean that with proper management during the prepartum and postpartum periods, reduced fertility in beef cattle that produce twins need not occur.