Genetic Parameters of Foot and Leg Traits in Future AI Bulls: I. Influence of Age at Recording and Classifier

Information on foot and leg traits was collected on 8494 young potential future AI bulls of the three populations Danish Red, Danish Friesian and Danish Jersey by two classifiers between 1985 and 1996. Each animal was assessed at 5 and 10 months of age. The data set was used to examine the influence of age and classifier on genetic parameters of foot and leg traits by treating traits recorded at two different times or by two different people as a different characteristic in a bivariate analysis. The general incidence of foot and leg diseases was very low in young animals: only interdigital dermatitis, heel necrosis and solar bruising showed a frequency higher than 2% in 10-month-old bulls. The same traits measured on different claws yielded very high genetic correlations (r_g 0.77-0.98), suggesting that the number of measurements could be reduced. Hooves increased in size with age, and the genetic correlation between the two age classes was high (r_g 0.60-0.77). The agreement between classifiers was very high for objectively measured traits, especially for the younger age class, and interdigital dermatitis and heel necrosis, but inconclusive for the subjectively scored characteristics.     

A multiple-phenotype imputation procedure as a method for prediction of cheese-making efficiency in Spanish Assaf sheep

Sheep milk is mainly intended to manufacture a wide variety of high-quality cheeses. The ovine cheese industry would benefit from an improvement, through genetic selection, of traits related to the milk coagulation properties (MCPs) and cheese yield-related traits, broadly denoted as “cheese-making traits.” Considering that routine measurements of these traits needed for genetic selection are expensive and time-consuming, this study aimed to evaluate the accuracy of a cheese-making phenotype imputation method based on the information from official milk control records combined with the pH of the milk. For this study, we analyzed records of milk production traits, milk composition traits, and measurements of cheese-making traits available from a total of 1,145 dairy ewes of the Spanish Assaf sheep breed. Cheese-making traits included five related to the MCPs and two cheese yield-related traits. The milk and cheese-making phenotypes were adjusted for significant effects based on a general linear model. The adjusted phenotypes were used to define a multiple-phenotype imputation procedure for the cheese-making traits based on multivariate normality and Markov chain Monte Carlo sampling. Five of the seven cheese-making traits considered in this study achieved a prediction accuracy of 0.60 computed as the correlation between the adjusted phenotypes and the imputed phenotypes. Particularly the logarithm of curd-firming time since rennet addition (logK₂₀) (0.68), which has been previously suggested as a potential candidate trait to improve the cheese ability in this breed, and the logarithm of the ratio between the rennet clotting time and the curd firmness at 60 min (logRCT/A60) (0.65), which has been defined by other studies as an indicator trait of milk coagulation efficiency. This study represents a first step toward the possible use of the phenotype imputation of cheese-making traits to develop a practical methodology for the dairy sheep industry to impute cheese-making traits only based on the analysis of a milk sample without the need of pedigree information. This information could be also used in future planning of specific breeding programs considering the importance of the cheese-making efficiency in dairy sheep and highlights the potential of phenotype imputation to leverage sample size on expensive, hard-to-measure phenotypes.     

Mycoplasmosis: Demonstration of Pathogenicity of a Danish Strain of Mycoplasma

During the fall of 1966 several strains of Mycoplasma were isolated from semen samples of bulls. A strain “K” isolated from a bull with simultaneous occurrence of leucocytes and mycoplasmas in the semen was selected for a series of experiments; the mammary gland was chosen as pilot organ.     

The sensitivity of predicted financial and genetic gains in Holsteins to changes in the economic value of traits

The objective of this study was to assess the impact of using different relative economic values (REVs) in selection indices on predicted financial and trait gains from selection of sires of cows and on the choice of leading Holstein bulls available in the UK dairy industry. Breeding objective traits were milk yield, fat yield, protein yield, lifespan, mastitis, non‐return rate, calving interval and lameness. Relative importance of a trait, as estimated by a.h², was only moderately related to the rate of financial loss or total economic merit (ΔTEM) per percentage under‐ or overestimation of REV (r = 0.38 and 0.29, respectively) as a result of the variance–covariance structure of traits. The effects on TEM of under‐ or overestimating trait REVs were non‐symmetrical. TEM was most sensitive to incorrect REVs for protein, fat, milk and lifespan and least sensitive to incorrect calving interval, lameness, non‐return and mastitis REVs. A guide to deciding which dairy traits require the most rigorous analysis in the calculation of their REVs is given. Varying the REVs within a fairly wide range resulted in different bulls being selected by index and their differing predicted transmitting abilities would result in the herds moving in different directions in the long term (20 years). It is suggested that customized indices, where the farmer creates rankings of bulls tailored to their specific farm circumstances, can be worthwhile.     

Additive genetic relationships between heifer pregnancy and scrotal circumference in Nellore cattle

To estimate heritability (h2) for yearling heifer pregnancy and to estimate the genetic correlation between heifer pregnancy and scrotal circumference, 18,145 records of Nellore heifers exposed to breeding at an age of approximately 14 mo and 25,466 records of contemporary young bulls were analyzed. Heifer pregnancy was considered as a categorical trait, with the value 1 (success) assigned to heifers that were pregnant after rectal palpation approximately 60 d after the end of a 90-d breeding season and the value 0 (failure) otherwise. A single-trait animal model for heifer pregnancy and a two-trait animal model including heifer pregnancy and scrotal circumference were used. Contemporary groups were defined in two ways: including (CG2) or not including (CG1) weaning management of the heifer. Heritability estimates obtained by Method R in single-trait analyses were 0.68 +/- 0.09 and 0.61 +/- 0.10 using CG1 and CG2 definitions, respectively. Heritability estimates for two-trait analyses were 0.69 +/- 0.09 (CG1) and 0.63 +/- 0.08 (CG2) for heifer pregnancy and 0.57 +/- 0.03 (both CG) for scrotal circumference. The genetic correlation estimates between the two traits were 0.20 +/- 0.12 (CG1) and 0.20 +/- 0.13 (CG2). Based on the results of this study, EPD for heifer pregnancy can be used to select bulls for the production of precocious daughters and will be more effective than selecting on scrotal circumference EPD in Nellore cattle. However, scrotal circumference can be incorporated in a two-trait analysis to increase the accuracy of prediction for heifer pregnancy EPD for young bulls. Using contemporary group without heifer weaning management gave higher h2 and, for two-trait analysis, converged more quickly.     

Genomic and single-step evaluations of carcass traits of young bulls in dual-purpose cattle

Genetic evaluations for carcass traits of young bulls in Normande and Montbeliarde breeds are currently being developed in France. In order to determine a suitable genomic evaluation for three carcass traits of young bulls, genomic breeding values were estimated for young candidates to selection using different approaches. Records of 111,789 Normande and 118,183 Montbeliarde were used. Average progeny pre-adjusted performances (DYD) were calculated for sires. Evaluation approaches were compared based on an assessment of their accuracy (correlation between DYD and estimated breeding values [EBVs]) and bias (regression coefficient of DYD on EBVs) on the 20% youngest AI sires. All genomic approaches were generally more accurate than BLUP (+.045 to +.116 correlation points), except for age at slaughter where single-step GBLUP (SSGBLUP) was the only genomic method leading to a greater accuracy (+.038 to +.126 points). The best setting of the SSGBLUP relationship matrix was characterized by a weight of 30% for pedigree information in the genomic relationship matrix. SSGBLUP was the most valuable evaluation approach for the evaluation of carcass traits of Normande and Montbeliarde young bulls.     

Testicular traits as selection criteria for young Nellore bulls

The objective of this study was to evaluate the possible use of biometric testicular traits as selection criteria for young Nellore bulls using Bayesian inference to estimate heritability coefficients and genetic correlations. Multitrait analysis was performed including 17,211 records of scrotal circumference obtained during andrological assessment (SCAND) and 15,313 records of testicular volume and shape. In addition, 50,809 records of scrotal circumference at 18 mo (SC18), used as an anchor trait, were analyzed. The (co)variance components and breeding values were estimated by Gibbs sampling using the Gibbs2F90 program under an animal model that included contemporary groups as fixed effects, age of the animal as a linear covariate, and direct additive genetic effects as random effects. Heritabilities of 0.42, 0.43, 0.31, 0.20, 0.04, 0.16, 0.15, and 0.10 were obtained for SC18, SCAND, testicular volume, testicular shape, minor defects, major defects, total defects, and satisfactory andrological evaluation, respectively. The genetic correlations between SC18 and the other traits were 0.84 (SCAND), 0.75 (testicular shape), 0.44 (testicular volume), -0.23 (minor defects), -0.16 (major defects), -0.24 (total defects), and 0.56 (satisfactory andrological evaluation). Genetic correlations of 0.94 and 0.52 were obtained between SCAND and testicular volume and shape, respectively, and of 0.52 between testicular volume and testicular shape. In addition to favorable genetic parameter estimates, SC18 was found to be the most advantageous testicular trait due to its easy measurement before andrological assessment of the animals, even though the utilization of biometric testicular traits as selection criteria was also found to be possible. In conclusion, SC18 and biometric testicular traits can be adopted as a selection criterion to improve the fertility of young Nellore bulls.     

Seriousness and stability of subclinical mastitis assessed by quarter milk serum albumin

Bovine Serum Albumin (BSA) concentration in quarter milk samples from 51 cows examined twice, at 1½ months intervals, was related to subclinical mastitis diagnoses and to the change in diagnoses from the first to the second examination. The BSA-concentration increased with increasing scores of the California Mastitis Test (CMT). The concentration of BSA was higher if bacteria were isolated as compared to negative bacteriological findings, and it was higher if “major pathogens” (MaP) (Staphylococcus aureus or Streptococcus dysgalactiae) rather than “minor pathogens” (MiP) (S. epidermidis or α-streptococci) were isolated. There was no interaction in the “effects” of CMT-score and bacteria on BSA-concentration. Quarters which were healthy and pathogenfree at first examination and had a non-specific mastitis at the subsequent examination, had significantly higher BSA-concentration at first examination than those which remained healthy. Quarters with non-specific mastitis at the first examination and infectious mastitis at the next examination had higher BSA-concentration at the first examinition than those which turned out with other diagnoses. Quarters with infectious mastitis and MaP at first examination which had a latent infection at the next testing, had a lower BSA-concentration than those with other second examination diagnosis. In general, BSA seems to be a more sensitive parameter than CMT for showing the early establishment of an inflammatory reaction in the alveolar tissue.     

影响中国西门塔尔牛繁殖性状的环境因素分析

本文利用5个国家级种畜场和8个家畜冷冻精液中心站1979～1998年间的338头西门塔尔公牛的1275头女儿与其所配母牛的繁殖性状资料和重要的生产性状记录,以及有一定数量后裔的61头公牛的915条精子形态性状测定记录,对西门塔尔母牛的配妊时间、产犊间隔、305d产奶量,和公牛的精子形态性状(头长、最大头宽、中段长、主段长、总长)、精子解冻后活力、密度等共计15个性状进行了遗传统计分析。结果表明:场、年度(配种年度、分娩年度、制精年度)、季节(配种季节、分娩季节、采精季节)、与配公牛、胎次等环境因素对母牛主要繁殖性状影响非常显著,而对公牛精子形态性状的影响小于遗传因素。公牛精子形态性状在个体间差异极显著(P<0.01),这种差异代表了真正的遗传差异。     

免疫大师公牛女儿的疾病抗性分析

为探究通过抗病选育的免疫大师公牛女儿的疾病抗性情况,试验收集上海地区3个同时使用免疫大师公牛和普通公牛冻精牧场的5 112条个体疾病记录,采用Logistic回归法分析了犊牛出生季节、成母牛年龄、父亲类型（免疫大师和普通公牛）对部分常见奶牛疾病发病风险的影响。结果表明,出生季节和年龄分别对犊牛和成母牛各类疾病的发病风险有显著影响（P<0.05）;父亲类型对乳房炎的发病风险在部分群体中有显著影响（P<0.05）。与普通公牛的女儿相比,免疫大师公牛女儿乳房炎发病风险更低。综合本研究结果,免疫大师公牛的抗病能力选育技术有效,其在中国奶牛群体的后代表现出更好的疾病抗性,尤其是提高了奶牛乳房炎抗性,为利用育种手段提高奶牛群体的抗病能力和养殖效益提供了可行的技术路线。     

Genetic Correlations Between Beef Traits Measured on Young Performance Test Bulls and Daughter Milk Yield

In a breeding programme where young potential breeding bulls are reared on performance test stations, selection based on own results can be carried out before test inseminations. Both beef and milk production traits are included in the total merit index used for selection, and estimates of genetic and phenotypic parameters of these traits are therefore of interest for an optimal construction of such indices. Data on first lactation milk records from the field and beef records of potential dairy breeding bulls from the Danish performance test stations were analysed in bivariate animal-sire models using the AI-REML algorithm. Genetic correlations of 0.16, 0.25 and 0.43 between feed intake capacity and protein yield were obtained for Red Danish (RD), Danish Black and White (DBW) and Danish Jersey (DJ), respectively. These correlations were significantly different from zero for the two populations (DBW and DJ). Genetic correlations around zero between feed efficiency and protein yield were obtained for all three populations. Genetic correlations of 0.44, 0.19 and 0.47 between average daily gain and protein yield were obtained for RD, DBW and DJ, respectively. The genetic correlations between protein yield and muscle area was close to zero for DBW, while it was -0.31 for RD. Selection index calculations indicate that indices composed of different beef performance traits can be used as early predictors for milk yield. Selection on such an index could increase the breeding value of the young bulls for milk production traits by 0.8-2.0% of the population mean.     

Mycoplasmosis: experimental inoculation of calves with a Danish strain of Mycoplasma bovigenitalium

During the fall of 1966 several strains of Mycoplasma were isolated from semen samples of bulls. A strain, “K”, isolated from a bull with vesiculitis was selected for a series of experiments and proved to be pathogenic for the mammary gland of cows and for the genital tract of bulls (Ernø 1967, Blom & Εrnø 1967). The “K” strain has now been examined serologically by the author, and it must be considered as belonging to the species M. bovigenitalium as determined by complement fixation and indirect haemagglutination tests. This communication reports the results of experimental inoculation of calves.     

Antibody Production in Milk Serum After Virus Instillation of Goat Mammary Gland VI. “Sham Infection” with Special Reference to Rabies

The ERA strain of rabies vaccine virus failed to propagate or cause clinical manifestations when instilled into the mammary gland of lactating goats. However, the virus did produce neutralizing antibodies in this gland as a result of repetitive viral stimulation, a “sham infection”. The protective property of the concentrated and partly purified milk serum antibody was assessed in mice. In the first trial, protective activity was observed when a single dose of milk serum antibody was administered at intervals up to three days after exposure to virulent rabies virus. In the second trial, using a more concentrated milk serum antibody, about half of the mice were protected when the milk serum was administered up to ten days after exposure to virulent virus.     

Evaluation of serum insulin-like growth factor binding proteins (IGFBP) in Angus cattle divergently selected for serum IGF-I concentration

Postweaning serum insulin-like growth factor-I (IGF-I) concentrations and serum IGF binding proteins (IGFBP) were investigated in 68 (1992 Fall-born) and 84 (1999 Fall-born) Angus cattle selected for either high or low serum IGF-I concentrations since 1989. Relative serum levels of IGFBP were determined by [¹²⁵I]IGF-I Western ligand blotting. IGFBP species of 38–42, 34, 30, and 24 kDa were identified. The 34 kDa species was identified as IGFBP-2 by immunoblot analysis. No significant line effects were observed for any of the IGFBP. In both 1992 and 1999, heifers had higher IGFBP-2 levels than bulls (P<0.0005). In 1992 calves, relative levels of the 38–42 and 24 kDa species were significantly correlated with serum IGF-I concentration. In 1999 calves, none of the IGFBP were correlated with serum IGF-I, although IGFBP-2 was negatively correlated with several measures of body weight. No significant line effects were observed for growth or serum IGF-I traits in 1992 calves. However, 1999 high line calves had higher serum IGF-I concentrations and body weights than low line calves (P<0.05). In both 1992 and 1999 calves, bulls had higher serum IGF-I concentrations and body weights than heifers (P<0.05). Thus, while selection for high versus low serum IGF-I concentrations has resulted in divergence between the selection lines and also in changes in body weights, it has not resulted in changes in serum IGFBP levels. Furthermore, circulating IGFBP-2 appears to be higher in heifers than in bulls, and also appears to be negatively correlated with body weights.     

Responses to Selection against Clinical Mastitis in the Norwegian Cattle Population

The genetic trend for clinical mastitis was estimated for Norwegian Cattle, a population in which mastitis resistance has been included in the breeding programme since 1978. More than 1.2 million first-lactation daughters, with clinical mastitis records registered from 1978 to 1995, bred by 2043 sires, were analysed with a linear sire model. For bulls born from 1974 to 1990 a flat genetic trend for clinical mastitis was found. However, bull sires born from 1983 onwards, selected on a breeding goal with increased weight on mastitis relative to milk production, showed consistently larger and favourable selection differentials for mastitis relative to bull sires born earlier, which had an average selection differential of approximately zero. This will influence genetic trend in the population through their sons, which were born from 1990 onwards.     

Responses to Selection against Clinical Mastitis in the Norwegian Cattle Population

The genetic trend for clinical mastitis was estimated for Norwegian Cattle, a population in which mastitis resistance has been included in the breeding programme since 1978. More than 1.2 million first-lactation daughters, with clinical mastitis records registered from 1978 to 1995, bred by 2043 sires, were analysed with a linear sire model. For bulls born from 1974 to 1990 a flat genetic trend for clinical mastitis was found. However, bull sires born from 1983 onwards, selected on a breeding goal with increased weight on mastitis relative to milk production, showed consistently larger and favourable selection differentials for mastitis relative to bull sires born earlier, which had an average selection differential of approximately zero. This will influence genetic trend in the population through their sons, which were born from 1990 onwards.     

中国荷斯坦公牛CN和DUMPS遗传缺陷检测及系谱分析

旨在研究中国荷斯坦牛中瓜氨酸血症(Citrullinemia,CN)和尿苷酸核酶缺乏症(Deficiency of uridinemonophosphate synthase,DUMPS)2种遗传缺陷的携带者比率及系谱来源,并构建更简便的检测方法。本研究通过PCR-RFLP方法对参加我国联合青年公牛后裔测定和良种补贴项目的591头荷斯坦公牛进行了大规模CN和DUMPS的遗传缺陷检测,并构建了奶牛CN隐性有害基因的AS-PCR检测技术。结果,共发现2头CN和1头DUMPS隐性有害基因携带者公牛,携带者比例分别为0.34%和0.17%。经过系谱追溯,2头CN携带者公牛均为澳大利亚公牛Linmack Kriss King-CN后代,DUMPS携带者公牛为美国公牛Skokie sensation Ned后代。基于此,我国有必要尽快建立荷斯坦牛隐性遗传缺陷监控体系并进行系谱标注,通过青年公牛预选和选种选配,避免携带者公牛进入后裔测定和良种补贴项目,以逐步降低我国奶牛群体中隐性有害等位基因频率。     

Genetic evaluation of somatic cell score in dairy cattle considering first and later lactations as two different but correlated traits

A test‐day (TD) random regression model (RRM) was described for the genetic evaluation of somatic cell score (SCS) where first and later lactations were considered as two different but correlated traits. A two‐step covariance function procedure was used to estimate variance–covariances and associated genetic parameters. Analysis of estimated breeding values (EBV), ranking of top bulls and cows and some computational aspects were used to compare RRM with TD repeatability model (RPM) and lactation average model (LAM). Residuals were analysed to assess the relative fit of TD models. Comparison between RRM and RPM showed that RRM has lower mean squared error and gave better fit to the data. For young bulls and cows, the standard deviation (SD) of EBVs was highest for RRM and lowest for LAM implying efficient utilization of information on SCS, in terms of revealing more genetic variation. A much lower correlation of EBVs ranging from 0.80 to 0.92 and significant re‐ranking of top bulls and cows were observed between RRM and LAM. The lower across‐lactation correlation between RRM and LAM indicated that LAM is directed to give more weight to first lactation breeding values. The RRM, where SCS in the first and later lactations was considered as two different but correlated traits was able to make effective use of available information on young bulls and cows, and could offer an opportunity to breeders to utilize EBVs for first and later lactations.     

The use of Markov chain Monte Carlo for analysis of correlated binary data: patterns of somatic cells in milk and the risk of clinical mastitis in dairy cows

Two analytical approaches were used to investigate the relationship between somatic cell concentrations in monthly quarter milk samples and subsequent, naturally occurring clinical mastitis in three dairy herds. Firstly, cows with clinical mastitis were selected and a conventional matched analysis was used to compare affected and unaffected quarters of the same cow. The second analysis included all cows, and in order to overcome potential bias associated with the correlation structure, a hierarchical Bayesian generalised linear mixed model was specified. A Markov chain Monte Carlo (MCMC) approach, that is Gibbs sampling, was used to estimate parameters.

The results of both the matched analysis and the hierarchical modelling suggested that quarters with a somatic cell count (SCC) in the range 41,000–100,000 cells/ml had a lower risk of clinical mastitis during the next month than quarters <41,000 cell/ml. Quarters with an SCC >200,000 cells/ml were at the greatest risk of clinical mastitis in the next month. There was a reduced risk of clinical mastitis between 1 and 2 months later in quarters with an SCC of 81,000–150,000 cells/ml compared with quarters below this level. The hierarchical modelling analysis identified a further reduced risk of clinical mastitis between 2 and 3 months later in quarters with an SCC 61,000–150,000 cells/ml, compared to other quarters.

We conclude that low concentrations of somatic cells in milk are associated with increased risk of clinical mastitis, and that high concentrations are indicative of pre-existing immunological mobilisation against infection. The variation in risk between quarters of affected cows suggests that local quarter immunological events, rather than solely whole cow factors, have an important influence on the risk of clinical mastitis. MCMC proved a useful tool for estimating parameters in a hierarchical Bernoulli model. Model construction and an approach to assessing goodness of model fit are described.