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Berry D.P.,Teagasc | McCarthy J.,Irish Cattle Breeding Federation
Applied Animal Behaviour Science | Year: 2012

The ability to rapidly identify temporal deviations of an animal from its norm will be important in the management of individual cows in large herds. Furthermore, predictors of genetic merit for especially health traits are useful to augment the accuracy of selection, and thus genetic gain, in breeding programs. The objective of this study was to estimate the repeatability of milking order and to quantify the contribution of differences in additive genetic variation to phenotypic differences (i.e., heritability). The data used in this study included 9813 herd milk recording test-day records with time of milking from 85,532 cows in 1143 herds across an 8-year period. Milking order was available for both morning and evening milking for each cow with, on average, 3.33 milk test-day records (i.e., 6.66 milking events) per lactation, and on average 1.62 lactations per cow. Variance components for milking order were estimated using animal linear mixed models; covariance components between milking order and milk yield, milk composition and somatic cell score (i.e., logarithm 10 somatic cell count) were estimated also using animal linear mixed models. The heritability of milking order was 0.20 indicating partial genetic control of milking order. The repeatability of milking order within test-day, within lactation, and across lactations was 0.63, 0.51, and 0.47, respectively. Milking order was positively (P<0.001), but weakly, phenotypically correlated with milk yield (r=0.04), and milk fat concentration (r=0.01) and negatively (P<0.001), but weakly, correlated with milk protein concentration (r=-0.02) and somatic cell score (r=-0.05). Milking order was positively (P<0.05), although weakly, genetically correlated with milk yield (r=0.07) and negatively (P<0.05), but also weakly, genetically correlated with somatic cell score (r=-0.08). This study is the first to show a contribution of additive genetics to milking order in dairy cattle but the genetic correlation between milking order and somatic cell score was weak. © 2011 Elsevier B.V. Source

Berry D.P.,Teagasc | Crowley J.J.,Irish Cattle Breeding Federation
Journal of Animal Science | Year: 2012

Interest in improving feed efficiency in cattle is intensifying. Residual feed intake (RFI), which is the difference between expected intake and that predicted based on energy demands, is now the most commonly used measure of feed efficiency over a given time period. However, RFI, as commonly defined, is independent of growth rate, which may affect its acceptance by industry. Residual BW gain (RG) has also been proposed as a measure of feed efficiency and is represented as the residuals from a multiple regression model regressing ADG on both DMI and BW. In this study, we propose a new trait, residual intake and BW gain (RIG), which retains the favorable characteristic of both RFI and RG being independent of BW, but animals superior for RIG have, on average, both greater ADG and reduced DMI. Phenotypic and genetic analyses were undertaken on up to 2,605 purebred performance-tested bulls. Clear phenotypic differences in DMI and ADG existed between animals divergent for RIG. The heritability of RIG was 0.36 ± 0.06, which is consistent with the heritability estimates of RFI and other feed efficiency traits measured in the study. The RIG trait was both phenotypically and genetically negatively correlated with DMI and positively correlated with ADG; no correlation existed between RIG and BW. The advantages of both reduced daily DMI and greater ADG in animals superior for RIG are demonstrated compared with animals superior for either RFI or RG. © 2012 American Society of Animal Science. Source

McCarthy J.,Irish Cattle Breeding Federation | Veerkamp R.F.,Animal science Group
Journal of Dairy Science | Year: 2012

Variance components for test-day milk yield were estimated for primiparous animals in a seasonal calving system where 80% of calvings occur within a 5-mo period in the spring. The objective was to investigate if the variance components of milk production were affected by seasonality via month in milk and test month (TM). These effects were, therefore, fitted for both the permanent environment effect and additive genetic effect. Estimates of heritability (0.14-0.27) were found to be lowest during early and late lactation for all calving months. The peak in heritability (0.22-0.27) occurred later in lactation for animals that calved toward the end of the spring calving season. Genetic variance of test day milk yield for all calving months was found to be highest at the beginning of the lactation (2.23-3.36kg2), with a plateau toward the middle of the lactation. Genetic variance was found to be highest (2.98-3.36kg2) for animals calving early in the season. Genetic correlations between corresponding stages of lactation were strongest (0.99-1.00) between consecutive calving months. Genetic correlations were slightly weaker when intervals between calving months increased; however, they remained above 0.96 in all cases. Akaike's information criterion values from models both inclusive and exclusive of TM, suggest that the model exclusive of TM is the preferred model. Estimated breeding values of lactation milk yield from bulls with 20 or more daughters, predicted for a full 305-d lactation, were used to compare the model with the standard test-day model (i.e., exclusive of TM), based on DIM. Correlations were higher than 0.995 for milk yield (and higher than 0.930 for persistency) between models inclusive and exclusive of TM, suggesting that given the straightforward approach taken in the current study, an apparent benefit for including seasonality in the evaluation of test-day milk yield was not found; however, there may be benefits of including it in the estimation of persistency. © 2012 American Dairy Science Association. Source

Berry D.P.,Moorepark Dairy Production Research Center | Kearney J.F.,Irish Cattle Breeding Federation | Roche J.R.,DairyNZ Ltd.
Theriogenology | Year: 2011

There is a paucity of estimates of genetic variation for secondary sex ratio (i.e., sex ratio at birth) in dairy cattle. The objective of this study was to estimate the direct and maternal genetic variance as well as maternal permanent environmental variance for offspring sex in dairy herds. The data consisted of 77,508 births from 61,963 dams and 2,859 sires in 1,369 Irish dairy herds across the years 2003 to 2008, inclusive. Mixed models were used to estimate all parameters. Significant genetic variation in sex ratio existed, with a heritability for secondary sex ratio estimated at 0.02; the genetic standard deviation was 0.07 percentage units. No maternal genetic effects on secondary sex ratio were identified but the proportion of phenotypic variance in secondary sex ratio attributable to maternal permanent environmental effects was similar to that attributable to the additive genetic variance (i.e., 0.02). These results, therefore, suggest that the paternal (genetic) influence on secondary sex ratio is just as large as the maternal (non-genetic) influence, both of which are biologically substantial. The results from this study will be useful in generating a sample population of divergent animals for inclusion in a controlled experiment to elucidate the physiological mechanism underpinning differences in secondary sex ratio. © 2011 Elsevier Inc. Source

Finlay E.K.,Trinity College Dublin | Berry D.P.,Teagasc | Wickham B.,Irish Cattle Breeding Federation | Gormley E.P.,University College Dublin | Bradley D.G.,Trinity College Dublin
PLoS ONE | Year: 2012

Background: Bovine tuberculosis is a significant veterinary and financial problem in many parts of the world. Although many factors influence infection and progression of the disease, there is a host genetic component and dissection of this may enlighten on the wider biology of host response to tuberculosis. However, a binary phenotype of presence/absence of infection presents a noisy signal for genomewide association study. Methodology/Principal Findings: We calculated a composite phenotype of genetic merit for TB susceptibility based on disease incidence in daughters of elite sires used for artificial insemination in the Irish dairy herd. This robust measure was compared with 44,426 SNP genotypes in the most informative 307 subjects in a genome wide association analysis. Three SNPs in a 65 kb genomic region on BTA 22 were associated (i.e. p<10 -5, peaking at position 59588069, p = 4.02×10 -6) with tuberculosis susceptibility. Conclusions/Significance: A genomic region on BTA 22 was suggestively associated with tuberculosis susceptibility; it contains the taurine transporter gene SLC6A6, or TauT, which is known to function in the immune system but has not previously been investigated for its role in tuberculosis infection. © 2012 Finlay et al. Source

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