Time filter

Source Type

Lethbridge, Canada

MacNeil M.D.,Delta G | MacNeil M.D.,University of the Free State | Kemp R.A.,RAK Genetic Consulting Ltd
Canadian Journal of Animal Science

MacNeil, M. D. and Kemp, R. A. 2015. Genetic parameter estimation and evaluation of Duroc boars for feed efficiency and component traits. Can. J. Anim. Sci. 95: 155-159. The objective of this research was to produce a genetic evaluation for traits related to feed efficiency of Duroc boars. Meeting this objective required partitioning phenotypic (co)variance into additive genetic and environmental components for feed intake and traits indicative of growth and body composition. Boars (N=3291) were housed in group pens of 22 to 24 animals with two electronic feeders per pen and feed intake was recorded for 8 to 14 wk. Body weight was recorded for each boar at the start and end of test, at approximately 100 kg and at up to three times during the test. The pedigree used contained sire and dam of each boar with at least one recorded phenotype (N=4651) and their maternal and paternal grandsires. Variance components were estimated by restricted maximum likelihood for animal models in a series of uni-variate and bi-variate analyses. Two multiple trait genetic evaluations were conducted to predict estimated breeding value for feed intake using animal models. The first evaluation included feed intake (h2=0.33±0.05), age at 100 kg (h2=0.31±0.04), and subcutaneous fat depth (h2=0.47±0.05). The second genetic evaluation included feed intake, average daily gain (h2=0.27±0.04), mid-test weight (h2=0.33±0.05), and subcutaneous fat depth. Genetic correlations of feed intake with age at 100 kg and fat depth were -0.80±0.05 and  0.57±0.08, respectively. Estimated breeding values for measures of feed efficiency (residual feed intake and residual gain) were calculated from the results of the second analysis and the associated additive genetic (co)variance components. Source

Jamrozik J.,University of Guelph | McGrath S.,RAK Genetic Consulting Ltd | Kemp R.A.,RAK Genetic Consulting Ltd | Miller S.P.,University of Guelph
Journal of Animal Science

Stayability to consecutive calvings was selected as a measure of cow longevity in the Canadian Simmental population. Calving performance data on 188,579 cows and culling information from the Total Herd Reporting System were used to determine whether a cow stayed in a herd for her second and later (up to the eighth) calvings, given that she had calved as 2 yr old. Binary records (n = 1,164,319) were analyzed with animal linear and threshold models including fixed effects of year of birth by season of birth by parity number and age of cow at first calving by parity number and random effects of contemporary group (CG) defined as herd of birth within year by season, animal additive genetic effect, and a cow permanent environmental (PE) effect. All random effects were Legendre polynomial regressions of the same order, defined on the scale from second to the eighth calving. Bayesian methods with Gibbs sampling were used to estimate covariance components and genetic parameters for random effects of models and selected variables on the longitudinal scale. Bayes factors and analyses of mean squared error and correlation between observed and predicted observations indicated that the linear model with regressions of order 3 was most plausible for generating the current data compared with a fixed regression and other random regression (both linear and threshold) models of order up to 4. Estimates of variances for all random effects from the best fitting model changed with the calving number. Estimates of heritability decreased in time: from 0.35 (SD = 0.006) for stayability to second calving to 0.13 (SD = 0.004) for stayability to the eighth calving. Variance due to PE effect constituted the largest part of the total variance of stayability for all longitudinal points followed by genetic and CG components. Genetic effects of stayability to different calvings were relatively highly correlated, from 0.62 (SD = 0.011) to 0.99 (SD = 0.001), and correlation decreased with the time span between calvings. Correlations for PE and CG effects showed similar trends. Animal genetic effect seemed to be less variable on the longitudinal scale compared with other random effects of the model. The first 2 principal components explained from 95% (PE effects) to 99% (genetic effect) of the total variance. The overall level of genetic stayability curve correlated well (from 0.87 to 0.99, with SD < 0.006) with genetic stayability to different calvings and therefore could be used as a single criterion in selection for stayability. © 2013 American Society of Animal Science. All rights reserved. Source

Jamrozik J.,University of Guelph | McGrath S.,RAK Genetic Consulting Ltd | Kemp R.A.,RAK Genetic Consulting Ltd | Miller S.P.,University of Guelph
Livestock Science

Calving to first insemination (CFI) (probability that a cow will produce a calf from her first service) and days to calving (DC) (interval between the first exposure to the bull and calving) defined separately for heifers and multi-parity cows were analyzed with a 4-trait linear animal model. The data were 108,206 records on 56,879 Canadian Simmental females with artificial insemination (AI) and natural service (NS) breeding records from 1974 to 2010. The model included fixed effects of year-season of breeding, age of cow by season of breeding, and age of cow's dam. Random effects were: contemporary group defined as herd within breeding year-season by breeding status for the first insemination (AI or NS), service sire by year of breeding (for CFI only), animal genetic, and cow permanent environmental (PE) effects. Bayesian methods were used to estimate covariance components and genetic parameters. Three specific models with different levels of heterogeneity for covariances in NS and AI data were tested. Results are reported for the most plausible specification which was the model that assumed different residual covariances for NS and AI records. The data exhibited substantial heterogeneity of residual covariance components with respect to the type of first breeding, with AI records having larger residual variances for both traits. Pooled estimates (SD) of heritability ranged from 1.8% (0.33) for CFI in heifers to 3.5% (0.47) for DC in multi-parity cows. Interval trait (DC) had higher heritability compared with CFI; both traits expressed in older cows were more heritable than corresponding traits for heifers. Contemporary group contributed up to 58% (0.51) of the total variance for DC in heifers by NS breeding. Service sire and the PE were relatively larger (smaller) sources of variation compared with additive genetic (contemporary group) effects. All traits were highly genetically correlated: from 0.69 (0.06) for CFI in heifers and multi-parity cows to 0.92 (0.04) for DC in heifers and multi-parity cows. Environmental correlations ranged from -0.73 (0.01) between CFI in heifers and DC in older cows, to 0.91 (0.01) for DC in heifers and multi-parity cows. Results indicated that CFI and DC expressed different aspects of female fertility in beef cattle, and fertility of heifers and multi-parity cows seemed to be different traits genetically. All four traits could be used in a form of selection index in Canadian Simmentals to breed for better fertility. Genetic progress, however, would be challenging given low values of heritability. © 2012 Elsevier B.V. Source

Discover hidden collaborations