No abstract

Summary Residual maximum likelihood procedure was applied to analyse data from a one‐to‐one pedigreed Japanese quail population, using an animal model to estimate the genetic parameters of weekly liveweights. Records of 1108 animals from 113 sires and 152 dams were analysed. An individual animal model was used. The heritabilities of weights for hatching (HW) with their standard errors (SE), week 1 (W1), week 2 (W2), week 3 (W3), week 4 (W4), week 5 (W5) and week 6 (W6) were 0.51 ± 0.05, 0.32 ± 0.06, 0.20 ± 0.05, 0.21 ± 0.06, 0.20 ± 0.05, 0.15 ± 0.04 and 0.14 ± 0.04, respectively. The strongest genetic correlations were found between W1 and W3 (0.98 ± 0.11). Generally, genetic correlations were higher than the phenotypic correlations. The highest phenotypic correlation (0.85) was between the W4 and W5 weights. Strong genetic correlations among the weekly weights suggest that selection for W5 or W6 weight may be based on weights recorded earlier.

Fully pedigreed records of a Japanese quail population were analyzed for genetic parameters of egg and BW traits. A restricted maximum likelihood (REML) procedure was applied in univariate and bivariate analyses. Quantitative genetic analyses, including maternal effects, were carried out on the records of 947 male and 861 female birds (total = 1,808). The traits were analyzed with bird as a random factor to fit the additive direct effect, bird being the individual for which the trait was recorded, namely hen (dam) for egg traits and chick (progeny) for BW. Permanent environmental effects (0.29 to 0.35) on egg traits were higher than corresponding heritabilities (0.18 to 0.25). Significant maternal genetic and maternal permanent effects were measured for hatching BW. The heritabilities of weekly BW were low, and decreasing by 5 to 6 wk of age. They were 0.07, 0.18, 0.19, 0.18, 0.19, 0.13, and 0.15 from hatching to 6 wk, respectively. Strong correlations were detected between direct genetic effects for egg traits and maternal genetic effect for BW traits. Applying such detailed analyses in the study of both egg and BW traits provides procedures to specifically evaluate Japanese quail and poultry in general. The results illustrated that the maternal permanent environmental effects made larger contributions to the variability of egg traits than did direct genetic effects. This situation implies that rearing of birds, healthcare, and feeding are very important determinants of egg characteristics.

The purpose of this study was to examine the importa~zce of the genetic arld maternal enviroizmental factors ilifluencing the 12-week weight ( 1 2 W W ) of Welsh Mountain lambs arzd to estimate genetic parameters for this trait. Records of 8880 Welsh Mourztain lambs borrl betweeiz 1979 and 1995 were analysed. The records werefrom the rlucleus flock of the C A M D A cooperative breeding group. In this flock selection of replacements had been based on a multi-trait index incorporating lamb growth and materrzal ability as importaizt objectives and 1 2 W W as one of the selection criteria. Twelve models were examined, all including direct additive genetic variance urzd various combinations of genetic and environmental maternal effects. The most appropriate model was chosen based oil loglikelihood ratio tests. It included appropriate fixed effects, and direct additive, maternal additive, maternal permanent environment and maternal common environment (litter) random effects that defined proportionally 0.21 (h2), 0.09 (mZ), 0.06 (pe2) and 0.18 (ce2) of the pherlotypic variance. Ignoring the additive maternal effect resulted in inflated estimates of direct heritability and ignoring the environmental effects associated zuith dam irzflated the direct and maternal heritabilities. There was no correlation (P < 0.05) between the additive direct and additive maternal effects. Additive direct and maternal breeding values increased by 0.12 (s.e. 0.006) kglyear and 0.03 (s.e. 0.003) kglyear respectively. The results demonstrate the effective incorporation of selectiorl index methodology in the context of a hill sheep flock and also the importance of several categories of maternal effects.

Genetic parameters of weight traits, ultrasonic fat and muscle depths, maternal effects and reproductive traits of Welsh Mountain sheep were estimated based on analyses of data from the nucleus flock of a cooperative breeding scheme. The traits analysed were 12 week weight (TW, no. = 11201), mature weight (MW, no. = 2376), weight at scanning (SW, no. = 1022), muscle depth (SM, no. = 1024), fat depth (SF, no. = 1024), litter weaning weight (LW, no. = 3445) and litter size (LS, no. = 3445). (Co)variance components were estimated in univariate and bivariate animal models. Heritability estimates from univariate analyses were 0.16, 0·49, 0·29, 0·24, 0·22, 0·20 and 0.15 for TW, MW, SW, SF, SM, LW and LS respectively. Genetic correlations among the weight traits were high. There was no detectable correlation between SF and SM. SF and SM were strongly correlated with SW but not with the other weight traits. LW was strongly correlated with MW and SW but not with TW, although the latter analysis was inconclusive. Maternal heritability was similar (0·11) for the univariate analysis of TW and all bivariate analyses involving TW (except for TW v. LW). The permanent environmental effect of dam was generally low (0.02 to 0.04) whilst litter effects were generally high (0·20 to 0·23). The correlation between direct and maternal genetic effects for TW were generally small and non-significant. The maternal genetic effect for TW was moderately correlated with the direct additive effect for MW and SW but was not significantly correlated with the direct additive effect for LS, SM or SF. A very large positive correlation was found between the maternal genetic effect for TW and the direct additive effect for LW. The implications of the results are discussed in the context of selection indices for Welsh Mountain sheep.