Genetic parameters of weights, ultrasonic muscle and fat depths, maternal effects and reproductive traits in Welsh Mountain sheep

Abstract

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.

Estimation of meat amount by non-linear multiple regression equations using in vivo and carcass measurements on Teleorman Black Head lambs

“…The observed body weight at birth and weaning was within the normal limits for TBH breed (Lazar et al, 2009;Ghita et al, 2010), 10.88% higher than the body weight at birth reported by Dewi et al (2002) for Welsh Mountain lambs. The TBH lambs were slaughtered 12 and 6 days earlier than reported by Dewi et al (2002) for Welsh Mountain lambs and by Peña et al (2005) for Segurena lambs, respectively.…”

“…), and their biggest disadvantage is that the selected animals could no longer be used for reproduction. Hence, the trend was to remove these inconveniencies by improving the carcass grading techniques (Dewi et al, 2002). The ultrasound measurement is a new technique which is a non-invasive, efficient grading method for classification and quantification of the animal carcasses in their early life as well as the further usage of animals for reproduction.…”

Genetic Parameters for Growth Traits of the Hungarian Merino and Meat Sheep Breeds in Hungary

“…The population has changed in the last 8 years, and different breeds were also introduced in Hungary. Several estimates have been published for sheep traits (de Vries et al, 1998, Ap Dewi et al, 2002;Safari et al, 2005). The genetic parameters are population specific.…”

Exploration of cytoplasmic inheritance as a contributor to maternal effects in Welsh Mountain sheep

“…Maternal additive genetic, 2 : maternal permanent environmental variance expressed as a proportion of phenotypic variance; ce 2 : maternal common environmental variance expressed as a proportion of the phenotypic variance; cy 2 : cytoplasmic genetic variance expressed as a proportion of phenotypic variance; -2*logL: log likelihood ratio test: AIC: Akaike Information Criterion; BIC: Bayesian Information Criterion. Value in bold shows the chosen model according to test statistic.…”

“…where μ = is the overall mean of eight-week weight, scan-weight, muscle depth or fat depth; a i = fixed effect of rearing dam age (4 age classes: 2, 3, 4-6, 7+); The significance of the cytoplasmic effect was determined using a likelihood ratio test (P = 0.05), a method widely used to compare models in these types of analyses [2,8,11], and was considered to have a significant influence when its addition in Model 2 caused a significant increase in -2*logL, compared to Model 1 without the effect. The test statistic follows a 50:50 mixture of chisquared distributions with respectively 0 and 1 degree of freedom, therefore at a significance level of 0.05 a critical value of 2.79 was used.…”