The estimation of (co)variance components growth, reproduction, carcass, FECS and FECN traits in Lleyn sheep

Genetic parameters for weaning live weight and ultrasound scanning measurements were estimated from performance recorded UK Lleyn sheep. The data for the study were collected from conventional hill and low land farming systems. The data were from 48,277 lambs. Genetic parameters were estimated using uni- and bivariate animal models for weight at birth (BWT), live weight at 8 weeks (8WK), ultrasound scanning at 21 weeks of age (SWT) and weight at tupping (MW), ultrasound scanned muscle (MD) and fat (FD) depth measured at 21 weeks of age, litter size born (LSB), litter size reared (LSR), faecal egg count for strongyle (FEC_S) and nematodes (FECN). Maternal genetic effects were fitted for BWT, and 8WK. Direct heritability estimates were 0.14 ± 0.01 for BWT, 0.35 ± 0.02 for 8WK, 0.46 ± 0.01 for SWT, 0.31 ± 0.01 for MD, 0.38 ± 0.01 for FD, 0.38 ± 0.01 for MW, 0.22 ± 0.09 for FEC_S and 0.16 ± 0.10 for FECN. Maternal heritability estimates were 0.14 ± 0.01 for BWT and 0.11 ± 0.01 for 8WK. Direct genetic correlations among studied traits ranged from −0.05 (MW–FD) to 0.90 (SWT–8WK). Phenotypic and environmental correlation estimates were generally lower than those of genetic correlation. Our results indicate that the genetic parameters generated in this study could be used in selection index calculations to asses the benefits of including lamb carcass traits in future selection programmes for Lleyn sheep. Also, this study provides valuable information in terms of genetic parameters for growth and carcass traits which can be used for genetic evaluation and in designing selection programmes for the Lleyn breed.