Genetic and phenotypic parameters associated with lean tissue growth in Dorset Down sheep.

S.J. Nsoso, M.J. Young, P.R. Beatson, S.T. Bell.

Animal and Veterinary Sciences Group, Lincoln University, Canterbury, New Zealand.

Proceedings of the New Zealand Society of Animal Production 1994, 54: 251-254

Genetic and phenotypic parameters were estimated using multi-variate AIREML analyses by fitting an individual animal model with animal as a random effect, birth rank, age of dam and year of birth as fixed effects and age at measurement as a covariate. Multi-variate heritability estimates (± s.e.) for live weight, fat and muscle depths were 0.42 (±0.04), and 0.30(±0.05) for rams and 0.26(±0.01), 0.20(±0.05) and 0.13(±0.03) for ewes respectively. Estimates of genetic correlations were generally moderate to high for the two sexes. The genetic correlation between live weight and fat depth was significantly different for the two sexes, with rams (0.42±0.10) having a higher value than ewes (0.24±0.02). Phenotypic correlations differed between the sexes, with estimates for ewes being slightly higher. For both sexes, parameter estimates were different from those used to derive the indices used to select for lean tissue growth, ram estimates being consistently higher while those for ewes were more equivocal.

Keywords: NZSAPAB; genetic parameters; phenotypic parameters; lean tissue growth; live weight; fat depth; muscle depth; sheep; selection.