GENETIC-PARAMETERS FOR AUSTRALIAN MATERNAL AND DUAL-PURPOSE MEATSHEEP BREEDS .1. LIVEWEIGHT, WOOL PRODUCTION AND REPRODUCTION IN BORDER LEICESTER AND RELATED TYPES

Analyses of two separate Border Leicester data sets are reported. In the first set, genetic parameters were estimated for 14 month liveweight and greasy fleece weight from 1312 ewe and ram records representing 75 sires of the Border Leicester and Glen Vale breeds (a related genotype) using derivative-free REML procedures. The heritability estimate for liveweight was 0.24+/-0.07 and greasy fleece weight was 0.17+/-0.05, with the genetic correlation being -0.21+/-0.30 and phenotypic correlation 0.54+/-0.02. In the second data set, reproductive performance was analysed and genetic parameters were estimated from 7395 joining records for 1604 ewes, representing 165 sires, from two Border Leicester stud flocks. Reproduction traits analysed were fertility (ewes lambing of ewes joined), litter size (lambs born per ewe lambing) and lambs born (per ewe joined). The studs differed in performance for all reproductive traits; fertility (67 v. 82%), litter size (1.27 v. 1.43) and lambs born (85 v. 117%). The estimates of heritability and repeatability respectively for ewe performance were: fertility 0.01+/-0.01 and 0.05+/-0.01, litter size 0.01+/-0.02 and 0.05+/-0.01, lambs born 0.00+/-0.01 and 0.06+/-0.01. Estimates of heritability for average ewe lifetime performance were 0.04+/-0.05 for fertility, 0.02+/-0.05 for litter size and 0.03+/-0.05 for lambs born, based on averages of 4.6 joining and 3.5 litter size records for ewes. The genetic correlations between lambs born and its components fertility (0.96+/-0.18) and litter size (0.83+/-0.44) were high, with the genetic correlation between fertility and litter size being 0.65+/-0.52. Implications for breeding programs for Border Leicester flocks within LAMBPLAN are discussed.