Verifying carcass trait changes in a backcross programme with Texel Breed

A backcross programme of the Polwarth breed (Ideal breed, I) to Texel breed was carried out at the Experimental Station of the Universidad Nacional de Rosario, Argentina. Males and females lambs of the Ideal and new breed, named Magrario(M) were evaluated for post weaning growth during two months, under two feeding systems: FT (Feedlot) and RT (Range). Their carcasses were assessed following the EAAP Standard Method (1994). Also, postweaning relative Average Daily Gain (rADG) and Final Live Weight (FLW) were analysed. Significant differences were observed for rADG and FLW traits between environmental conditions in each genotype (p < 0.001) and between males of M and I genotypes in FT (p < 0.01). A Principal Component Analysis (PCA) with nineteen carcass traits, also including rADG and FLW, showed that 91% and 87% of the total variance was explained for the first two components in FT and RT respectively. In both feeding systems, highest values were found for FLW, cold carcass weight, and several others limb weight traits in PC1, whereas thickness of subcutaneous fat and total lean weight were highest PC2. These results showed the influence of Texel genotype on these carcass components showing that EAAP assessment carcass methodology, together with the PCA applied, were appropriate tools to verify the success of this programme to improve carcass traits. In those different feeding systems, genes from Texel breed have provoked significant carcass changes being these more evident in feedlot conditions.