Abstract

Purebred Texel and Suffolk sheep have been grazed together at Belclare in Ireland since 1977. The Texel sheep originated from the Netherlands and are of similar origin to those imported into New Zealand. A series of studies have been undertaken to examine the growth and carcass composition of the 2 breeds. Relative to the Suffolk the Texel has an altered growth patter; Texel lambs were 19% heavier at birth than Suffolk lambs after adjustment for non-genetic effects, but by weaning were 8% lighter (29.08 v 31.76 kg) and the difference increased to 11% at 2.4 years of age. The difference between the Purebred Texel and Suffolk weaning weights is approximately double the value that has been reported in large scale crossbreeding trials. Wool production in the Texel was 12 to 22% higher than the Suffolk breed depending on age. Carcass composition data from 2 separate slaughter trials, using ram lambs, show that the purebred Texel has less subcutaneous fat as a proportion of the carcass than the Suffolk with 75 v 112 g/kg for 18.6 kg carcasses in the first trial and 34 v 80 g/kg and 83 v 125 g/kg when killed at 17.3 and 26.1 kg carcass weight in the second trial. When expressed as a percentage these breed differences are approximately double the values observed in crossbreeding trials. The Texel carcasses also had larger L. dorsi areas and less fat in the internal depots. The food efficiency in the Texel breed was better in the 2 experiments where it was measured, with the differences being significant in 1 trial. Breed differences in composition persisted to maturity with adult Texels having only 78, 81 and 90% of the weight of subcutaneous, kidney knob, and channel and omental fat deposits relative to the Suffolk. In vivo ultrasonic measurements distinguished similar changes in carcass composition between the breeds with C, Gr and estimated L. dorsi in purebred Texels being 85, 78 and 111% of Suffolk ewe and ram lambs. The corresponding figures for adult ewes were 79, 83 and 107%. The carcass composition of most sheep breeds are very similar when expressed as a proportion of mature live weight. The data presented suggests that the Texel is atypical having a modified growth curve and retaining its extreme carcass composition even at maturity.

BS, Thorrold, AH Kirton, LJ Cranshaw, and GJK Mercer

Proceedings of the New Zealand Society of Animal Production, Volume 48, , 19-24, 1988