Influence of litter size and breed of sire on carcass weight and quality of lambs

Abstract

SUMMARY In order to obtain a wide range of live weights, two Oxford Down, two Southdown, and two Soay rams of recent feral origin, were used to sire lambs from 169 crossbred ewes. These ewes had been bred from Blackface ewes mated to Border Leicester, Dorset Hora, Clun Forest, Finnish Landrace and Tasmanian Merino rams. Of the 282 lambs weaned by the crossbred ewes, 61 were singles, 166 twins, 51 triplets and 4 quadruplets. Carcass data were obtained from all but three of them. Oxford Down cross lambs were, in terms of fitted values, 10 kg heavier and 4 days younger than Soay cross lambs and 6 kg heavier and 2 days younger than Southdown cross lambs when slaughtered. Twins and triplets were 1·4 and 2·1 kg, respectively, lighter than singles and were 37 and 58 days older than singles. Ewes of the heaviest groups produced heavier lambs in a shorter time than ewes of the lightest groups. The Soay cross lambs showed a higher killing-out percentage, less tail fat, and more kidney fat, than the Southdown and Oxford Down cross lambs. Carcass characters made little if any difference to the price paid for the lambs which depended mainly on weight. Receipts from lambs were highest when the most fertile ewes were mated to the largest rams.