The comparative productivity of five ewe breeds. 4. Growth and carcase characteristics of purebred and crossbred lambs

Abstract

The growth to slaughter and carcase characteristics of purebred and crossbred lambs from five ewe breeds were compared in an experiment in 1971 and 1972 at Temora Agricultural Research Station. The ewe breeds were a Border Leicester x Merino fixed halfbred (BLM), Corriedale, Polwarth, a South Australian strong wool (SA Merino) and a medium wool Peppin strain of Merino. In each year, ewes of each breed were joined either to their own breed of ram or to Dorset Horn rams. The analysis used tested whether differences between ewe breeds in crossbred performance were halved compared with the differences between ewe breeds in purebred performances. The results supported this hypothesis for all characters measured. The largest breed effects on lamb performance were found for growth rate. Compared with the overall mean, the growth rates to weaning for purebred lambs were 118%,102%, 90%, 99% and 91% 10 for the BLM, Corriedale, Polwarth, SA Merino and Peppin Merino, respectively. The deviations from 100% for crossbred lambs were halved. Differences between breeds for carcase traits were estimated at the same carcase weight. South Australian Merino lambs had a lower dressing percentage than lambs from .the other breeds. Polwarths had the greatest depth of fat at the 12- 13th rib. Skins from Merino lambs had shorter staples and higher visual counts than skins from the other breeds. However, it was concluded that breed differences in carcase and skin characters, independent of carcase weight, were of little value in an economic comparison of the breeds for total productivity.