Efficiency of wool and body growth in pen-fed Romney, Coopworth, Perendale, and Corriedale sheep

Abstract

Ten 1-year-old sheep of each of the breeds were pen-fed a pelleted diet of 60:40 maize: lucerne at 30, 40, 50, 60, or 70 g/kg initial live weight^0·75 /day for 21 weeks divided into 3 equal periods. Intake, wool growth, and body growth were considered relative to body weight^0·75 to allow for the effect of between-breed differences in body size. Estimates of the conversion of dry matter (DM) intake/body weighto.75 to body weight gain/body weight^0·75 did not differ between breeds or periods. On a pooled within-breed, within-period basis, wool growth/ body weight^0·75 (r = 0.69) and fibre diameter (r = 0.69) were correlated with DM intake/body weight^0·75. During the last 2 periods the sulphur content of the fleece was correlated within breeds (r = 0.62) with DM intake/body weighto^0·75. Fibre diameter (r = 0.76) and sulphur content of the fleece (r = 0.62) were correlated with wool growth/body weight^0·75. The regression coefficient for the regression of clean wool/body weight^0·75 on DM intake/body weight^0·75 did not differ between breeds but increased between periods as the seasonal wool growth maximum was approached. The intercepts were different between breeds and decreased between periods. The ranking of breeds for clean wool/ body weight^0·75 at an intake of 40 g DM/body weight^0·75 /day was Corriedale, Coopworth, Romney, and Perendale in the winter and spring and Coopworth, Corrieda1c, Romney, and Perendale in the early summer. The regression coefficients for the regression of both fibre diameter and sulphur content of the fleece on clean wool/body weighto.75 did not differ between breeds or periods. The intercepts, which differed between breeds, did not differ between periods.