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 0075 /day for 21 weeks divided into 3 equal periods. Intake, wool growth, and body growth were considered relative to body weighto' 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 o . 75 did not differ between breeds or periods. On a pooled within-breed, within-period basis, wool growth/ body weight o . 75 (r = 0.69) and fibre diameter (r = 0.69) were correlated with DM intake/body weight 0075 • During the last 2 periods the sulphur content of the fleece wa:o correlated within breeds (r = 0.62) with DM intake/body weighto. 75 • Fibre diameter (r = 0.76) and sulphur content of the fleece (r = 0.62) were correlated with wool growth/body weight o · 75 • The regression coefficient for the regression of clean wool/body weight o . 75 on DM intake/body weighto. 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 o . 75 at an intake of 40 g DM/body weight o . 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. 251

Effects of pasture allowance in winter on liveweight, wool growth, and wool characteristics of Romney ewes

“…In each winter period the wool growth response to pasture allowance and potential wool growth were both much less than in experiments at Woodlands in other seasons . This is consistent with the interaction of season with the effect of nutrition on the wool growth of longwoo lied breeds demonstrated in several studies (Sumner 1979;Hawker et al 1984;Hawker & Crosbie 1985). The relative response of wool growth to feeding level is similar in all seasons but the absolute response is directly related to the wool growth rate of ewes held at zero liveweight change, i.e., the winter response is only 30 -50070 of that in summer.…”

Seasonal variations in the dimensions of individual Romney wool fibres determined by a rapid autoradiographic technique

“…The seasonality in wool growth may be accentuated by nutritional level (Sumner 1979;Hawker et al 1984). Thus the seasonal changes in fibre diameter and length-growth shown by Sheep 381 may have been exaggerated by its loss in liveweight which presumably resulted from a lowered food intake.…”