Effects on wool production during pregnancy and lactation of twice daily abomasal supplementation with casein or methionine and cystine

Abstract

The responses in wool production of Merino ewes to abomasal supplements of casein (56 g day-1) and of a mixture of methionine and cystine were measured during late pregnancy and early lactation. The mixed supplement provided equal quantities of the sulphur amino acids as the casein. The ewes were offered sufficient quantities of a diet of sorghum grain/lucerne hay (in the ratio 7 : 3 by weight) to maintain maternal liveweight. During the final four weeks of pregnancy and the first six weeks of lactation, the cassin supplement increased wool growth (826 vs. 639 g cm-2 day-1). A similar response was observed for fibre diameter (1 9.7 vs. 18.5 pm : P < 0.05). Wool production and fibre diameter did not differ between the ewes supplemented with methionine and cystine and the control ewes during this same period. The ewes supplemented with methionine and cystine produced wool with the greatest sulphur content, and this trait was least in the wool from the control ewes (3.84 vs. 3.64 vs. 3.49: P < 0.05). We concluded that the availability of the sulphur amino acids was not primarily limiting wool production in pregnant/lactating ewes.