Studies on the shearing of housed pregnant ewes

Abstract

ABSTRACTTwo experiments were conducted in successive years with, respectively, 112 and 194 mature Scottish Blackface ewes to study the effects of shearing during pregnancy on lamb birth weight and subsequent growth. In each year half the ewes were shorn approx. 10 weeks before lambing. Shorn and unshorn ewes were offered and consumed equal quantities of food.In both years the shorn ewes lost approx. 2 kg of live weight shortly after shearing (making allowance for the weight of wool removed); thereafter live-weight differences remained relatively constant. Plasma 3-hydroxybutyrate concentrations indicated that the initial live-weight loss was probably attributable to short-term increases in heat production and energy expenditure.Respiration rates and rectal temperatures of unshorn ewes were always higher than in shorn ewes, but were not elevated to an extent indicative of heat stress.Shearing had no effect on the birth weights of single or twin lambs, nor was there any effect on lamb growth rate to 14 weeks of age.It is postulated that the effects of shearing on lamb birth weight reported by others working with sheep fed ad libitum are most likely to be due to the increased voluntary food intakes of shorn ewes.