The effect of milk intake on the intake of cut and grazed herbage by lambs

Fifty-three lambs were artificially reared from 1 day old. From 14 days of age they were either housed and offered cut herbage or grazed at pasture. Five milk feeding treatments were allocated to both the housed and the grazing lambs; these were a total of 50, 70, 90 and 110 kg of ewes' milk given over 12 weeks and milk substitute for 4 weeks. Three additional lambs were housed and offered milk ad libitum . Digestibilities of the dietary components, herbage and milk intakes and lamb growth rates were measured. Similar digestibility coefficients were obtained for milk and for herbage when consumed together compared with individually. Milk intake was negatively correlated with herbage intake and positively correlated with growth rate. Under conditions permitting ad libitum intake, lambs at pasture had higher intakes of herbage than lambs offered cut herbage indoors. Equations are given which enable herbage intake at a particular age to be predicted from total milk intake.