Intakes of silages, hays and straws by ewes in mid pregnancy

Abstract

ABSTRACTIn three experiments, seven grass silages, four grass hays and winter barley straw, with and without anhydrous ammonia treatment, were offered ad libitum to a total of 134 Finn Dorset ewes in weeks 11 to 15 of pregnancy and intakes were measured. The untreated straw diet was supplemented with 300 g fresh weight of concentrates per ewe. Number of foetuses carried did not affect intakes in mid pregnancy. Organic matter digestibilities measured in vivo in week 15, ranged from 0·39 to 0·69 for hays and 0·53 to 0·79 for silages. Generally, between weeks 11 to 15 of pregnancy, hay intakes showed either little change or slight increases whereas intakes of silages or straws showed little change or slight decreases. Forage intake was higher on the better quality hays and silages and ewes gained weight and body condition, compared with losses for the poorer diets. In late pregnancy, the ewes were offered grass silage ad libitum and rations of concentrates according to a rationing programme. There were no residual effects of the mid-pregnancy treatments on lamb birth weights but ewes offered the poorer diets in mid pregnancy still tended to be lighter and thinner post partum. Equations are presented to predict the intakes of hays and silages from food and animal factors.