Soya bean meal, crystalline urea, and a urea, mineral and vitamin solution as nitrogen sources for lactating ewes given whole oats

Abstract

ABSTRACTFifty-one ewes with single lambs and 87 ewes suckling twin lambs (mean ewe live weight, 67 kg) were given a basal diet of 1·0kg hay and 1·0kg whole oats, providing approximately 16·7MJ metabolizable energy and lOOg digestible crude protein per day. Three supplements (A, B and C), providing an additional 45 g digestible crude protein, were compared. Supplement A consisted of 40 g of a fully-soluble liquid product (LS) containing urea, (equivalent to 1090g crude protein per kg), minerals and vitamins; B was 16g urea with solid minerals and vitamins; and C was 125g soya bean meal given in substitution for the same amount of whole oats plus solid minerals and vitamins. The growth rate to 6 weeks for single lambs (11 kg) was unaffected by treatment. For twin lambs the growth rates were 7·5kg (LS), 7·1kg (crystalline urea), 7·8kg (soya) and 6·4k g (unsupplemented) (s.e. of mean = 0·31 kg). Ewes with twin lambs given crystalline urea or LS lost more live weight (approximately 1·04kg) than those given soya (6·6kg) over the first 6 weeks of lactation. The maintenance of normal concentrations of calcium and phosphorus in the blood of ewes suggested that the low total intakes of approximately 4·1 g calcium and 4·7 g phosphorus by the ewes were not inadequate.