Urea as a protein source for ewes with twin lambs in late pregnancy and early lactation

Abstract

SUMMARYIn three experiments housed Greyface (Border Leicester × Scottish Blackface) ewes of mean live weight 68 kg received 0·91 kg hay plus 0·91 kg molassed sugar beet pulp daily during the second half of pregnancy and in the first 3 weeks of lactation. Comparisons were made with additions of crude protein given as urea or groundnut cake either during the whole period or only during early lactation. In one experiment, increasing the daily intake of digestible crude protein from 88 to about 140 g had no effect on the weight of the lamb at birth or at 3 weeks. In the other two experiments, in which the increases were from 58·70 g to 131·161 g or from 80 to about 125 g digestible crude protein per day there were highly significant increases in the weight of the lamb at birth (+0·43 and +0·31 kg) and 3 weeks (+1·44 and +1·46 kg). Introduction of either urea or groundnut cake to the diet on the day after lambing significantly increased the the 3-week weights of the lambs by amounts which were comparable to those found when urea had also been given during pregnancy. Supplementation with either urea or groundnut cake did not significantly increase ewe live weight.Concentrations of urea in the blood of the ewes were highly significantly increased by either urea or groundnut supplementation. There were indications that a concentration below 10 mg/100 ml in the blood of the ewes in late pregnancy or early lactation was associated with a reduction in lamb growth rates.