Whole wheat grain feeding of Merino ewes. 2. Influence of wheat and vitamin A on reproductive performance

Abstract

In two experiments Merino breeding ewes were fed wheat in pens (wheat/pen) or small paddocks (wheat/paddock) from joining to weaning. Three levels of wheat were examined in each experiment (L1, M1, H1-experiment 1 ; L2, M2, H2-experiment 2) and at each wheat level a group of ewes received vitamin A. Control groups of ewes were run at pasture. The percentage of ewes pregnant in experiment 1 was higher in groups fed pasture than in groups fed wheat. There were no differences due to wheat level or vitamin A treatments. In experiment 2 there was an interaction between treatments in their effects on pregnancy rate. In experiment 2 wheat level had a linear effect on the proportion of multiple births and wheat/pen ewes gave birth to fewer twins than wheat/paddock ewes. The effects of wheat level on lamb birth weight were linear and quadratic in experiments 1 and 2 respectively. Lamb survival between birth and weaning was not influenced by wheat level or vitamin A in experiment 1. Lamb survival among groups fed wheat and pasture was 46 per cent and 84 per cent respectively. In experiment 2 there was an interaction between the treatments in lamb survival. In experiments 1 and 2, 66 per cent and 53 per cent respectively of lamb deaths among groups fed wheat were attributed to starvation. Goitre was diagnosed in 9 per cent of dead lambs from the wheat/pen groups of experiment 2. In both experiments white muscle disease was found in dead lambs from the wheat/pen groups.