Whole wheat grain feeding of lambs. II. Growth of Merino lambs early weaned onto wheat

Two experiments were conducted to examine the growth characteristics of Merino lambs early weaned onto a base diet of whole wheat grain plus 1 .5 % limestone ad libitum. These data have been compared with similar information obtained for traditionally managed spring drop Merino weaners at pasture. In experiment 1, 158 lambs which were born to ewes given wheat in pens were used in a 4 x 2 factorial to examine responses to anti-white muscle disease compounds and biuret. No responses were obtained to selenium, vitamin E, or a combination of the two. The food conversion efficiency (FCE), i.e. weight units of feed ingested per weight unit increase in liveweight, was improved by addition of 3 % biuret (5.1 v. 5.5 for control). In experiment 2, 185 lambs were used in a 5 x 2 factorial where minerals and biuret were the factors. These lambs originated from groups of ewes fed on either wheat or roughage in paddocks. There was a 28.6% mortality in lambs without previous exposure to wheat when this group was early weaned onto a pasture-clover hay ration which changed over 37 days to 100% wheat. The mortality among lambs with wheat experience was 1 .5 % during this period when they were offered wheat ad libitum from weaning. Responses to biuret were small and variable, while a positive response to sodium, which was present in all four mineral treatments, was obtained. In comparison with control animals, the effects of including sodium were to reduce FCE (5.2 v. 4.7), reduce the time to finish (123 v. 111 days), and increase the rate of gain (0.84 v. 1.03 kg/week).