The performance of weaned lambs offered diets containing different proportions of fresh perennial ryegrass and white clover

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Abstract
Six weaned lambs were allocated to each of eight restricted feeding treatments with 1·00, 0·85, 0·71, 0·57, 0·43, 0·29, 0·15 or 0 of the diet as perennial ryegrass and the remainder as white clover, and to one ad libitum treatment with perennial ryegrass offered alone. A further six lambs were offered white clover ad libitum starting on day 15. Lambs on the restricted treatments received the same daily allowance of dry matter relative to live weight, adjusted at weekly intervals to allow the greatest possible intake without any rejection of herbage. Fresh cut herbage was offered daily and measurements were made over 69 days. Twelve additional lambs were slaughtered at the beginning of the experiment, and all lambs on restricted treatments were slaughtered at the end.Increasing the proportion of clover in the diet increased the intake of nitrogen, empty-body-weight gain, carcass weight gain and nitrogen retention. When herbage was offered ad libitum, lambs ate significantly more clover than ryegrass and gained weight faster.The weight of gut contents decreased as the proportion of clover in the diet increased. The digestibility of the organic matter, energy and nitrogen of the mixed diets simply reflected the digestibilities of the two herbages and their proportions in the mixture.