Comparison of the fat status of lambs during continuous growth and following nutritional restriction and subsequent re-alimentation

Abstract

Crossbred lambs were allocated to one of four treatments: continuously grown at pasture; weaned and fed hay to maintain liveweight at 32 kg for 120 d and re-alimentated by grazing at pasture; fed peas and hay ad libitum or at restricted levels in a feedlot. The lambs were slaughtered at 32, 37,42 and 47 kg unfasted liveweight. Results of multiple regression analyses showed that carcasses of the continuously grown lambs contained significantly more subcutaneous fat in the 9th- 12th rib cut and significantly more kidney and channel fat than the carcasses of the re-alimentated lambs. Similar results were obtained from measurements of the depth of subcutaneous fat at 13 sites on the carcass and from subjective appraisal of fat status. The equations showed that these effects were greatest at carcass weights of 14- 17 kg and that the difference in fat status lessened as carcass weight of the re-alimentated lambs increased. During re-alimentation, neither the rate of carcass gain nor type of diet significantly affected the various measurements of fat status.