An investigation of the optimum slaughter weight of early weaned lambs
Whereas lambs of woolled-mutton and mutton-woolled breeds are slaughtered locally at a live weight of approximately 32 kg, commensurate with the time of weaning, this experiment was planned to investigate the economic possibility of delayed slaughtering of early weaned lambs to beyond this weight. In total 152 lambs of the Merino (M), Dohne Merino (Do), German Mutton Merino (DM) and Dormer (DR) breeds, subsequent to weaning at eight weeks of age, were fed on a ration consisting of chopped lucern hay (17,3% crude protein) and concentrate feed pellets (9,0 % crude protein).Groups of lambs were slaughtered at the attainment of mean live weights of 27, 32,37 and 42 kg. Carcasses were subjectively graded and also scored according to the procedure described by Starke & Joubert( 1961). From a carcass evaluation point of view it emerged that slaughtering weights of 27 and 32 kg were too low for Dohne Merinos and particularly for Merinos. At the higher slaughtering weights there appeared to be no statistical significant differences between the grades awarded to carcasses from different breeds. Marginal cost and income analysis indicated that slaughtering this type of early weaned lamb at a higher weight than 32 kg is profitable. The financial benefit to be derived from later slaughtering varies between breeds, with a lowest value in the case of the Merinos (due probably to the longer feeding time required). As a mean of all breeds the financial benefit resulting from slaughtering at 42 kg instead of at 32 kg was 79 cents/lamb in one experiment and R1.00 in another. The comparable figure for slaughtering at 37 kg instead of at 32 kg indicated a benefit of 30 cents/lamb. ln contrast it was evident that slaughtering at an earlier stage than at 32 kg, could not be approved on economic grounds under the circumstances of the present experiment.