Examination of selection index weights for lamb production

J.W. Skerritt, P.R. Amer and G.B. Nicoll

Landcorp Farming Limited, PO Box 1235, Hamilton, New Zealand.

E-Mail:

Proceedings of the New Zealand Society of Animal Production. 1998, 58: 146-149

Economic values for lamb production have historically been derived with the assumption that lambs are slaughtered at a constant age. However, Landcorp Farming Limited slaughters lambs when they reach a set carcass weight. After weaning, heavier lambs are given preferential feeding and slaughtered when they reach a predicted carcass weight of 15kg. In this study index weights for weight of fat (FAT) and weight of lean (LEAN) in the carcass are calculated based on the different costs and returns associated with finishing lambs at a set weight. The nonlinear profit function was responsible for a positive index weight being derived for FAT. This result highlights the problems with using FAT and LEAN as selection criteria for lamb production. It is pointed out that FAT and LEAN are not breeding objectives for sheep production, and that it may be possible to use selection criteria better related to the profit function.

Keywords: NZSAPAB; economic values; lean; fat; sheep; meat; weight.

Last Updated 12-09-1998