Abstract

The paper takes the view that meat sales are likely to benefit from a reduction in average fat levels, particularly in lamb. Total fat content is controlled by the mature size of the breed or strain and by the stage of maturity that has been reached. The balance between appetite (energy in) and maintenance requirement (energy lost) seems less important, although there are examples of lean genotypes with low appetites. The partitioning of total fat between carcass (particularly subcutaneous) and abdominal (particularly perirenal) sites is not influenced by mature size but rather by breed itself, especially in cattle. The reason may lie in intrinsic metabolic differences between subcutaneous and abdominal fat tissues. The number of fat cells in subcutaneous fat, but perhaps not in other fat deposits, increases as total fatness increases. Attempts to reduce eventual fat content by reducing the number of cells through underfeeding in early life have not been successful. Hormonal metabolism can be altered by injecting or implanting active constituents and sex hormone implants are presently available in some countries which aim to confer on females or castrated males the advantages (in terms of low fat and high lean deposition) of the entire male. However their effectiveness in reducing fat content is less than in increasing overall growth. Immunological techniques of growth control are being developed which leave no residues in meat and it is likely that the future will see increasing use of these and other approaches as farmers strive to meet consumers' requirements for lean meat at even lower production costs.

BB, Chrystall

Proceedings of the New Zealand Society of Animal Production, Volume 42, , 103-106, 1982