It is easy to achieve genetic change, but much more difficult to achieve genetic improvement.This study investigates the influence of selection on the cow efficiency in three landrace beef breeds (Afrikaner,Bonsmara,Nguni) in South Africa over a period of 25 years.Cow efficiency was defined as kilogram calf weaned (KgC) per cow Large Stock Unit (LSU). Breeding values for direct weaning weight in the Afrikaner and Bonsmara changed by +6.7kg and +11.7kg, respectively.That for mature cow weight only changed in the case of the Bonsmara (+9kg).The phenotypic changes were +21kg, +15kg and -14kg for weaning weight; and +14kg, +16kg and -22kg for mature cow weight in the Afrikaner, Bonsmara and Nguni, respectively.Cow efficiency increased by 12.0% in the Afrikaner and by 2.7% in the Bonsmara and decreased by 7.3% in the Nguni. Possible reasons for the differences between the breeds are discussed.

Frans J Jordaan, Michiel M Scholtz, Frederick WC Neser, Norman A Maiwashe, Zelda King

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Genetic Improvement Programs: Breeding objectives, economics of selection schemes, and advances in selection theory (Posters), , 391, 2014
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