Dickerson (1970) stated that the performance criteria used for evaluating the efficiency of milk production could be improved upon. He argued that including estimated energy intake in the selection objective would dampen the enthusiasm for the larger cow per se and thereby reducing costs associated with cow maintenance. Almost 30 years later, a large number of traits are evaluated in dairy cattle populations including: milk production, survival, linear conformation traits and to a lesser extent fertility, health and liveweight traits. Most countries provide indices based on gross milk income as well as separate indices including conformation traits (Leitch 1994). The majority of the indices do not include the feed costs associated with increased production of the individual milk components from genetic improvement. Furthermore, exclusion of other major components of net income such as feed requirements for maintenance can favor higher producing larger cattle over comparatively lower producing, smaller cattle (Visscher et al. 1994) rather than cattle which maybe more economically efficient. In a pasture based system the objective is maximise the net income per hectare or more explicitly maximise the net income per unit of feed consumed, thus the first definition of efficiency is applicable.

B. L Harris

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 25: Lactation; growth and efficiency; meat quality; role of exotic breeds in the tropics; design of village breeding programs; n, , 383–386, 1998
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