@conference {40630,
	title = {Biological efficiency: How relevant is this concept to beef cows in a mixed livestock, seasonal pasture supply context?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {333-336},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Efficiency, defined as the ratio of output to input, can be calculated for  
any product, and for any of the resources employed to generate that particular  
product.  "Weight of calf weaned per unit cow liveweight" is commonly used  
to measure biological efficiency in the beef cow herd, based partly on the  
assumption that feed intakes and hence costs are related to liveweight.  A more  
direct measure, and the one used here, is "weight of carcass produced per unit  
of feed intake".  The biological efficiency of the traditional beef breeding cow,  
determined in this manner, is low compared to that of other beef cow systems  
(e.g. twinning cows, once-bred heifers).  This is primarily because of the  
relatively low reproductive rate in traditional cow herds and the high proportion  
of annual feed consumption used to maintain the breeding female and her  
replacements. 
 
A simple output/input ratio may not, however, be appropriate for the mixed  
sheep and cattle systems which are widely used in New Zealand.  For these  
systems, where a competitive or complementary relationship may exist between  
enterprises, a more complex efficiency ratio that contains elements of the  
whole farm system is likely to be more appropriate.  Furthermore, in a seasonal  
pasture production system, where the supply of feed is likely to limit  
production at certain times of the year, feed does not have fixed value.  Feed  
costs therefore become an important component of the efficiency equation.   
Utilisation by other livestock of a scarce resource (e.g. winter feed) is also  
likely to have an influence on the economic efficiency of the system.  For  
example, if biological efficiency is ignored then output (weight of calf weaned)  
may be increased simply by increasing cow size but with no consideration of  
the extra feed inputs necessary to maintain larger cows, or the pressure that  
additional feed requirements may place on other components of the system at  
particular times of the year. 
 
In this paper, the relevance of biological efficiency is explored by comparing  
both biological and economic efficiencies of four cattle systems - traditional  
beef cows, beef x dairy cows (with and without twinning) and once-bred  
heifers - alone and in mixed sheep and cattle policies.  We conclude that  
biological efficiency is a relevant concept, primarily because its components  
(carcass weigh and feed consumed) are also important determinants of  
economic efficiency.  However marked differences between systems in the  
value of the carcass produced and/or feed consumed can lead to a poor  
correlation between the efficiency ranking of systems by biological and  
economic criteria. },
	issn = {1176-5283},
	author = {Morris ST and Brookes IM and Parker WJ and McCutcheon SN}
}
