@conference {40627,
	title = {The stock unit system - fair treatment for the breeding cow?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {319-322},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The stock unit (SU) system has been widely used in conjunction with  
gross margin (GM) and analysis to make recommendations to farm managers  
on the comparative profitability of pastoral livestock systems.  This information  
can be misleading, particularly where beef breeding cow policies are being  
compared with finishing cattle policies that involve high rates of liveweight  
gain (e.g. bull beef production).  To illustrate the deficiencies of the SU system  
for standardising between different livestock enterprises, relative gross margins  
per stock unit (RGM/SU) were derived for two case study farms in contrasting  
environments.  One property was located in the Manawatu region (Tuapaka),  
the other at Port Waikato (Limestone Downs) in South Auckland.  Using the  
breeding cow as a base (=100), the RGM/SU at Limestone Downs for breeding  
ewes, bull beef, steer finishing and once bred heifers were 70, 158, 74 and 121,  
respectively.  If these RGMIsu were expressed in terms of returns per kilogram  
of pasture consumed ($/kg) the rankings, relative to breeding cows (=100),  
were breeding ewes (51), bull beef (95), steer finishing (53) and once bred  
heifers (106).  Corresponding values for breeding ewes and bull beef at  
Tuapaka were 59 and 65.  Thus, the substitution rates between livestock  
enterprises varied substantially depending on the method used to account for  
differences in feed consumption.  The implications of these findings for farm  
management decision making are discussed. 
 },
	issn = {1176-5283},
	author = {Crawford HK and Lowe KI}
}
