Comparative slaughter

Measuring energy retention by the comparative slaughter technique... 

Table 11.4 Use of the comparative slaughter technique to estimate the energy retention and heat production of poultry...

Energy retention may be estimated indirectly as ME intake minus heat production, or directly from the animal s carbon and nitrogen retention in a respiration chamber. It may also be measured using the comparative slaughter technique, where a known amount of ME is given and body composition is measured at the beginning and end of the experiment. 

Nitrogen balance is the difference between nitrogen intake and nitrogen output in the form of faeces, urine, milk and eggs. As an estimate of protein deposition in the animal s tissues, it is subject to several errors, and the results have been known to diverge from those of the comparative slaughter technique. 

In contrast to AERC (1993), where maintenance requirements are derived from calorimetric methods, the maintenance requirements of beef cattle published by NRC (2000) are derived using the comparative slaughter technique. This has the advantage of allowing experiments to be conducted under conditions more similar to those encountered in practice, and the effects of activity are implicitly incorporated. The NEjn requirement of beef cattle can be predicted from empty body weight (EBW) as follows ... 

It is interesting to note that the NE requirements of beef cattle derived using comparative slaughter techniques and adjusted by 20 per cent for dairy breeds are similar to those of dairy cows derived using calorimetric methods. The NE , requirement of sheep predicted by NRC (2007) of 0.23 is similar to that adopted by AFRC (1993). 

Garrett, W.N., 1980. Energy utilization by growing cattle as determined in 72 comparative slaughter experiments. In Proceedings of Energy Metabolism, 8, Cambridge. Butterworths Co 3-7. 

Lofgreen, G.R, 1965. A comparative slaughter technique for determining net energy values with beef cattle. In Proceedings of Energy Metabolism, 3, Troon. Academic Press 309-317. 

Steen, R.W.J., L.E.R. Dawson, D.E. Kirkpatrick, and S.D. Johnston, 1997. Estimation of maintenance energy requirements and efficiency of utilization of metabolizable energy for growth in lambs by indirect calorimetry and comparative slaughter. In McCracken, K., Unsworth, E.E, and A.R.G. Wylie (eds.). Energy metabolsim of farm animals. CAB Inbtemationa, Wallingford, UK 351-354. 

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