The stability of the relationship between subcutaneous fat percent in the rack and the side for Southdown ram carcasses


I.T. Kadim, R.W. Purchas, A.L. Rae and R.A. Barton

Animal Science Department, Massey University, Palmerston North

Proceedings of the New Zealand Society of Animal Production. 1988, 48: 29-32

Two experiments, involving a total 78 Southdown rams from high- and low- backfat lines, were carried out to examine the relationship between subcutaneous fat percent of a rack cut and subcutaneous fat percent of the whole carcass side.

A simple regression was as effective as multiple regressions for 30 carcasses (Group 1), but for each equation there was a significant selection-line effect on the intercept. When the usual direct regression coefficient was replaced by an inverse or a geometric co- efficient, the selection line effect was not significant.

The 3 prediction equations were evaluated by comparing predicted side subcutaneous fat percent with actual values for a separate lot of 48 ram carcasses (Group 2). The correlation between predicted and actual values was high, but the selection-line effect was significant for all 3 equations. These results serve to emphasis that even within a breed and sex, and for relations with high correlations, there may be problems with the stability of the prediction equations. This could introduce a bias into conclusions.

Keywords: NZSAPAB; Southdown; rack cut; subcutaneous fat; genetic line; sample cut


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Last Updated 18-03-1997