A comparison of different predictors of the lean content of pig carcasses 2. Predictors for use in population studies and experiments

Abstract

Linear measurements and sample joint dissections were examined as predictors of carcass lean percentage using data from 1060 carcasses comprising 108 subgroups (nine genotypes × two sexes × two feeding regimes × three slaughter weights). The potential predictors were examined in terms of precision, cost and the stability of their regression equations.Probed fat thickness 6·5 cm from the dorsal mid-line at the last rib (P2) was the individual measurement giving the most precise prediction (residual s.d. pooled within subgroups = 2·21 percentage units; r = −0·72). The square root transformation (P2½) gave stable regression slopes over levels of all four factors, though there were important differences in intercepts between genotypes, sexes and slaughter weights.The precision of prediction from the lean percentage of sample joints was generally improved by including P2½ with each in multiple regression. Used in this way with current Meat and Livestock Commission costings, the ham joint offered the best compromise between cost and precision (pooled residual s.d. = 1·25 percentage units; R = 0·92). Regression slopes on each joint were stable for all factors except for those on the rump back and rib back joints which varied by feeding regime. Intercepts varied by genotypes for all joints except the ham, while intercept differences for feeding regimes were small or non-significant.The results confirm the value of the ‘sub-sampling with regression’ procedure for predicting carcass composition.

Correlations between indirect and direct measurements of body composition

“…https://doi.org/10.1079/PNS19860035 I 986 those based on White-bred populations. We have also found important differences in carcass lean content at equal fat thickness among pigs from different commercial breeding companies in Britain (Evans & Kempster, 1979) and have also suggested that relations can change significantly over time (Diestre & Kempster, 1985).…”

“…Equations can be constructed separately for each treatment or individual treatment intercepts can be used together with pooled within-treatment dopes as in the double-sampling-with-regression procedure (Conniffe & Moran, 1972;Evans & Kempster, 1979). The double-sampling technique can be used effectively and anyone considering carcass-evaluation techniques is recommended to explore its use.…”

The effect of animal types on a simple control method used in the calibration procedure for assessing lean content in pig carcasses

“…On the other hand, the animal type bias found in the relationships between the reference method and the on-line instrumental methods (e.g. fat and muscle thickness measurements) seems to be a more serious problem (Branscheid, Komender, Oster, Sack, & Fewson, 1987;Engel, Buist, Font i Furnols, & Lambooij, 2004;Evans & Kempster, 1979;Gu et al, 1992;Planella & Cook, 1991;Wood & Robinson, 1989;Zelenák et al, 2004).…”

Accuracy and consistency of prediction of pig carcass lean concentration from P2 fat thickness and sample joint dissection

“…The biasing effect of population, sex and feeding regimen on the prediction of carcass lean concentration from P2 and carcass weight were previously identified by Evans and Kempster (1979). These authors, in disagreement with the present data, found the prediction from P2 to be stable in Subcutaneous fat 5-2 Sex 0-7 1-4 2-1 6-6 2-8 3-0 6-0 Feeding 0-1 0-2 0-5 0-1 1-8 0-9 2-7 Population and sex 3-6 5-1 5-7 8-9 5-9 5-9 8-2 slope over pig populations.…”