Data on 630 crossbred lamb carcasses were used to estimate genetic parameters for a number of carcass measures, fitting a multivariate animal model using restricted maximum likelihood. Carcass measures included: cold carcass weight (CCW). EUROP conformation and fat class scores (MLC-CF), primal joint weights predicted using MLC-CF and several carcass linear and area measures obtained by Video Image Analysis (VIA-DM). Heritability estimates for subjective carcass traits (MLC-CF and primal joint weights predicted using MLC-CF) were low (0.05-0.17), whereas those for objective carcass traits (linear and area measurements on the carcass from VIA) were moderate to high (0.20-0.53). Phenotypic correlations between MLC-CF and VIA-DM were in general low (0.01-0.51) and genetic correlations were slightly higher (-0.04-0.81), when interpreting their absolute value. The results suggest that selection for shorter carcasses (VIA lengths) will be associated with improved conformation but a reduction of the total CCW. Likewise there was a trend in the genetic correlations between conformation and carcass widths which indicated that conformation could also be improved by selection for wider carcasses as measured by VIA which in turn will also imply an increase in CCW. The genetic correlations between VIA-DM and fat class score were only significantly different from zero for the VIA measurement for the leg area (r(g) = -0.73). Length traits were highly correlated with each other, with an average genetic correlation of 0.84. Positive genetic correlations (0.47-0.85) were found between widths measured on the shoulders and chest with hind leg widths. The areas measured on the carcass were moderately to highly correlated with each other (0.54-0.90). In general, genetic correlations which were found to be significant between areas, lengths and widths were moderate to high and positive. Phenotypic and genetic correlations along with heritabilities of the VIA-DM from crossbred lambs, suggest that using this VIA dimensional information in the evaluation of purebred terminal sire breeds is likely to improve conformation on crossbred lambs.
- Video Image Analysis
- Dimensional measurements