In this study, the objective was to investigate whether non-lethal methods, utilizing body measurements, could be used to efficiently predict fillet weight and genetic analysis for in a complete diallel cross of three Nile tilapia strains. As in females, early sexual maturation was widespread, only 958 male fish from 81 full-sib families were used, both for prediction of fillet traits and in genetic analysis. The prediction equations from body measurements were established by a forward regression analysis, choosing models with the least predicted residual error sums of squares (PRESS).
The results revealed that body measurements on live Nile tilapia is well suited to predict fillet weight, but not fillet yield (R2= 0.945 and 0.209, respectively), but both models were seemingly unbiased. The genetic analyses were carried out with bivariate, multibreed models. Body weight, fillet weight and predicted fillet weight were all estimated with a heritability ranged from 0.23 to 0.28, and with genetic correlations close to one. Contrary, fillet yield was only to a minor degree heritable (0.05), while predicted fillet yield obtained a heritability of 0.19, being a resultant of two body weight variables, known to have a high heritability. The latter trait was estimated with genetic correlations to body weight and fillet weight traits larger than 0.82.
No significant differences among strains were found for their additive genetic, reciprocal or heterosis effects, while total heterosis effects were estimated positive and significant (P < 0.05). As conclusion, prediction of prediction of fillet weight based on body measurements is possible, but not for fillet yield.