Negative genetic correlations between production traits and head or bony tissues in large all-female rainbow trout (Oncorhynchus mykiss)

Genetic parameters of production traits (growth, carcass yield, fillet yield) and bony tissues (head and vertebral axis) were estimated for large all-female rainbow trout Oncorhynchus mykiss reared in freshwater. Genetic parameters were estimated using REML at 16 months of age (1636 g) on 1962 DNA-assigned progenies from a partial factorial mating design with 60 dams and 100 sex-reversed sires. Most traits presented medium to high heritability (0.37 to 0.54). A high genetic correlation (r(A)=0.97) was found between fillet yield and headless gutted carcass yield (or HGCarc%). Due to its higher heritability and high genetic correlation with fillet yield, selection on HGCarc% should result in a 50% increase in selection efficiency on fillet yield by reducing operator-linked variability at filleting. However, strong negative genetic correlations were estimated between body weight or fillet yield and bony tissue development as head yield or the head and vertebral column yield (-0.48 to -0.57). Ten generations of selection on body weight (or fillet yield) are, therefore, predicted to decrease the relative head development by 25 to 30% for slaughtering at constant age. As it is impossible to disentangle this result from a correlation that is only mathematically determined, this result needs further investigations. If yields are corrected according to their allometric relationship with body weight, only selection for fillet yield will decrease the proportion of bony tissues for a slaughtering at a constant body weight. Whatever the final objective of selection (to increase body weight or to shorten the production cycle at constant body weight), it is concluded that at least selection on fillet yield will affect the relative head and the vertebral axis development and that selection on growth may affect bony tissue development. These results are discussed in relation to the past results from livestock breeding, resource energy allocation theory and a future improvement of robustness by selection. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.