Experimental comparison between selection for residual feed consumption and feed conversion ratio in Tribolium
Campo, J.L. | Turrado, H.
SUMMARY: Selection for residual feed consumption based on genotypic regression (RE) was compared with selection for feed conversion ratio (RA) using two experiments of downward selection for feed efficiency in Tribolium castaneum. The first experiment was designed to decrease feed consumption: weight gain, with residual feed consumption being based on weight gain from 7 to 14 days and initial weight, whereas the second experiment was intended to decrease feed consumption: egg mass, with residual feed consumption being based on egg mass between 28 and 30 days and adult weight. There were four generations of selection with four replicates, and a selected proportion of 20%. For each replicate, an unselected control was produced. Responses observed for the feed conversion ratio differed significantly between lines (p < 0.05) in both experiments; the RE lines having the greatest responses. The superiority of residual feed consumption as a selection criterion also held when this trait was considered as the selection objective, with mean responses differing significantly between lines (p < 0.05). It is suggested that both traits describe similar aspects of feed efficiency. The selection criterion used in line RE was equivalent to a restricted selection index, as was expected. The observed responses in the RA line were less than expected, especially in experiment 1, confirming the problems that may appear when a ratio is used directly as a selection criterion. The realized heritability was greater in a RE line in both experiments, in agreement with the theoretical expectations. The results show that residual feed consumption based on genotypical regression was an efficient selection method with respect to efficiency of feed usage.
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