Feed conversion efficiency is an economically important trait in nearly all livestock production and improving feed conversion in farm-raised catfish through selective breeding would benefit producers. However, selection of improved feed conversion efficiency would require measuring feed intake in individual fish which is time consuming and not accurate. Weight loss during feed deprivation is correlated with feed conversion efficiency in several fish species, suggesting weight loss during feed deprivation could be used to indirectly select for improved feed conversion efficiency .
Trials were conducted to determine relationships among weight loss and feed conversion efficiency with Delta Select and Delta Control line channel catfish fingerlings. W eight loss was measured for 79 Delta Select line families and 20 Delta Control line families in replicate feed deprivation trials. Weight loss was higher for Delta Controls than Delta Selects . The 10 Delta Select families with the highest weight loss, 10 Delta Select families with the lowest weight loss, and 10 random Delta Control families were used in a feeding trial. I nitial weight, final weight, percent weight gain, and percent feed consumption were not different among Delta Select groups but were higher than the Delta Control. Feed conversion and survival were similar for all groups. Catfish from the feeding trial were used in a third feed deprivation trial. Family means for weight loss were positively correlated across all three feed deprivation trials but were not correlated with feed conversion indicating selection for weight-loss would not improve feed conversion. The percent of total variance associated with replicate family tank was much higher than the variance associated with family (~ 75% vs. 25%) for weight loss , FCR and RFI. Understanding the basis for the large replicate tank variance and reducing it through improved experimental design or accounting for it by statistical methods would improve assessment of feed conversion efficiency in channel catfish.
Results of this study indicate weight-loss during feed deprivation is not a good predictor of feed conversion efficiency in channel catfish. The faster growth of Delta Select catfish is primarily due to increased feed consumption. Studies to understand the basis for the large variance associated with replicate tank within family for weight-loss and feed conversion efficiency are currently being conducted.