Effects of sex, family, and size grading on feed conversion ratio, growth, visceral fat, and weight loss in Delta Select channel catfish

Abstract Feed conversion efficiency (FCE) is an important determinant of profitability in catfish production. Understanding factors affecting FCE at a physiological level could lead to improvement of FCE at production scale. The effect of sex, family, and size grading within family on juvenile channel catfish (Ictalurus punctatus) growth, feed consumption, feed conversion, visceral fat accumulation, and weight loss during feed deprivation was determined. In Trial 1, fingerlings from five channel catfish families were graded by weight into small, large, and random mixed‐size groups, fed for 8 weeks, subjected to 2 weeks of feed deprivation, and then euthanized to determine sex. Family had a significant effect on fish growth, feed consumption, FCE, and percent weight loss during feed deprivation. Large fish had faster growth, better FCE, and lower percent weight gain than small fish from the same family. Mixed‐sized fish were generally intermediate for all measured traits. In Trial 2, all‐male, all‐female, and mixed‐sex groups of channel catfish fingerlings were subjected to the same feeding regime and then euthanized to confirm sex and weigh visceral fat. Males had a higher percent weight gain, better feed conversion, and less visceral fat than females; mixed‐sex fish were generally intermediate between all‐male and all‐female groups. FCE was positively correlated with visceral fat percentage in the all‐female treatment (i.e., fatter fish had poor feed conversion), but not in the all‐male treatment. Feed conversion and weight loss during feed deprivation were generally not correlated in either trial. This is the first report that male channel catfish convert feed more efficiently than females. Future studies should investigate the relationship between fat and feed conversion in channel catfish.