Feed intake in channel catfish: is there a genetic component?

Increasing catfish growth is a primary objective of our broodstock improvement programme, and growth is at least partly dependent on voluntary feed intake. Two experiments were conducted to determine the genetic component of feed intake, and the relationship between feed intake and growth in sib-groups of channel catfish. In the first experiment, 10 fish from each of 31 full-sib families from the USDA-103 strain of channel catfish, Ictalurus punctatus (Rafinesque), were individually identified with passive integrated transponder (PIT) tags and distributed into two replicate tanks, five fish from each family to each tank. Fish were fed to apparent satiation with feed labelled with an X-ray opaque marker for one meal, radiographed, and feed intake was quantified for each individual. Genetic effects (broad sense heritability) accounted for approximately 41% of the phenotypic variation in feed intake. These fish were then grown for 5 months and the mean change in weight of the family groups was significantly correlated with mean feed intake (r = 0,64, P < 0.001). A subsequent experiment compared the feed intake of 100 families of catfish with their growth rate over the previous 2 months. Each family was grown in a separate 800 L tank. Fish were fed to apparent satiation daily and mean weight was determined monthly. After the 2 month growth period, fish were fed the labelled feed to apparent satiation, 28-30 individuals from each family/tank were radiographed, and individual feed intake was determined. A highly significant correlation (r = 0.54, P < 0,0001) between mean specific growth rate and mean feed intake (% consumption) was demonstrated. Taken together, these results suggest that individual feed intake has a heritable basis, and should be responsive to selection. Selection for increased feed intake could result in a correlated response of increased growth.