Heritability and Genotype-by-Environment Interaction for Harvest Weight of Nile Tilapia, Oreochromis niloticus, Fed with Fish Meal- and Non-Fish Meal-Based Diets.

While aquaculture of Nile tilapia Oreochromis niloticus is expanding worldwide, fish meal as a major protein source has become limited due to declining supply and environmental concerns. The aims of this research were to evaluate the magnitude of genotype-by-environment interaction (G×E) effect on harvest weight in commercial tilapia populations that were raised with fish meal-based and non-fish meal-based diets, and the impact of complete fish meal replacement on genetic parameters. Heritability estimates for body weight at harvest of Nile tilapia fed with fish meal and non-fish meal diets were based on data obtained from 120 full-sib and 50 half-sib families. A mixed linear animal model was used for data analyses, and variance components were estimated using an average information restricted maximum likelihood procedure. The heritability estimates for harvest weight (h2HW) of Nile tilapia fed with fish meal (0.23±0.03) and non-fish meal (0.22±0.03) diets were moderate. The correlation between family means of the estimated breeding values (EBV) for growth using fish meal and non-fish meal diets was 0.99, which implied no significant evidence for G×E. These genetic parameter estimates indicate good prospects for selective breeding to improve body weight at harvest for both fish groups fed fish meal and non-fish meal diets. Lack of G×E implied that each genotype was affected at a similar magnitude. Therefore, best fish selected for growth with fish meal diet would also perform well with non-fish meal diets. These results imply that changing from fish meal to non-fish meal diets would not affect the genetic improvement program for Nile tilapia. [ABSTRACT FROM AUTHOR]