Evaluating genotype by environment interaction for growth in response to dietary protein replacements in Asian seabass (Lates calcarifer Bloch, 1790)

The use of plant proteins to partially replace fishmeal in Asian seabass diets is increasing due to rising prices of aquafeeds. This study assessed the magnitude of the genotype-by-environment interaction (G × E) for protein replacements and growth to determine whether the development of diet-specific lines was needed in our selective breeding program. Approximately 1800,120-day-old juveniles (weight = 53.13 ± 14.39 g) were stocked in six cages, nested in each of two ponds at 150 fish per cage. They were fed one of two experimental diets, D1 or D2, which differed in animal and plant protein composition for nine months. Phenotypes for body weight (BW), total length (TL), average daily gain (ADG), and condition factor (K) were collected at both mid-evaluation (270 days) and harvest (390 days). Heritability and G × E for growth traits were estimated using both univariate for single environment analysis (SEA), and multi-environment trial (MET) models. ANOVA results indicated that the means for all traits were not significantly different ( P > 0.05) between groups at either time point. At 390 days, BW was 1395.35 ± 256.76 g for D1 and 1400.84 ± 236.97 g for D2 while TL (∼46.0 cm), K (∼1.4) and ADG (∼3.5 g/day) were similar between groups. The heritability estimates for BW, TL, and ADG at 270 and 390 days under D1 and D2 using both approaches were moderate to high (0.26−0.39). The genetic correlations of genomic estimated breeding values (GEBVs) for growth traits between diets ranged from 0.67 to 0.86 for SEA and 0.83 to 0.99 for MET analyses, suggesting weak G × E interactions that did not impact the ranking of breeding candidates in the current stock.