Fillet Yield and Quality Traits As Selection Criteria for Nile Tilapia (Oreochromis niloticus) Breeding

Nile Tilapia breeding programs have been focused on growth improvement by selecting for either body weight (BW) or daily weight gain (DWG). Along with growth traits, yield and quality traits are also of great importance in livestock breeding. Our objective was to evaluate the feasibility of including fillet yield and quality traits as selection criteria for improving performance in Nile Tilapia. The fish used in this study came from a population of 3 generations undergoing selection (Aquaamerica Company, Brazil). Pedigree information was available for 5263 fish. Phenotypes for body weight at 290 days (BW290) and daily weight gain (DWG) were measured on 2585 males and females, fillet weight (FW) and fillet yield (FY) were measured on 1198 males, and fillet fat content (FAT) was measured on 1136 males. Variance components were estimated in single and two-trait models using GIBBS1f90 and the post-analyses were carried out using POSTGIBBSF90, both from BLUPF90 family of programs. For all analyses, spawning was considered as a random common environmental effect; harvest weight, weight at tagging and age were used as covariables for DWG and BW; body weight at slaughter was used as a covariable for FW, FY, and FAT; floating cage and sex were included as fixed effects for all traits and for BW290 and DWG, respectively. Heritability estimates for DWG, BW, and FW were close to 0.23, whereas FY had the highest heritability (0.32) and FAT had the lowest (0.20). Genetic correlations of DWG with FY and FAT were -0.09 and -0.4, respectively; BW290 with FY and FAT were -0.1 and -0.32, respectively. The only positive correlation was between FY and FAT (0.6). Negative correlations between growth and fillet traits indicate an increase in guts and carcass weight in bigger fish, which is not desirable. Based on the estimated heritabilities, the genetic improvement of fillet yield and quality traits can be effective and should be included in the selection criteria. These results are particularly important for FW and FY since there is a market interest on increasing fillet yield. In addition, fillet quality traits such as FAT are also of interest to enhance meat quality.