Estimation of disease resistance and growth in F₅ generation families of GIFT tilapia

To assess the effects of selective breeding in GIFT tilapia (Oreochromis niloticus), we measured the disease resistance and growth performance of 42 families of GIFT tilapia F₅ generation, taking F₀ generation and hybrid tilapia (Oreochromis aureus×O.niloticus) as control groups. The results show that the survival rates of 36 families of F₅ generation were higher than that of F₀ generation, and the survival rates of 22 families were higher than that of hybrid tilapia after Streptococcus agalactiae infection. The disease-resistant breeding value was – 0.158 – 0.086 among different families. The absolute growth rates of 27 families were higher than that of F₀ generation. The correlation coefficient between the survival rate and the body mass was negative, and the quantitative value was – 0.033. According to the comprehensive comparison among the survival rate, disease-resistant breeding value and absolute growth rate for 42 families of F₅ generation, we have screened seven families (2^#, 3^#, 4^#, 6^#, 28^#, 31^#, 35^#) which were best-performing and can be used as breeding parents of F₆ generation. The results indicate that the disease resistance and growth performance of GIFT tilapia were improved significantly after five generations' selective breeding.