Resistance against infectious pancreatic necrosis exhibits significant genetic variation and is not genetically correlated with harvest weight in rainbow trout (Oncorhynchus mykiss)

Infectious pancreatic necrosis (IPN) is one of the most prevalent and economically important diseases in rainbow trout aquaculture (Oncorhynchus mykiss). Vaccines as a conventional control measure have shown variable results under production conditions. Genetic improvement for resistance to IPN represents an alternative for the prevention of disease outbreaks. The objective of the present work was to estimate the heritability and genetic correlation for IPN resistance and harvest weight (HW) in rainbow trout. To determine the genetic resistance to the IPN virus, a total of 2278 fingerlings from 58 full-sib families were used, which were challenged with IPN virus to induce the disease. Resistance refers to survival to the disease and was defined as the day of death of each fish. HW was also recorded in 13,241 genetically related individuals from the same population. For the genetic analysis we fitted a bivariate mixed linear model including HW and resistance to IPN as dependent variables; tank: year: sex as a fixed contemporary group and age at harvest as a covariate for HW; and final weight as a covariate for resistance to IPN. The animal effect was included as a random effect for both traits. A random effect associated with common environment was also included for HW. The estimated heritability for IPN resistance was 0.39 +/- 0.08 and 0.35 +/- 0.06 for HW. Genetic correlation between IPN and HW resistance was not significant (0.05 +/- 0.25). The results indicate that the heritability for both traits is moderately high in this population, and that there is no significant genetic correlation between them. The presence of significant genetic variation for both IPN and HW resistance and the absence of genetic correlation between both traits indicate the feasibility of improving them simultaneously by means of artificial selection.