Genetic parameters for resistance to Aeromonas hydrophila in the Neotropical fish pacu (Piaractus mesopotamicus)

Abstract

Pacu (Piaractus mesopotamicus) is one of the main farmed freshwater fish species of South America. Disease outbreaks caused by Aeromonas hydrophila are considered one of the major bottlenecks for the development of pacu production. Genetic selection for disease resistance may represent a sustainable and effective alternative to reduce mortality and, therefore, improve productive performance of pacu. To verify whether A. hydrophila resistance can be included in genetic selection programs, the estimation of genetic parameters is needed. The aim of this study was to estimate variance components and heritability for A. hydrophila resistance in pacu, through experimental challenge performed in 36 full-sib families, resulting in the analysis of 1094 individuals. During 14 days of challenge, survival rate (TS) and time of death (TD) of fish presenting clinical signs of A. hydrophila infection were recorded. No influence of weight on TS or TD was detected. Genetic data were analyzed with two different univariate animal models using TS and TD. The total cumulative TS varied considerably among families (0 to 65.5%), which indicated a significant phenotypic variation related to resistance to A. hydrophila infection. TD ranged from 313 to 14,846 min, with an average of 1722 ± 1476 min. Low values for heritability were found for TS and TD (0.15 ± 0.05 and 0.12 ± 0.05, respectively). Our results represent the first report of genetic parameters for disease resistance in a Neotropical fish species and indicate that resistance against A. hydrophila in pacu might be improved through selection breeding.