Improving genetic selection for age at first oviposition in Cornu aspersum maximum snails using multiple-sire models

Different analysis models for age at first oviposition (AFO) were compared in a population of Cornu aspersum maximum snails kept under total confinement, aiming at recommending the most appropriate method for conducting the genetic evaluation of these animals. The snails were placed in mating boxes made up of dams from at least three different mothers, respecting a maximum age difference of 30 days between the dams in the same box. Single-trait analyses were carried out using an animal model and Bayesian inference, evaluating the phenotypes of 112 dams from a relationship matrix containing 3,007 individuals. Three different genetic evaluations were carried out: considering unknown paternity (1); assigning possible sires to the last generation of selection of each line (2); and assigning as possible sires the maximum number of ten sires per mating box (3); the last two applying multiple sire models. All the Markov chains converged according to the Heidelberger and Welch test. The Spearman correlations of the breeding values ranged from 0.75 to 0.96, suggesting changes in ranking when multiple sires were used in the analysis. Model 2 showed the best fit for age at first oviposition and is therefore recommended for conducting the genetic evaluation of animals under uncertain paternity for AFO in this population, to increase the reproductive precocity of the animals.