Genetic parameters for the mean and phenotypic variability of litter size traits in native pig breeds: Złotnicka White and Złotnicka Spotted

Breeding native pig breeds holds surging international interest due to their role in biodiversity conservation. Regardless of the breed, the success of pig breeding is related to litter size. This trait is not only economically important but also essential for preserving the genetic resources of native breeds. Three Polish native pig breeds are maintained by genetic resource conservation programmes in Poland, with Złotnicka White and Złotnicka Spotted being the subjects of our study. Only one study has been conducted on the genetic parameters and heritability of litter size in these breeds. Moreover, the genetic parameters associated with the phenotypic variability of litter size traits have never been studied in these native pig breeds. Thus, this study aimed to estimate the genetic variance components and genetic correlations for the number of piglets born alive (NBA) and the number of piglets living at 21 days, as well as the phenotypic variability of these traits in populations of Polish Złotnicka White and Złotnicka Spotted native pig breeds. Phenotypic data revealed that despite the growing population of Złotnicka breeds, the litter size decreased, whereas the trait variation remained at the same level. The heritability of litter size traits in the Polish Złotnicka pigs reported in this study was lower than in other European native breeds and varied from 0.10 to 0.13. The heritability of variability for the studied traits was within the expected range (0.007–0.014). The low or moderate correlations between the mean NBA and its phenotypic variability (0.23 and 0.50) indicate that selection in the desired direction for the two traits would be possible. This was also confirmed in the simulation analysis. Złotnicka breeds have greater heritability of phenotypic variability than commercial breeds. The moderate correlations between the mean and variability of the litter size traits indicate that it would be possible to reduce variability without losses at the litter size level if an appropriate breeding programme were applied. This is not an easy task since genetic resource conservation programmes focus on preserving the population’s genetic variation rather than enhancing it. Thus, as the Złotnicka breeds are under conservation programmes, such selection might never be implemented. We also indicated that the variability of litter traits in native breeds resembles that reported in commercial pigs, even though it is lower. This can benefit breeding programmes of other native European pig breeds to help maintain the optimum litter size.