Abstract
Genetic progress in litter size in pigs have significantly increased in recent decades, resulting in a corresponding rise in farrowing duration (FRD). Prolonged FRD is negatively correlated with stillbirth rates and the colostrum intake of liveborn piglets. However, measuring FRD is time-consuming and, as a result, often unavailable. Consequently, studies exploring the genetic aspects of FRD in pigs remain scarce. The objectives of this study were to estimate the genetic parameters and prediction accuracy for FRD using phenotypic and genotypic data from a large commercial farm. Data were collected from 18,180 litters of 4,967 purebred Large White sows on a single farm in Brazil, between 2020 and 2024, as part of the farm’s routine data collection protocol. The time of birth was recorded at the piglet level, and FRD was recorded at the sow level, defined as the time between the birth of the first and last piglet in a given litter. All sows were genotyped using a custom Illumina 25K SNP chip. Genetic parameters were estimated using an additive linear model with ASReml v3. The model included fixed effects for population mean, litter type (purebred/crossbred), farrowing room, year-week, sow parity, average birth weight of piglets, and litter size. Random effects for permanent environment, additive genetic, and residual effects were also included. Gilts that had their first litter in 2024 were used as the validation set for prediction accuracy analysis. The correlation between their estimated breeding values using the entire dataset (“true breeding value”) during the genetic parameter analyses and their predicted genomic breeding values using only phenotypes collected before 2024 (“predicted breeding values”) was defined as prediction accuracy. The average FRD and litter size for sows in this dataset were 216±110 minutes and 15.0±2.7 piglets (total born), respectively. Results indicated that the population mean, year-week, sow parity, and litter size all significantly affected FRD (P < 0.001). The heritability of FRD was estimated at 0.07±0.01, with the permanent environment effect accounting for 0.03±0.01 of the total phenotypic variance. A clear, linear relationship between litter size and FRD was also observed. The prediction accuracy for FRD based on this dataset was 0.64. In conclusion, this study is the first to investigate the prediction accuracy of FRD in pigs using genomic data. Our findings suggest that while the heritability of FRD is low, the trait is heritable and can be genetically predicted, offering potential for improving FRD through genetic selection.