Effects of Puberty and First Insemination Parameters on Lifetime Reproductive Performance in Replacement Gilts

This study investigated the influence of age, body weight, and backfat thickness at puberty and first insemination on the reproductive performance and retention rate across multiple parities in replacement gilts. A total of 3025 DanBred gilts were classified according to these factors. Their reproductive performance and survival were monitored up to the fifth parity. The estrus detection rate was 88.36%, and the success rate of insemination was 87.63%. Retention rates from the first to the fifth parity were 85.10%, 73.82%, 59.37%, 47.42%, and 36.36%, respectively. Multiple regression analysis further revealed that age at puberty was negatively associated with total born, born alive, healthy piglets, and weaned piglets across five parities (p < 0.01), while backfat thickness at puberty and first insemination showed consistent positive associations with these reproductive outcomes (p < 0.05). Gilts that reached puberty between 190 and 199 days of age had the highest total number of piglets born and weaned across five parities, whereas a delay in puberty onset significantly decreased the fifth-parity retention rate. Gilts with a backfat thickness > 15 mm at puberty exhibited the best reproductive performance, with a retention rate of 40.18%. For first insemination, gilts mated at 210-219 days (second estrus) produced more piglets, including more healthy piglets, across five parities, but delayed insemination age reduced the fifth-parity retention rate. Gilts mated at a body weight ≥ 140 kg showed better litter size performance, and those with a backfat thickness > 16 mm at first insemination had the greatest total number of piglets born and weaned. These results emphasize that optimal puberty and insemination parameters enhance long-term reproductive performance and retention in replacement gilts.