Follicular dynamics predict optimal insemination timing in Yorkshire, Duroc, and Landrace × Yorkshire gilts

Accurate characterization of estrus and ovulation is critical for effective artificial insemination (AI) in pigs, yet comparative data on ovulatory dynamics among Yorkshire, Duroc, and Landrace × Yorkshire gilts remain scarce. In this study, transabdominal ultrasound was used to monitor ovarian activity in these three genetic lines following altrenogest-based estrus synchronization. For each genetic line, gilts were monitored at 8-h intervals. Landrace × Yorkshire crossbred gilts exhibited a significantly shorter altrenogest-withdrawal-to-ovulation interval (P < 0.05). In the full cohorts (Yorkshire, n = 200; Duroc, n = 90; Landrace × Yorkshire, n = 504), Yorkshire gilts had the highest litter size, whereas Duroc gilts developed larger pre-ovulatory follicles (based on a subset of 17 gilts per breed) but had lower litter size. A negative correlation between estrus-onset timing and the estrus-to-ovulation interval was observed across all genetic lines. Farrowing rates exceeded 90% in all groups. These findings provide critical physiological data for designing breed-specific precision breeding strategies in commercial pig production.