Vol. 9, Issue 11, Part F (2025)

A retrospective study was carried out to evaluate the influence of age, parity and breeding season Thoroughbred mares maintained at commercial Stud Farm, Karnataka, India, during the period 2015-2023. Records of 747 mares involving 1,213 breeding cycles were analysed for conception rate, services per conception (SPC), gestation length, pregnancy losses and incidence of post-breeding endometritis (PBE) in foal-heat and regular-heat cycles. The overall conception rate per cycle was 52.8% with a mean SPC of 1.9. Fertility declined progressively with age, 62.7% (4-7 yr), 55.9% (8-11 yr), 48.1% (12-19 yr) and 37.7% (>20 yr). Conception rates were higher in maiden mares (64%) and foaling mares (58%) compared to barren/slipped mares (49%). The overall foal-heat conception rate was 58.7%, which was lower than that of regular cycles (66.8%). Mean gestation length was 336.4±3.5 days. Early embryonic deaths (EED) and late fetal deaths (LFD) were 11.4% and 13.0%, respectively. The findings indicate that mare age, reproductive status and uterine health after natural service mainly influence conception under Indian conditions.