Supplementation of boar semen extender with 5 μg of buserelin improves litter size and birth weight in gilts raised under tropical field conditions.

Administering exogenous GnRH at the onset of standing estrus induces ovulation within ∼37.5 ± 3.3 h by stimulating LH secretion, narrowing the optimal insemination window. This study evaluated the effects of supplementing extended boar semen with a GnRH analog (buserelin) for fixed-time AI on conception rate, farrowing rate, and litter size under tropical field conditions. A total of 741 French Landrace × Yorkshire females (319 gilts, 422 sows) were used across nine replicates. After estrus detection, females were randomly assigned to four groups: control (n = 191), 10-IM (n = 183; 10 μg buserelin i.m.), 5-S (n = 181; semen + 5 μg), and 10-S (n = 186; semen + 10 μg). Gilts were inseminated at 0, 12, and 24 h; sows at 12, 24, and 36 h post-estrus. Litter data were collected from 223 farrowings: control (29 gilts, 34 sows), 10-IM (16 gilts, 35 sows), 5-S (29 gilts, 25 sows), and 10-S (27 gilts, 28 sows). Across groups, average farrowing rate was 88.9 %, with total number of piglets born per litter (TB) 17.0 ± 4.0, number of piglets born alive per litter (BA) 15.2 ± 3.5, stillborn 1.0 ± 1.5, and mummified fetuses 0.5 ± 1.2. No significant differences in conception or farrowing rates were found. The 5-S group had a significantly higher litter weight than the control group (24.5 ± 2.0 kg vs. 19.4 ± 0.7 kg; P = 0.018). Gilts receiving 5 μg buserelin in semen had significantly higher TB, BA, and litter weight (P < 0.05), while 10 μg increased litter weight without affecting TB. In sows, no significant improvements were observed. These results suggest that supplementing semen with low-dose GnRH analog can improve gilt productivity under tropical conditions and merits further investigation.