Abstract
Simple SummaryThis study evaluated the influence of mean ovarian follicle size and the season of weaning on the effectiveness of administering the GnRH agonist buserelin to synchronize ovulation in weaned sows. The results from 352 sows demonstrated that sows with small follicles (<0.5 cm in diameter) at treatment are poor responders, a condition more frequent among sows weaned in summer–autumn than in those weaned in winter–spring.The GnRH agonist buserelin (GnRH), used to synchronize ovulation in weaned sows, attains only 70–80% effectivity, owing to several reasons of ovarian origin. This study evaluated in particular whether mean ovarian follicle size at treatment and the season of weaning are among those influencing GnRH responsiveness. The experiment was carried out in a temperate-region farm with 352 sows of 1–6 parities weaned either in winter–spring (WS, 174 sows) or in summer–autumn (SA, 178 sows). The sows were randomized into two groups: GnRH (10 µg of buserelin acetate at 86 h after weaning, 172 sows) and control (180 sows). The ovaries were transrectally scanned from weaning to ovulation and the sows clustered according to their mean follicular size at treatment time: small (<0.5 cm in diameter), medium (0.5 to 0.64 cm) and large (0.65 to 1.09 cm). In total, 88.33% of the GnRH-treated sows ovulated, with 82% of them within the expected time window (120–132 h after weaning). In contrast, 95.45% of the unresponsive sows had small follicles at the time of treatment and were mostly weaned in SA (20.45%) than in WS (4.76%). In conclusion, the conspicuous presence of sows having small ovarian follicles at treatment time compromises the efficiency of the GnRH agonist buserelin to synchronize ovulation in weaned sows, which occurs more frequently in summer–autumn weaning.
Highlights
Artificial insemination (AI) is widely used in the swine industry, becoming an essential tool to improve production [1,2], yet still requiring improvements to be fully efficient [3]
The aim of this study was to evaluate how the size of ovarian follicles at the time of treatment influences the efficiency of the GnRH agonist buserelin to induce and synchronize ovulation in weaned sows
The percentage of weaned sows that ovulated at the expected time window after administration of buserelin was above 70%
Summary
Artificial insemination (AI) is widely used in the swine industry, becoming an essential tool to improve production [1,2], yet still requiring improvements to be fully efficient [3] In this context, the implementation of a single fixed-time AI without the need of detecting estrus instead of customary multiple AIs after estrus detection offers substantial benefits. In order to achieve the highest fertility outcomes, effective single fixed-time AI requires inseminating just before the expected ovulation time.
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