EFFECTS OF INJECTION OF GONADOTROPIN-RELEASING HORMONE ON SOW FERTILITY

Abstract

A total of 159 Landrace × Yorkshire sows were used to study the effects of an intramuscular injection of gonadotropin-releasing hormone (GnRH) at estrus on reproductive performance. Artificial insemination at 24 h or 24 and 40–44 h following treatment, resulted in similar conception rates for GnRH-treated (77.5 and 69.2%) and control sows (70.0 and 67.5%). Conception rates were not affected by insemination regime. GnRH treatment resulted in slightly improved litter sizes in comparison with control sows (10.45 vs 9.92; P > 0.20) whether inseminated once or twice, but had no effect on piglet weight at birth. Litter size and piglet weight at weaning were also not influenced by treatment. GnRH treatment (100 μg) induced increases in serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary within 30 min and maximal serum concentrations were observed 90–120 min postinjection. The induced release of both LH and FSH was of short duration (< 4 h), compared to the natural surge of LH which followed later, coincident with estrus. It was concluded that the overall reproductive performance of sows was not significantly influenced by GnRH treatment immediately prior to estrus. Key words: Sow, GnRH, pituitary response, reproductive performance