Effects of deslorelin or hCG administration on reproductive performance in first postpartum estrus mares.

The research investigates the impact of two drugs, deslorelin and hCG, on the reproductive performance of lactating mares after childbirth. The study finds that both substances can successfully induce ovulation, but deslorelin has certain side effects like delaying subsequent follicular growth and return to estrus, which might affect the mare’s chances of getting pregnant again.

Research Methodology

• The study involved 22 broodmares in southeast Texas. They were all administered either deslorelin, a synthetic hormone, or hCG, a hormone naturally produced in the body, to induce ovulation following their first postpartum estrus (heat cycle after giving birth).
• Mares were monitored daily for signs of estrus and examined twice weekly by transrectal ultrasonography.
• When a follicle of more than 35 mm diameter was identified, the mares were treated with either 2,500 U hCG intravenously or one implant (2.1 mg) deslorelin subcutaneously.
• Breeding was attempted every other day until ovulation was detected or until the mares ceased showing signs of estrus. Pregnancy check was done 16 days after treatment.

Research Findings

• Both hCG and deslorelin induced similar ovulatory responses and resulted in comparable pregnancy rates.
• However, mares treated with deslorelin had fewer ovarian follicles larger than 20 mm in diameter 16 days after ovulation compared to those treated with hCG.
• The interestrous intervals (the time between two heat cycles) were longer for mares treated with deslorelin that failed to conceive compared to the hCG-treated ones.
• The date of treatment was found to impact the length of the interestrous interval in deslorelin-treated mares but not in hCG-treated ones.
• All mares that failed to conceive from the initial breeding cycle after treatment did conceive from later breeding attempts. But for those treated with deslorelin, the interval from giving birth to successful conception was longer.