Relationship between pharmacological induction of estrous and/or ovulation and twin pregnancy in the Thoroughbred mares.

The research article investigates the potential link between certain hormonal treatments used to induce ovulation in Thoroughbred mares and the prevalence of twin pregnancies. The findings suggest that horses receiving such treatments are significantly more likely to have twin pregnancies than those who do not.

Treatments and Control Group

• The study involved 680 Thoroughbred mares in total.
• 356 of these mares were administered one of three treatments designed to induce ovulation. These treatments were: cloprostenol upon the detection of a Corpus Luteum (CL) via ultrasound; human chorionic gonadotropin (hCG) immediately prior to mating; or a combination of the previous two treatments.
• The remaining 324 mares did not receive any form of treatment to induce ovulation and were assigned as the control group.

Comparison of Twinning Rates

• The study observed the rates of twin and single pregnancies in both treated and untreated mares.
• It was discovered that the rate of twin pregnancies in treated mares was significantly higher than in untreated mares. About 16.6% of treated mares had twins, compared to 6.5% of control mares.

Comparison Between Different Treatments

• The researchers further analyzed the relationship between the type of treatment and the occurrence of twins.
• Statistical significance was found when comparing mares treated with hCG alone to those given a combination of prostaglandin F2alpha (PGF2alpha) and hCG.
• Further, significant differences were also found when comparing each treatment group with the controls. The least difference was between the hCG treatment group and controls, the second was between mares given PGF2alpha and controls and the greatest difference was between those given the combined PGF2alpha and hCG treatment and the controls.

Conclusion

• The study concludes that pharmacological induction of ovulation in Thoroughbred mares may have a strong correlation with higher rates of twinning.
• These findings have important implications for breeders and vets, as twin pregnancies in horses can pose a significant threat to the health and wellbeing of both the mother and the twin foals.