Embryo reduction before day 11 in mares with twin conceptuses.

The research article studied the incidence of natural elimination of twin embryos in mares before day 11. It also investigated the effects of unilateral and bilateral double ovulations on the incidence of embryo reduction.

Objective and Purpose

• The primary objective of the research was to study the incidence of natural elimination of one of the twin embryos in mares before day 11. This process is referred to as ’embryo reduction’.
• The researchers aimed to compare the number of ultrasound detected conceptuses per ovulation in single and double ovulating mares to uncover any possible link between the type of ovulation and incidence of embryo reduction.
• The secondary objective was to understand the effect of unilateral (one sided) and bilateral (both sided) double ovulations on the frequency of embryo reduction.

Methodology

• The research involved 50 double-ovulating mares and compared each with two single-ovulating mares. This led to a total of 100 ovulations or potential embryos for each group.
• The incidence of conceptus generation from an ovulation was inspected for single, bilateral double, and unilateral double ovulators.
• Expected frequencies of none, one, or two conceptuses in a mare with double ovulations were calculated based on the day 11 pregnancy rate of single ovulators (85%).

Results

• It was observed that the frequency with which an ovulation led to a conceptus was greater for single ovulators and bilateral double ovulators compared to unilateral double ovulators.
• For unilateral double ovulators, observed frequencies of none, one or two conceptuses differed significantly from the expected frequencies based on the pregnancy rate of single ovulators. This suggests the possibility of a higher incidence of embryo reduction in unilateral double ovulators.
• However, for bilateral ovulators, the results did not indicate a similar phenomenon. Each ovum had the same chance of developing into a day-11 conceptus as an ovum in single ovulators, suggesting no significant embryo reduction in this group.
• In case of unilateral double ovulators, the lower day-11 pregnancy rate per ovum compared with bilateral and single ovulators, could be attributed to a higher frequency of mares with no embryonic vesicles rather than a higher frequency of mares with one vesicle.

Conclusion

• The study provides insights into the impact of double ovulation on the incidence of embryo reduction in mares before day 11. This knowledge can have potential applications in the field of horse breeding and veterinary medicine.