Fixed-time insemination with frozen semen in mares: is it suitable for poorly fertile stallions?

The research explores the suitability of two different protocols for inseminating mares with frozen semen: postovulation insemination and fixed-time insemination. It assesses fertility outcomes for both methods and whether they work similarly with highly or poorly fertile stallions, indicating that fixed-time insemination can be a useful method for both.

Objective of the Study

• The primary aim was to compare two protocols for equine frozen semen insemination: postovulation insemination and fixed-time insemination.
• The secondary aim was to assess each method’s efficiency and efficacy when using semen from stallions with different fertility levels- highly fertile and poorly fertile.
• The study wanted to evaluate pregnancy rates and intrauterine fluid (IUF) accumulation after artificial insemination using these procedures.

Methods and Procedures

• Six ejaculates were taken from two stallions processed, leading to twelve samples.
• The semen samples went through thorough evaluation via computerized semen analysis after thawing.
• The experiment involved inseminating fifteen mares (across 30 cycles) with frozen semen from a highly fertile stallion called “A”, and fourteen mares (across 28 cycles) with frozen semen from a poorly fertile stallion named “B”.
• Ovulation was artificially induced in the mares via the administration of deslorelin acetate after a follicle larger than 35 mm and uterine edema were observed.

Details of Postovulation and Fixed-Time Insemination Protocols

• In the postovulation insemination group, each mare was inseminated once with 800 × 10(6) total sperm within a maximum of 6 hours after ovulation.
• In the fixed-time group, each mare was inseminated twice with 400 × 10(6) total sperm: first at 24 hours, and then at 40 hours after ovulation induction.

Observations and Results

• After the procedure, mares were examined through ultrasonography to check for IUF accumulation 24 hours post-insemination and to diagnose pregnancy 14 days post-insemination.
• The accumulation of IUF was more noticeable in the mares who underwent postovulation insemination.
• However, the pregnancy rates were found to be similar regardless of the insemination method – postovulation or fixed-time. Only the fertility of the stallion had a significant effect on the outcome.

Conclusion of the Study

• The outcomes of the study suggested that fixed-time inseminations could be employed for both highly and poorly fertile stallions.
• This suggests that it can be a practical tool to facilitate more widespread use of frozen semen in equine reproduction programs.