Ovarian response in mares to prolonged treatment with exogenous equine pituitary gonadotrophins.

This research was conducted on twelve anoestrous mares to examine their ovarian response to prolong treatment with exogenous equine pituitary gonadotrophins. They were treated with various hormones and extracts, with two different methods of gonadotrophin treatment tested, to observe if an interruption in treatment was necessary for new follicular growth.

Study Design and Methodology

• The study worked with twelve anoestrous mares that were treated with a combination of 0.5 g allyl trembolone and 50 mg oestradiol benzoate using an intravaginal sponge for seven days.
• After this, the mares received daily intramuscular injections of 25 mg crude equine pituitary extract, with six mares also receiving 0.25 mg of porcine growth hormone.
• After this stage of treatment, all the mares were given a combined treatment of the pituitary extract and allyl trembolone, again with half receiving additional porcine growth hormone, and others without.
• This treatment was either continued uninterrupted or a success interrupting pause was provided seven days after the first ovulation. The purpose of assessing both methods was to determine if an interruption was necessary to stimulate a new follicular wave.
• The research study compared two periods, specifically Days 0-47 and Days 48-94, for an analysis of follicular growth.

Results of the Study

• The findings suggest no notable difference in ovarian response was observed between the two groups irrespective of their treatment method.
• However, it was noticed that the occurrence of a new follicular wave didn’t necessarily require an interruption in the gonadotrophin treatment.
• Interestingly, the brief pause or interruption in treatment seemed to lead to a more synchronised growth of follicles.
• Ovulation rate in the second wave was higher than in the first although it was found that interrupting the treatment had no significant effect on the ovulation rate in the second follicular wave.
• The mares that didn’t experience an interruption in treatment continued to receive daily injections and oral progestagen, which resulted in persistent corpora lutea.