Investigation of the effect of progesterone (Cue-MateTM) administration on ovulation induction in photostimulated anestrus mares

BACKGROUND: In mare, different methods of earlier cyclicity induction and hastening first ovulation of the year have been reported. OBJECTIVES: The goal of present study was to investigate the effect of progesterone (Cue-mate®) on synchronization and acceleration of the first ovulation of the year in winter anestrous mares under artificial lighting system. METHODS: After detection of anestrus mares, artificial lighting regimen of 16h light was conducted from early December for both treatment and control groups mares. After detecting of 25 mm follicle in the ovary, treatment group mares received Cue-Mate and examined were through rectal ultrasound until follicle reached the size of 35mm, when cue-mate was removed. Daily ultrasound examination and teasing were done until detection of ovulation. RESULTS: Based on our results, no significant difference in rate of ovulation (66% vs 60%) and size of ovulatory follicle existed between treatment and control group. In addition, despite of decreasing time interval of follicular growth from 25 mm to 35 mm (8.33±0.88 vs 10.75±2.28 in treatment and control groups respectively) and from each of these sizes to ovulation size, no significant difference existed between treatment and control groups. CONCLUSIONS: This was the first preliminary report of investigating the effect of progesterone plus artificial lighting on hastening first ovulation of the year in early winter anestrous. It seems more studies considering the greater number of mares in different ages are needed.