Effect Of A Fatty Acid Supplement On The Estrus Cycle And Pregnancy Rates Of Brazilian Pony Mares

The objective of this trial was to investigate the effect of a supplement rich in long-chain fatty acids on the reproductive performance in order to anticipate the onset of the cyclic season of mares. Twenty adult anestrous Brazilian pony mares aged between 4 and 10 years were used. Mares were examined for reproductive soundness and divided in two groups of ten mares with similar body condition (BC) in August. Group 1 received 50 mL of a rice oil commercial supplement, rich in gamma-oryzanol, oleic and linoleic acid, and group 2 (control) received 100 g sucrose diluted in 100 mL water. Both treatments resulted in 400 kcal daily. The mares were examined daily by rectal palpation and ultrasonography. Mares in estrous and with a dominant follicle (> 30 mm) were bred with a stallion of proven fertility every other day until ovulation (day 0). Reproductive tract examinations restarted on day 6 post-ovulation until the day an embryonic vesicle was detected and from this day on until day 60 of pregnancy. BC was evaluated again in November and in January. Analyzed parameters were: number of days from the beginning of the treatments to the first ovulation of the season (T-Ov); diameter of the first ovulatory follicle of the season (mm), diameter (mm) and area (cm2) on day 0 of the corpus hemorrhagicum (CH) and on day 6 of the corpus luteum (CL), circulating progesterone (ng/dl), percentage of mares cycling in January, pregnancy rates, and BC. No differences were observed among treatments in T-Ov (P = 0.37), diameter of the first ovulatory follicle of the season (P = 0.19), CH diameter (P = 0.23), CH area (P = 0.11), CL diameter (P = 0.19), CL area (P = 0.70), circulating progesterone (P = 0.31), percentage of mares cycling (P = 0.47) and pregnancy rates (P = 0.76). It was concluded that a rice oil supplement was not effective to anticipate the onset of the cyclic season.