FOLLICULAR GROWTH DYNAMICS IN MARES OF THE NORDESTINO HORSE BREED

The history of the Northeastern Horse, like that of other equine breeds, is closely linked to the colonization of Brazil. This species exhibits recurrent estrus in regions near the equator. Therefore, ultrasonographic evaluation of the ovaries allows for the determination of the number, location, size, and shape of ovarian follicles. In this context, the objective of this study was to evaluate the dynamics of follicular growth in Northeastern Horse mares following administration of a drug with luteolytic action. The research was conducted at Fazenda Faveira, in the municipality of Elesbão Veloso, Piauí State, using fifteen animals over a period of 22 consecutive days. The animals received two intramuscular doses (6.71 mg each) of dinoprost tromethamine, 12 days apart, for follicular growth synchronization. Forty-eight hours after the second dose, they were examined daily using a Mindray® Z6 VET ultrasound. Follicular growth monitoring considered a maximum of three follicles per ovary. Statistical analysis was performed using IBM SPSS Statistics software, version 26.0. Comparison of follicular diameters in animals that ovulated revealed no significant differences. Of the 15 animals, 66.66% exhibited follicular growth and ovulation, with an average daily follicular growth rate of 2.12 millimeters (mm). However, 33.33% did not show sufficient follicular development to reach ovulation. Northeastern Horse mares had an average follicular diameter of 37.11 mm one day before ovulation. In conclusion, the follicular growth dynamics observed in Northeastern Horse mares in this study are similar to those reported for mares of other breeds.