Ovarian activity in the mare between latitude 15 degrees and 22 degrees N.

Ovarian activity, as measured by the presence of small (10-15 mm diam.), medium (15-30 mm) and large (greater than 30 mm) follicles, corpora haemorrhagica and corpora lutea (CL), was determined in a total of 3584 ovaries during 1 year using post-mortem specimens. There were significant correlations of the incidence of ovulated follicles (ovulations), large and medium follicles (P less than 0 . 001) and of the mean number of small follicles (P less than 0 . 05) per mare with respect to season. The yearly averages of ovulated, large and medium follicles were 30 . 1, 13 . 9 and 73 . 9%, respectively, and the mean number of small follicles per mare was 2 . 0. The mean incidence of inactive ovaries throughout the year was 21 . 2%. The adjusted sinusoidal curves remained above their own yearly average from April to October (ovulations), March to September (large follicles), February to September (medium follicles) and January to July (small follicles), and below its yearly average from March to September (inactive ovaries). The mean incidence of multiple ovulations was 11 . 9%. No significant differences were found between the activities of the right and left ovaries. It was concluded that the mare shows a seasonal reproductive pattern near the equator in the northern tropical zone.