Abstract:
Follicular dynamics were studied during 12 interovulatory intervals (IOIs) and 36 preovulatory periods in Miniature mares. The percentage of IOIs with the following follicle events was: ovulatory wave with only one follicle ?10 mm (55%), diameter deviation similar to previous reports in larger mares (25%) and minor waves emerging before or after the ovulatory wave (55%). Follicle data were compared among Miniature ponies, large ponies and Breton horses (n = 12 IOIs per breed). The IOI was longer (P < 0.001) in Miniature ponies (23.3 � 0.9 days) and in large ponies (23.9 � 0.5 days) than in Breton horses (20.3 � 0.7 days). The Miniature ponies had fewer (P < 0.0001) growing follicles ?10 mm per ovulatory wave (1.5 � 0.3) and more (P < 0.0004) ovulatory waves (6/11) with only one follicle ?10 mm than large ponies (9.8 � 0.8 and 0/12) and horses (5.8 � 0.9 and 0/12). Maximum diameter of the preovulatory follicle was smaller (P < 0.003) in the Miniature ponies (38.3 � 0.7 mm) than in the horses (44.5 � 1.4 mm), but the difference between breeds was slight (6%) compared with the difference in bodyweight (65%). Considering the small number of follicles per ovulatory wave, Miniature mares are a potential model for comparative studies in folliculogenesis within and among species.