Ovarian Activity During Normal and Abnormal Length Estrous CyCles in the Goat

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Abstract
Ovarian and behavioral cyclicity were studied during 3-5 estrous cycles in a group of 10 multiparous, Nubian does. Changes in ovarian morphology throughout the estrous cycle were identified and photographed laparoscopically. Estrous cycles (48) were observed during the study and of these, 21 were abnormally short in duration (mean .+-. SEM, 6.5 .+-. 0.5 days). Mean duration of the estrous cycle for the 27 normal length cycles was 21.5 .+-. 0.8 days. Eighteen of 21 (86%) of the short cycles and 6/27 (22%) of the normal cycles were initiated during early breeding season (between Sept. 1st and Oct. 15th). There were no differences (P > 0.05) in the duration of estrus for the short (mean, 2.9 .+-. 0.3 days) and normal (mean, 2.8 .+-. 0.8 days) cycle groups. A total of 6/11 (55%) of the short duration cycles examined laparoscopically appeared to be anovulatory, but ovulation was observed in all normal cycles examined. The number of corpora lutea (CL) observed during normal length and short estrous cycles was 3.1 .+-. 0.2 and 2.2 .+-. 0.2, respectively (P 0.01). The cumulative, percentage of does that showed morphological evidence of ovulation by the 1st, 2nd and 5th day after the onset of estrus was 30, 60 and 100%, respectively. Based on distinct differences in morphology and development, 2 types of CL were identified. The maximum visible diameter of type I and type II CL was 9.4 .+-. 0.6 mm and 5.1 .+-. 0.5 mm, respectively. Short estrous cycles observed early in the breeding season are associated with prematurely regressing CL or anovulation. The ovary apparently produces 2 morphologically distinct types of CL which differ not only in size and appearance, but also potentially in postovulatory function and longevity.