ULTRASONOGRAPHIC STUDIES ON OVARIAN DYNAMICS AND ASSOCIATED ESTRUS MANIFESTATIONS OF JENNIES UNDER CONTROLLED MANAGEMENT
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2008-06
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Abstract
Serial ultrasonographic study was conducted on nine Jennies aged 5-14 years from December 2007 to April, 2008 with the objective of characterizing ovarian follicular activities and estrus manifestations under controlled management. The jennies were housed, fed on hay and concentrate, regularly watered and were not working during the study. Ovarian follicular activity was determined from number and size distribution of follicles, length of interovulatory interval, growth rate of preovulatory follicles, diameter of follicles at the onset of estrus and incidence of ovulation. Estrus manifestations were characterized using length of estrus and estrous cycle. The mean (± SD) number of follicle detected per ovary was 5.45 ± 2.25(range 1 -16) with sizes ranging from 2.88mm to 44mm.The mean (± SD) size of follicle encountered at the onset of estrus was 25.9 ± 3.7 mm (range 20.9 – 34.4) while that of the preovulatory follicles at -1 day before ovulation was 36.81 ± 3.78mm. The mean (± SD) interovulatory interval, estrus and estrous cycle length were 25.4 ± 3.6; 7.85± 2.99 and 24.22 ± 7.43 days respectively. The mean (± SD) growth rate of the preovulatory follicle after day of divergence, which fell on -8 day before ovulation was 1.89 ±0.33mm/day (P<0.001). Follicles were known to grow in cohorts constituting two or more waves. Serum progesterone profile followed the same patterns of ovarian dynamics with peak values being detected during mid luteal phase. Serum progesterone assay revealed blood progesterone profiles of <1.0 ng /ml during estrus and up to 11ng /ml during mid - luteal phase which has shown the presence of ovarian cyclicity through out the study period with patterns following follicular dynamics. Majority (82.14%) of the estrus manifestations were significantly (p<0.005) associated with ovulations. Body condition was positively correlated (r = 0.52, P< 0.001) with the diameter of the preovulatory follicle and negatively with the number of follicles per ovary (p<0.01). Estrus length was also found to be positively correlated to size of preovulatory follicle at onset of estrus (r = 0.412, p<0.05) and negatively correlated to interovulatory interval (r = -0.548, p<0.05). Ovarian follicular dynamics in jennies are generally equine prototype with subtle differences. In contrast to previous reports of reproductive activity under traditional management systems, this study confirmed as improved management can also improve the ovarian activity. However, it still remains to be verified as to see the relative and individual effects of management factors on follicular activity.
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Estrous cycle, Jennies, ovarian follicular activity, ultrasonography, progesterone