ORIGINAL RESEARCH Ultrasonographic studies on ovarian dynamics and associated estrus manifestations of jennies under controlled management, Ethiopia Hassen Kebede & Alemayehu Lemma & Haileleul Negussie Accepted: 3 May 2012 / Published online: 13 May 2012 Abstract A serial ultrasonographic study was conducted on nine jennies aged 5–15 years from January to April 2008 with the objective of studying ovarian follicular dynamics and estrus manifestations under controlled management. Ovarian follicu- lar activity was determined from the number and size distribu- tion of follicles, length of interovulatory interval (IOI), 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± 2.3 (range, 1–16) with sizes ranging from 2.9 to 44 mm. 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 preovu- latory follicles at -1 day before ovulation was 36.81±3.78 mm. The mean (±SD) IOI, estrus, and estrous cycle length were 25.4 ±3.6, 7.9±2.9, and 24.2±7.4 days, respectively. The mean (±SD) growth rate of the preovulatory follicle after the day of divergence was 1.9±0.3 mm/day. Serum progesterone profile followed the same patterns of ovarian dynamics with maximum values being detected during midluteal phase. Serum proges- terone assay revealed blood progesterone profiles of <1.0 ng/ml during estrus and up to 11 ng/ml during midluteal phase with a pattern following follicular dynamics. Body condition of the study jennies steadily increased and was positively correlated (r 0 0.52, p <0.001) with the diameter of the preovulatory folli- cle. In conclusion, the ultrasonic evaluation has revealed that follicular dynamics of jennies were generally related with body condition which might have been influenced by the type of management. Keywords Body condition . Estrous cycle . Jennies . Ovarian follicular activity . Ultrasonography Introduction Ethiopia, with an estimated 5.2 million heads, owns one of the largest donkey populations only next to China (Starkey and Starkey 2000). The per capita distribution is 27 donkeys for every 100 people (CSA 2010), which is one of the highest ratios in the world. Although they have wide- ranging roles in the national economy, donkeys are still among the most neglected species of domestic livestock with little or no interference in improving their productivity through breeding and health management. Subsequently, little or no complaints have been raised against their repro- ductive failures compared to cattle where management par- ticularly relating to poor nutrition is known to cause great economic losses. Numerous unpublished documentations confirm that in almost all cases donkeys in Ethiopia are left to forage for themselves when not working and nutritional management is at its lowest. As often constrained by the prevailing traditional management system, objective studies on the influence of management system on reproductive performance of donkeys are generally limited. On the other hand, the influence of nutritional status, as measured from body condition, on the ovarian activity is getting more attention both in mares (Fitzgerald and McManus 2000; Godoi et al. 2002; Guillaume et al. 2002) and jennies (Lemma et al. 2006a). Future implementation of controlled breeding or inter- vention schemes on genetic improvement necessitates the H. Kebede Faculty of Veterinary Medicine, Gondar University, P.O. Box 196, Gondar, Ethiopia A. Lemma : H. Negussie (*) School of Veterinary Medicine, Addis Ababa University, P.O. Box 34, Debre Zeit, Ethiopia e-mail: haileleul2011@yahoo.com Trop Anim Health Prod (2012) 44:1965–1970 DOI 10.1007/s11250-012-0165-6 # Springer Science+Business Media B.V. 2012