Female Seasonality - Donkey

Ovarian activity in the jenny starts between 8 and 24 months of age. This great variability can be explained by factors such as breed, nutrition, health, temperature and photoperiod. Seasonality of ovarian activity is variable and is likely to be influenced by photoperiod as well as nutrition and temperature. Scientific studies regarding seasonality present some discrepancy.

Jennies may cycle all year around in the southern USA. In Wisconsin (latitude 43°N), the seasonality of the jenny seems to be less pronounced than that of mares. At this latitude, 64% of females were found to be cycling in December. Seasonal anoestrus lasts between 39 to 72 days (Ginther et al, 1987).

A marked seasonality in which 54% of the females present an anoestrus has been reported in Brazil (latitude 19°51' 06"S). Anoestrus season lasts 166.3 ± 63.2 days (Henry et al ,1987). Seasonality has also been described in Mexico (Orozco Hernandez et al, 1992). In Morocco, our field observations show that the peak birthing season is March through May with some sporadic births occurring in February and from June until September. Studies in Ethiopia show that the rainy season (i.e. increased food availability) is associated with higher sexual activity, follicular growth and incidence of ovulation in free-ranging tropical jennies (Lemma et al, 2006a). Ovarian activity in these jennies is highly correlated with body condition (Lemma et al, 2006b).

References

• Tibary, A., Sghiri, A. & Bakkoury, M. (2008) Reproduction In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) The Professional Handbook of the Donkey, 4th edition, Whittet Books, Chapter 17

• Ginther, O.J., Scrabam, S.T., and Bergfelt, D.R. (1987). ‘Reproductive seasonality of the jenny’. Theriogenology 27. pp 587-592.
• Henry, M., Figueiredo, A.E.F., Palhares, M.S., and Coryn, M. (1987). ‘Clinical and endocrine aspects of the estrous cycle in donkeys (Equus asinus)’. Journal of Reproduction and Fertility Suppl.35. pp 297-303.
• Lemma, A., Bekana, M., Schwartz, H.J., and Hildebrant, T. (2006). ‘Ultrasonographic study of ovarian activities in the tropical jenny during the seasons of high and low sexual activity’. Journal of Equine Veterinary Science 26. pp 18-22.
• Lemma, A., Bekana, M. , Schwartz, H.J., and Hildebrant, T. (2006) ‘The effect of body condition on ovarian activity of free ranging tropical jennies (Equus asinus)’. Journal of Veterinary Medicine Series A- Physiology and Pathology Clinical Medicine 53. pp 1-4.
• Orozco Hernandez, J.L., Escobar Medina, F.J., and De La Colina Flores, F. (1992). ‘Ovarian activity in the mare and the female donkey during days with less light’. Veterinaria Mexico 23. pp 47-50.

FEMALE REPRODUCTION - DONKEY

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