Ovarian activity, transuterine embryo migration and prenatal losses in Ethiopian highland ewes

• Published in: Tropical animal health and production Vol. 39; no. 2; pp. 131 - 139
• Main Authors: Regassa, F, Tamrat, H, Bekana, M
• Format: Journal Article
• Language: English
• Published: United States Dordrecht : Kluwer Academic Publishers 01.02.2007; Springer Nature B.V
• Subjects: Abortion, Veterinary - epidemiology; Animals; Breeding; Corpus Luteum - physiology; Dry season; Embryo migration; Embryos; Ethiopia; ewes; Female; Gestational Age; Litter Size; Ovarian activity; Ovarian Follicle - physiology; Ovary - anatomy & histology; Ovary - physiology; Ovulation - physiology; Pregnancy; Prenatal loss; Rain; Rainy season; Season; Seasonal variations; Seasons; Sheep - physiology; Ethiopia
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-007-4355-6

A study was conducted on 1442 Ethiopian highland ewes to determine the seasonality of ovarian activity, intrauterine embryo migration and prenatal reproductive wastage. Assessment of ovarian follicular activity revealed that a higher (p < 0.01) proportion of ewes ovulated in the dry season than in the heavy and light rainy seasons. However, there was a tendency (p = 0.057) of decline in the mean number of ovulations per ewes during the light rains. The mean diameter of the largest follicle on the ipsilateral ovary was higher (p < 0.01) in both ewes with single and those with twin corpora lutea (CL) than on the contralateral ovary; and, compared to ewes with single CL, it was higher (p < 0.05) in those with twin CL. The right ovary was more active (p < 0.001) only in single-ovulating ewes. Similarly, a higher (p < 0.001) proportion of ewes were pregnant in the right horn. Embryos migrated to the opposite horn in single-, twin- and triple-ovulating ewes. There was a higher (p < 0.001) tendency for the left-to-right migration than the opposite. There was significant (p < 0.01) association between embryo loss and site and number of ovulations. Embryo loss was higher (p < 0.01) in ewes with twin ovulations on the right ovary. It is very likely that these results indicate a better chance of embryo survival in the right uterine horn.