Ovarian activity, transuterine embryo migration and prenatal losses in Ethiopian highland ewes.
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.
Regassa
F
F
Faculty of Veterinary Medicine, Debre-Zeit, Ethiopia. regassaf@yahoo.com
Tamrat
H
H
Bekana
M
M
D000034:Abortion, Veterinary / Q000453:epidemiology*; D000818:Animals; D001947:Breeding; D003338:Corpus Luteum / Q000502:physiology; D005002:Ethiopia; D005260:Female; D005865:Gestational Age; D008098:Litter Size; D006080:Ovarian Follicle / Q000502:physiology*; D010053:Ovary / Q000033:anatomy & histology / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D011247:Pregnancy; D011891:Rain; D012621:Seasons; D012756:Sheep / Q000502:physiology*