Seasonal variation in estrous activity in Ossimi and Rahmani ewes

E.F.uly, M.A.; Shafie, M.M.; Abdel Aziz, A.S.; Kandeal, S.A.

Egyptian Journal of Animal Production 17(1): 75-85


Accession: 000492836

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29 Ossimi [Ausimi] and 28 Rahmani ewes were studied for about 1 yr. Oestrous activity was measured as the percentage of females showing oestrus among those tested during a given month. Oestrous activity was significantly greater in summer (96.9% for both breeds combined) and autumn (94.4%) than in winter (78.2%) and spring (68.3%). It was not significantly affected by day length, by ambient temp. had a significant effect: a rise in temp. of 1 deg C was associated with an increase of 1.64 percentage points in oestrous activity. The interval from parturition to 1st oestrus was significantly longer in Ossimi (125.7 days) than in Rahmani ewes (62.6 days); this interval was not significantly affected by the age of the ewe. The av. duration of oestrus was significantly longer in Rahmani (31.5 h) than in Ossimi ewes (26.2), and (for both breeds combined) was significantly longer in summer (32.1 h) and autumn (31.3) than in winter (25.3) and spring (26.7). The duration of the oestrous cycle averaged 17.7 days, and was not significantly affected by breed or season. The number of oestrous cycles/ewe during the period of the study was 11.4 for all Ossimis and 13.1 for all Rahmanis; it was 17.2 for cycling ewes in both breed groups. The time spent not cycling amounted to 44.1% of the study period for the Ossimis that lambed and 37.3% for the Rahmanis that lambed. The difference was not significant.