Seasonal variations in the cyclic luteal ovarian activity in the Tadmit ewe in Algeria

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Abstract
Seasonal variations of the cyclic luteal activity were assessed by measurements of progesterone concentrations in peripheral plasma collected daily or every 4 days, throughout 15 mo., in 16 Tadmit ewes, in Algeria. One female was cyclic at all times of the year; 15 ewes showed a period of cyclic luteal inactivity of < 53 days in 10 animals and ranging between 2.5 and 3.5 mo. for the 5 others (mean duration 52 days). The onset of ovarian inactivity took place from the beginning of Feb. to the end of April (mean date 19 March). The recovery of luteal function was much more definite; it occurred in May for 13 ewes (mean date for the 16 animals 10 May) when daylength was still increasing. These data suggest that at this latitude (36.degree.30''N) and for this particular breed of sheep (Tadmit) declining daylength is not the major environment stimulus for the resumption of breeding activity.

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