[Annual variations in plasma prolactin and testosterone concentrations in the Ouled-Djellal ram in Algeria]

Plasma concentrations of prolactin and testosterone were measured weekly, from November 1976 to December 1977, respectively in 29 and 10 Ouled-Djellal rams penned in the Algeria area. Plasma prolactin and testosterone levels exhibited concomitant seasonal variations: they were low in November-December, then they increased from January to maximal values in summer through two steps, the first in February-March, the second in June-July. Taken all around, the hormones changes paralleled those of photoperiod. The synchronism in annual variations of prolactin and testosterone secretory patterns is a feature of the Ouled-Djellal ram. Results are discussed in relation to effects of prolactin on testicular activity.