Influence of photoperiodic treatment of rams on the ovulatory response of Ile-de-France ewes to the male effect during seasonal anestrus.

This dataset compiles experimental data on the sexual activity of Ile-de-France rams, either subjected or not to a light treatment, and their ability to stimulate the resumption of ovulatory cycles in anovulatory ewes during seasonal anestrus under natural photoperiod conditions. Twelve two-year-old rams were randomly allocated to two groups of six and housed under natural photoperiod before being transferred on November 4, 1998, to a light-tight facility. The control group was exposed to a simulated natural photoperiod from November 9, 1998, to February 28, 1999, whereas the light-treated group received a long photoperiod (16 h light/day) for 66 days followed by a short photoperiod (8 h light/day) for 46 days. The sexual activity of rams was monitored by measuring testicular volume every two weeks and by determining plasma testosterone concentrations from weekly blood samples collected at 9:00 a.m. The male effect began on March 1, 1999, the day after the light treatment ended. Primiparous and multiparous Ile-de-France ewes (n=120) were kept under natural photoperiod, isolated from males, and then randomly assigned to three age-balanced groups (40 ewes each). Group A was not exposed to rams throughout the experiment, whereas the other two groups were exposed to rams for 14 days, with six rams introduced per group starting on March 1, 1999 (day D0). Group B was exposed to the control rams. Group C was exposed to the light-treated rams. Plasma progesterone was measured before the male effect (days D-14 and D-6: February 15 and 23, 1999) to determine the proportion of cycling ewes, then three times per week (Monday, Wednesday, Friday) from day D0 to day D28 (March 29), to characterize corpus luteum activity as an indicator of the ovulatory response to the male effect.