Effect of the Feed Level on the Seasonality of the Sexual Activity of Timahdite Ewes: Role of the Leptin and IGF System

The effects of the feed level on the seasonality of the sexual activity were studied in Timahdite ewes in the Middle Atlas region of Morocco (33°N). Non pregnant and non lactating adult ewes (3-4 years) were allocated to two groups according to two diet levels: HL (n = 10) received double the maintenance requirements and LL (n = 9) the maintenance requirements. Over a one-year period, estrus was recorded twice daily and blood samples were collected weekly to determine progesterone, leptin, IGF-1, IGFBP-2 and IGFBP-3 plasmatic levels. The higher feed level stimulated the reproductive activity in HL ewes, which presented a longer reproductive season and a significantly higher number of normal estrous cycles than LL ewes (7.8 ± 1.4 vs 3.9 ± 1.9, respectively; P < 0.05). Leptin, IGF-1 and IGFBP-2 seemed involved in the stimulation of the reproductive activity. Compared with LL ewes, HL ewes showed significantly higher plasmatic levels in leptin (3.79 ± 0.38 vs 3.30 ± 0.29 ng/mL; P < 0.05) and in IGF-1 (76 ± 28 vs 58 ± 21 ng/mL; P < 0.01), and a significantly lower level in IGFBP-2 (68 ± 21% vs 99 ± 24%; P < 0.01). No significant difference was recorded between the two groups regarding the IGFBP-3 levels (103 ± 52% vs 96 ± 17%; P > 0.05). These results showed that the Timahdite ewe exhibited a seasonal reproductive pattern which was modulated by the feed level.