Feeding pre‑pubertal Tibetan sheep extra nutrients during the cold season (either concentrate feed or mineral lick blocks) helped them grow faster, increased the number of ovarian follicles, and raised key reproductive hormones. The study also showed that better nutrition turned up the activity of the kisspeptin (KiSS‑1) system in the brain, which in turn boosted the whole reproductive hormone cascade.

We examined the development of the reproductive system in prepubertal Tibetan sheep ewes when fed only oat hay (CON) or supplemented with either lick blocks (BS) or concentrate feed (CS) during the cold season. The average daily gain of the CS ewes was greater than that of the BS ewes (P < 0.05), which was greater than that of the CON ewes. The same pattern was observed in the number of ovarian follicles (P < 0.001), that is, CS > BS > CON. Serum concentrations of gonadotropin-releasing hormone, follicle-stimulating hormone, luteotrophic hormone, estradiol and progesterone in the CS and BS groups were higher than in the CON group (P < 0.05). The messenger RNA (mRNA) expression of KiSS-1, GPR54 (G protein-coupled receptor 54), ERα (estradiol receptor α) in the hypothalamic anteroventral periventricular area of the CS group were higher than in both the BS and CON groups (P < 0.05), while the BS group was higher than in the CON group (P < 0.05). Similar differences among groups were observed for gonadotropin-releasing hormone receptor mRNA expression in the pituitary, follicle-stimulating hormone receptor and luteinizing hormone receptor mRNA expression in the ovary. These results indicated that the KiSS1/GPR54 system was more active with nutrition or trace mineral supplementation during the cold season. The system stimulated the hypothalamic-pituitary-gonadal axis and enhanced folliclar development in prepubertal Tibetan sheep ewes. We concluded that energy, protein and trace minerals supplements could improve the reproductive performance of Tibetan sheep on the Qinghai-Tibetan plateau.