In order to investigate the endocrine events leading to puberty in ewe lambs fed at different levels, 3 groups of 10 Sardi ewe lambs are followed: HH fed with a high level diet, LL with a low level diet and LH with low level diet for 2 months and high level for 4 months; the L diet consists in straw (500g) and concentrate (200g) while in H diet the concentrate is given ad libitum; the assay begins at July 1 when the lambs are 7 months old (average LW: 22 kg) and stops at December 30. Blood samples are taken thrice a week for P4, FSH, GH and Leptin assays and complete puberty is assessed by P4 > 1ng/ml for >=3 successive values and oestrous behaviour

Onset of puberty : all lambs reached puberty in the well-fed group, but only 8/10 and 1/10 in LH and LL groups respectively. The live-weight at puberty is quiet the same for the 3 groups, 32, 31 and 30 kg for HH, LH and LL groups.

The FSH secretion pattern is classical : an increase for about 1 month before the first ovulation and a decrease in the average levels after the onset of puberty

There is a significant negative relation between FSH and Leptin, and no correlation between FSH and GH

The results confirm the importance of body development on the appearance of puberty, and raise the possibility of a compensatory growth in Sardi ewe lamb. The FSH concentrations were not significantly altered by feed restriction. The negative relationship with plasma Leptin levels may reflect the strengthening of a negative feedback on FSH secretion after puberty.