The aim of this study is to investigate the possibility of a compensatory growth after starving and re-feeding of ewe lambs, the effects on puberty onset and the related endocrinology events.

Three groups of 12 Sardi ewe lambs are fed according different schemes: HH: high level diet, LL: low level diet and LH: low level diet for 2 months and high level for 4 months. The low level diet consists in straw (500 g) and concentrate (200 g) while in high level diet the concentrate is given ad libitum. The assay begins at July 1 when the lambs are 7 months old and stops at December 30; blood samples are taken thrice a week for P4, FSH, GH and Leptin assays.

There is no compensatory growth in fasted-refed lambs, the average daily gain (ADG) during the second period of diet being 80±8 g for HH and 77±20 g for LH. The onset of puberty is mainly related to the live-weight, all the ewes reaching the puberty had between 28 and 35 kg LW at this time, lightly heavier in HH group (32,8±2,8 vs 30,5±1,3 for LH and 30,0 for the only ewe reaching puberty in LL group; P<.05). At individual level or at group level, no significant relationship can be measured between the time of puberty and the plasma levels or GH, Leptin nor FSH. There is no correlation between plasma Leptin and live weight or ADG during the 15 days period before the blood sample except during the end of the assay between LW and leptin. The GH and FSH levels in LL group are higher (P<.05) than in LL and LH group.

There is a significant difference between the growth rate during low or high diet periods but the average daily gain in the best conditions is generally <100 g/d. The growing lambs are in good body conditions but never fatty; it would be the reason for the lack of a constant correlation between LW or ADG and plasma Leptin levels.