Long days in winter or the presence of adult sexually active rams did not influence the timing of puberty of autumn-born Rasa Aragonesa ram-lambs

Abstract

ABSTRACT Forty autumn-born ram-lambs were used to study the effect of several rearing strategies on their sexual activity and fertility at 8 months of age. The animals were assigned to one of the following four groups (n = 10): FA, which were exposed to 2 months of long days (15 January–15 March); SAR, which were housed with three Sexually Activated adult Rams from 15 March to 20 June; NAR, housed with three Nonactivated adult Rams, and Control (C), kept isolated from adult rams throughout the experiment. In mid-June, individual and group ram serving-capacity tests were performed. Mean plasma testosterone levels (ng/ml) throughout the experiment were higher (P < 0.001) in the C (4.4 ± 0.2) and SAR (4.3 ± 0.2) groups than in the FA (3.4 ± 0.2) and NSA (3.4 ± 0.2) groups. In the serving tests, control ram-lambs executed a higher total mean number of sexual events than the other groups (P < 0.05). Fertility rates of SAR- (90%) or C-mated ewes (100%) were higher (P < 0.01) than ewes mated by the FA (50%) and NAR (40%) ram-lambs. In conclusion, autumn-born ram-lambs reared in isolation from adult congeners had the highest sexual activity and fertility at 8 months of age, which suggests that no special rearing strategy is necessary to induce puberty in these rams.