LAUSR

Abstract To evaluate the effects of nutrition on the sexual behaviour of ewes, forty-eight mature (7.6±1.9years old) Merino d'Arles ewes with an average initial body condition score (BCS=2.26±0.23) and similar body weight (BW=46.6±3.8kg) were fed three contrasting diets for three months. The diets provided varying levels of energy expressed as proportion of Maintenance Energy Requirements (i.e. Low=70%MER; Medium=113%MER and High=180%MER) with the ultimate objective of obtaining different BW and BCS. Blood samples were taken before and at the end of the three-month experimental period to measure plasma metabolites (glucose, GLU; beta-Hydroxybutyrate, βOHB; non-esterified fatty acids, NEFA) and hormones (insulin, INS and leptin, LEPT). The ewes' sexual behaviour, e.g. attractiveness, receptivity and proceptivity, was estimated through normalized pen-tests before and at the end of the experiment after hormonally-induced oestrus. As expected, the dietary treatments induced significant changes in BW (i.e. the final weights were 38.6±2.5, 47.3±3.6 and 55.0±2.2kg for Low, Medium and High groups, respectively) and BCS (1.33±0.4, 1.90±0.2 and 2.33±0.2 for Low, Medium and High, respectively). The metabolic and hormonal changes were in agreement with the known effects of feeding regimes. The sexual behaviours of ewes were only partially changed by feeding regimes. While the scores of receptivity (SR) of ewes to males (i.e. number of agonistic interactions with the courting ram) and scores of proceptivity (SP) towards rams (i.e. time spent close to a pen with rams) remained unchanged (P>0.05), there were significant (P 2 =0.79; P