The effect of energy intake level (EIL) and body condition score (BCS) on ovulation rate (OR) in Iranian fat-tailed ewes, and role of leptin in this phenomenon has not been cleared. Therefore, two experiments carried out in fat-tailed Shal ewes. experiment was conducted to study the effect of EIL on body weight (BW), BCS, OR and their relationships in a long period. 2” experiment designed to study the effect of EIL and leptin administration on OR in a short period. In the 1” experiment, synchronized ewes were fed a ration which provided 60% (0.6M; n=14) or 100% (M; n=14) maintenance energy requirements for 5 oestrous cycles. In the 2nd experiment, 24 synchronized ewes were assigned randomly in to three groups and received the following treatments for 4 days. Group I (n8) were fed a ration which provided 100% maintenance energy requirements and infused with l mg/kg recombinant human leptin. Group II (n8) and III (n=8) were fed a ration which provided 180% and 100% maintenance energy requirements respectively, and infused with 1ml normalsaline saline. BW, BCS and OR were determined in each oestrous cycle. In the I”’ experiment, BW and BCS significantly (P<0.0l) decreascd in 0.6M group and indicated a positive correlation (R2 = 0.62). OR in 0.6M group,
significantly (P<0.01) decreased when BCS<2. Ovulation was stopped when BCSI. In the 2” experiment, there were not any significant differences in BW, BSC and OR between experimental groups. Results suggest that OR in fat-tailed ewes responded to changes of EIL, BW and BCS later than thin-tailed ewes.
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