Effect of weaning age on productive and reproductive performance of Lori-Bakhtiari ewes

The aim of this study was to investigate the effects of lamb weaning age on subsequent productive and reproductive performance of Lori-Bakhtiari ewes. 103 heads of lactating ewes with an average age of 3.5 years were allocated to one of three treatments as: 1.weaned early 2.weaned as in traditional sheep rearing or 3-weaned late. Rams were introduced at 60 days postpartum and were remained with ewes for 3 months. Ewes that became pregnant were remained in trial. Again, rams introduced to ewes at breeding season and were remained with ewes for 6 months. The proportion of ewes that exhibit estrus, interval from lambing to first estrus and to conception, lambing interval, conception rate and number of lambs' birth per ewes exposed to the rams were recorded. Gain rate of ewes was higher for treatments 1 and 2 in first month after weaning than other months (p<0.05). Percentage of estrus and conception rate after first parturition were significantly higher (p<0.05) for ewes in treatment 1 than treatments 2 and 3. After first parturition, ewes in group 1, returned to estrus and conception earlier compared to 2 and 3 groups (p<0.01). Average of 3 lambing interval was lower (p<0.01) for group 1 ewes than groups 2 and 3 . In second parturition, the number of lambs born per ewe exposed to the ram was higher (p<0.05) for group 1 ewes than 2 and 3 groups. It was concluded that ewe's performance were improved by weaning their lambs at 60 days of age.