| Summary: | Ewe Lambs Early Breeding of the Endogenous Breeds of Sheep in Tunisia. Over 5 successive years, 9 to 10-month-old female sheep of the Barbarine (n = 746) and Queue Fine de l'Ouest (n = 166) breeds were early mated under semi-arid field conditions. The overall conception rate was about 63 % showing major differences between years (P <0.001). Higher growth rate between 10 and 30 days of age and live weight at early breeding definitely increased conception rates ; the breed, growth rate between 30 and 70 days of age and weaning live-weight had no effect. The records for the 5 years on both breeds showed a highly significant (P <0.001) relationship between the proportion of female lambs mated when early exposed to the rams and the proportion of those lambing. In other experiments, the effects of level of feeding, of a progestagen/PMSG treatment or of their combination on the success of early breeding ewe lambs were investigated. Treating the female lambs with progestagens/PMSG or improving their feeding level prior to early mating lead to a increase (P <0.05) of at least 20 points in conception rate. There was no advantage of combining both treatments. Treatment with progestagens/PMSG can advance lambing date by approximately 2 weeks (P <0.05) without any effect on litter size.
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