Impact de la mise en allaitement artificiel sur la santé, le comportement et les performances des agneaux

In sheep production, artificial rearing with commercial milk is frequently used to save lambs born fromlarge litters but is usually connected with poor animal performance. The objective of this study was to estimate the impact of this rearing method on the performance of lambs from the Romane breed, but also their short and medium-term immune and behavioual responses. Lambs were assigned to three rearing treatments: left with the mother (one lamb per dam), or separated at 3 days of age and fed either with a commercial milk substitute or with milk from Lacaune ewes milked daily. When weaned at 45 days, the lambs of the three treatments were mixed, reared in single sex groups and fed with hay and concentrate. Lambs fed commercial milk had significantly lower growth rate before 22 days than mothered lambs, those fed Lacaune milk being intermediate. No difference was detectable later on and the final weight was similar. Artificially reared lambs, regardless of the type of milk, seemed more active in their rearing pens and less afraid of humans in tests performed at 21 days. The fleece around the perianal area of lambs fed commercial milk tended to be dirtier than in lambs fed with ewe’s milk without any increase on the presence of pathogens in the faeces. Consumption of artificial milk was associated with lower antioxidant status and higher level of stress at 30 days of age compared to mothered lambs. The immune response following vaccination against chlamydiosis was not different between lambs fed artificial milk and those nursed by their mother. In this study where mortality rate was low, artificial rearing was seen to impair growth rate and antioxidant status and to promote a lamb human relationship only during the artificial rearing period