Outdoor lambing without shepherd help : neonatal lamb mortality

Abstract

The mortality rate at 48 hours of age of Lacaune lambs born in the open in extensive conditions reaches 24 % : 33.5 % of this mortality are related to physical or biological problems in mothers and their offspring, 38.5 % are related to the mother’s comportment, 12 % to weather conditions and 16 % allocated to unknown causes. As more than a third of this mortality rate is related to the behaviour of mothers, the effect of their prelambing behaviour on lamb mortality was studied. Thus, non-isolation induced 7 % of lamb mortality related to disturbance by the flock. This mortality concerned mostly lambs from primiparous females which isolated themselves half as frequently as multiparous females. On the contrary, isolation behaviour induced 5 % of lamb mortality due to disappearance or fox predation. This mortality concerned mostly the lambs of multiparous females and twins. Lastly, the desertion of new borns was the cause of 26.5 % of lamb mortality. This mortality concerned mostly the lambs of primiparous females which deserted their lambs 8 times more frequently than multiparous ewes. Concerning the shelter seeking behaviour, we recorded an average of 12 % of lamb mortality related to meteorological condition. Though more than half of ewes lamb sheltered from the wind in shruby areas when the wind speed was ≥ 3m/s, this behaviour did not protect the new-borns from heavy rain. Thus mortality rate related to meteorological conditions fluctuated between 0 % in mild weather conditions and 27 % in bad years.