Abstract :
The lifetime performance of female sheep is one of the most important economic traits in
sheep husbandry. In this investigation, a Weibull model was used to study the effects of
‘breed’, ‘number of lambings’, ‘age at first lambing’, ‘type of birth’ and ‘farm’ on the length
of productive life (LPL). The data included records of 5191 female sheep of four different
breeds on 236 breeding farms in northern Germany. The observation period in which the
sheep were born or were removed from the farm ranged from January 2003 to December
2007. About 12% of the records were right-censored. All variables had a significant effect
on LPL at a level of p < 0.001 except ‘type of birth’. The German Blackheaded Mutton breed
showed the lowest risk ratio with 0.77 (SE = 0.17), while the Texel had the highest hazard
rate (1.00). The relative culling risk initially decreased from the first (5.73, SE = 0.09) to
the seventh lambing (0.36, SE = 0.12), and then increased until lambing number nine. The
highest relative culling risk was calculated at an age of 395 to less than 455 days at first
lambing (1.00). Animals younger than 395 days at first lambing showed the lowest risk ratio
(0.56, SE = 0.05). The culling risk for the effect ‘farm’ ranged from 0.3 to 3.1. A differentiation
of environmental, housing or management effects was not feasible with this data. But the
results offer some interesting options for further studies.
