Abstract
Ewe deaths affect the productivity and profitability in sheep farming systems and have potential animal welfare and market perception implications. Internationally, there is scant data on the timing and causes of ewe deaths in extensive grazing systems. There is no published literature on the incidence and risk factors associated with casting (ewe in late gestation accidentally immobilised, often in dorsal recumbency). This study, undertaken using a cohort of 1789 ewes on a New Zealand farm, reports on the timing and risk factors associated with production parameters for ewe deaths through an almost two-year period, along with causes of death during both peripartum periods. Ewe deaths occurred throughout both years but were most frequent during the peripartum (pre-lambing to mid-lactation) period. Casting was the most commonly identified cause of death in both years, responsible for approximately a quarter to a third of potential annual mortality. Few risk factors for death or casting were identified. In conclusion, the peripartum period is a high-risk time period for ewe deaths (and, by extension, will also contribute to lamb perinatal mortality). In extensively grazed flocks where casting events occur, it is recommended that all ewes are monitored daily during the peripartum period.
Highlights
Ewe deaths affect the productivity and profitability in sheep farming systems [1,2]and are an important issue in terms of potential animal welfare implications and market perceptions [3,4]
Ewe deaths occurred throughout both years of the study but occurred most frequently during the pre-lambing to mid-lactation period
20–24 day peripartum period each year were responsible for a quarter to a third of the potential annual ewe mortality on the farm
Summary
Ewe deaths affect the productivity and profitability in sheep farming systems [1,2]and are an important issue in terms of potential animal welfare implications and market (consumer) perceptions [3,4]. Reported ewe mortality rates in extensive outdoor grazing systems, such as in New Zealand, Australia and UK, are reported to be in the range of. Studies investigating ewe mortality rates and timing in extensive outdoor pastoral farming systems have largely focused on data collection at key production times (i.e., weaning, pre-mating, mid-pregnancy, and pre-lambing) with the estimation of mortality rates based on sheep missing at these times [8,12,13,14]. A large New Zealand study identified that the majority of ewes that went missing and were presumed to have died, or were reported as dead, did so over the mid-pregnancy to weaning period, but the causes of death were not investigated [8]. The timing of ewe mortality, as well as the causes and the relationship with productive parameters in outdoor grazing systems, require further investigation
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