Implications for welfare, productivity and sustainability of the variation in reported levels of mortality for laying hen flocks kept in different housing systems: A meta-analysis of ten studies

摘要

Data from ten sources comprising 3,851 flocks were modelled to identify variation in levelsof mortality in laying hens. The predicted increase with age was curvilinear with significantvariation between the seven breed categories. Mortality was higher in loose housing systemsthan in cages and variable within system, confirming previous reports. Cumulativemortality (CM) was higher in flocks with intact beaks (χ2 = 6.03; df 1; p = 0.014) than inthose with trimmed beaks. Most data were available for free-range systems (2,823 flocks),where producer recorded CM at 60–80 weeks of age averaged 10% but with a range from0% to 69.3%. Life cycle assessment showed that the main effect of increased levels of henmortality is to increase the relative contribution of breeding overheads, so increasing environmentalburdens per unit of production. Reducing CM to levels currently achieved by the1st quartile could reduce flock greenhouse gas emissions by as much as 25%. Concurrentlythis would enhance hen welfare and better meet the expectation of egg consumers. Moreresearch to understand the genetic x environment interaction and detailed records of thecauses of mortality is required so that improved genotypes can be developed for differentsystems and different breeds can be better managed within systems.