Loading-related injuries of mechanically loaded broilers under field conditions

This publication is part of a large study whose objective was to assess animal welfare during 32 mechanical loadings of broilers. We here focus on animal health aspects and the influences of circumstances during mechanical loading. Broilers in two husbandry systems (HS) (mean number of fattening days: HS 2: 41.3 days; HS 3: 40.1 days) were assessed on-farm for loading-related injuries such as fractures, hematomas, and abrasions before and after mechanical loading. The influence of conveyor belt speed (fast vs. slow), container type (GP container vs. SmartStack container), HS, fattening method (FM), season, and sex on loading-related injuries was analyzed. The two HS were grouped according to the specifications of a retail trade label into three FM (HS 2: Standard and Standard Premium, HS 3: Premium), which differed, among other aspects, in genotype, stocking density, dark period, and access to a veranda. Hematomas on the wing (6.55%) were the most common type of injury followed by hematomas on the wing tip (6.17%), abrasions on the body (4.92%), abrasions on the wing tip (4.25%), severe wing injuries (1.13%), and hematomas on the wing proximal to the wing tip (0.38%). A reduction in injuries was achieved by a slow belt speed, the use of a SmartStack container, and loadings during spring and summer. Loading broilers of HS 3 compared with those of HS 2 led to a significantly lower risk of severe wing injuries, total abrasions, and wing tip abrasions. Broilers of the Standard Premium (P = 0.038) and Premium FM (P = <0.001) had a significantly lower risk of severe wing injuries than those of the Standard FM, demonstrating that not only the genotype, which is one of the major differences between HS 2 and 3, influences the injury rate. Other differences in FM, such as a longer dark period, a lower stocking density at housing, more enrichment, and access to a veranda should be considered as influencing factors.