Risk factors for Dead on Arrivals during broiler chicken transports

The pre-slaughter phase is a critical phase of the production process, with severe implications for broiler welfare and profitability, such as death (Dead on Arrival %; DOA%). In order to effectively reduce DOA%, a better understanding of its risk factors is needed. Specifically thermal stress has been identified as an important underlying factor for DOA%. Thus, the aims of this study were to investigate the link between DOA% and pre-slaughter characteristics, and between DOA% and behavioural indicators of thermal stress. Transports (n=79) from 52 broiler farms to 5 slaughter plants in Belgium were assessed. Data were collected on DOA% (recorded by slaughter plant personnel), flock information (provided by the farmer), potential pre-slaughter risk factors (including weather conditions and pre-slaughter phase duration), body temperature, in-crate panting, and huddling prevalence (44 crates/transport). A multivariable linear regression model was built with an automatic stepwise selecti on procedure. Association between DOA% and behavioural data were tested with Spearman’s rank correlation coefficients. Mean (±SD) size of transported flocks was 48,453±27,168 birds, with a mean age of 41.2±1.3d and weight of 2.58±0.4kg. Mean pre-slaughter phase duration was 440±143min. Median DOA% was 0.19% (range 0.04-3.34%). The model (R2=29%) showed that more DOAs were found when farmers did not check chick quality upon arrival (0.51% vs. 0.21% when checked; P=0.012), when birds were caught by acquaintances (0.46% vs. 0.27% when professionally caught; P=0.01), when birds were heavier at slaughter (P=0.046), and when they were kept outside during lairage (0.38% vs. 0.27% when laired inside; P=0.045). DOA% was positively correlated with body temperature (ρ=0.29; P=0.012), but did not correlate significantly with panting or huddling prevalence (both P>0.5). These findings suggest that broiler welfare may be improved by adjusting the farmers’ management, inclu ding checking chicks upon arrival. Slaughtering broilers earlier in life (or at lower body weights), using a professional team for catching, and keeping the birds inside a warehouse during lairage, appear to be promising strategies for reducing DOAs as well. Additionally, a link between thermal stress (as indicated by body temperature) and DOA% was found, although this was not reflected in the behavioural indicators. In order to effectively reduce DOA% further research is needed to investigate whether the relations with the identified risk factors are causal.