Broiler mortality during transport to abattoirs (dead-on-arrival/DOA) evokes concern due to compromised animal welfare and associated economic losses. The general aim of this study was to characterize pathological lesions associated with mortality in broilers close to slaughter. The specific aim was to investigate whether disease at the end of the growth period may be a predisposing factor for DOA by describing and comparing the pathological findings in broilers dead-on-farm (DOF) in the final days of the production cycle and in broilers DOA from the same flocks. Gross post-mortem examinations were performed on 607 broilers from 32 flocks, either DOF (371) or DOA (236). In DOF broilers, the most common pathological lesions were lung congestion (37.7%), endocarditis (29.4%), and ascites (24.0%), whereas the most common findings in broilers DOA were lung congestion (57.2%) and trauma (24.6%). Lung congestion was more prevalent among DOA broilers compared to DOF broilers (P-value of > 0.001). A possible cause behind the pathological finding lung congestion is sudden death syndrome (SDS). The study indicates that steps in the transportation process per se cause the majority of pathological lesions such as lung congestion and trauma that may have led to the mortalities registered. Pre-existing diseases such as ascites and osteomyelitis may also predispose for DOA. Thus, factors relating to on-farm health, catching, and transportation are all areas of future investigation in order to reduce transport mortalities and to enhance welfare in broilers.
A prospective longitudinal field study was conducted in the period from January 1994 to January 1996 to analyse the relationship between some selected risk factors in the growing and laying periods and (1) the flock-level occurrence of Marek's disease (MD) during the period from 16 to 32 weeks of age and (2) the cumulative mortality during the same period. A total of 171 layer flocks in 102 egg-production farms were included in the statistical analyses.A logistic regression (with strain of layer and vaccination program against MD as fixed effects) of flock-level MD-status during the first 16weeks of the laying period was conducted. Of the risk factors investigated, "multi-age management" and "housing system" were significantly associated at the rearing farm, and "number of hens in each cage" at the egg-production farm. Flocks kept in single-age facilities had a lower risk of MD than flocks housed in farms with multi-age management. The odds of MD were larger for flocks housed on a litter floor in the rearing farms compared to flocks housed in battery cages. At the egg-production stage, flocks kept in battery cages housing more than three hens were at greater risk of MD than those held in cages for three hens or less.A weighted least-squares regression (with strain of layer and flock-level MD-status as fixed effects) of cumulative mortality during the period from 16 to 32weeks of age was also run. The same risk factors (with the same directions of effects) and "size of the rearing farm" were included in the final model of mortality. Chicks reared in medium-sized farms were at higher risk of dying than those coming from either small or large rearing farms. Our results confirm the importance of preventing chicks from being exposed to MD-virus during the rearing period, to reduce the risk of MD-outbreaks (and thereby, mortality losses) during the early stage of the egg-laying period.