Lung lesions at slaughter: associations to factors in the pig herd.

A survey was made of available data files to gain a preliminary insight into the association between environmental factors and the prevalence at slaughter of lung lesions. Herd size was the factor that showed the most predominant association with the prevalence of lung lesions. This was largely independent of the recruitment system for weanlings. There was a moderate trend toward positive association between the prevalence of lung lesions and the prevalence of other lesions. Lung lesions were weakly but significantly associated with the occurrence of infectious diarrhoea in the herd. The investigation demonstrated the feasibility of and the need for continuous epidemiological studies to identify disease determinants. Studies of the nature reported here makes it possible to define essential health factors with an accuracy that could never be achieved through clinical observations in a few herds.