ABSTRACT
The pathomorphological study was carried out on a total of 360 broiler chicken which had been random-sampled on days 22 and 35 of the mast period, respectively, from those flocks that were to be compared. Furthermore, 161 animals with evidence of movement disturbance that were slaughtered in the last two mast weeks, were also evaluated. With regard to incidence, severity of movement disturbance and the spectrum of pathomorphological changes of the skeleton there were no differences between the different groups. When histological and morphometrical methods were applied, no differences in the skeleton structure were noted between flocks with conventional housing and flocks with reduced population density. Equally, no differences were ascertained with regard to dry substance and ash content of the bones including the minerals calcium and phosphorus. Furthermore, there were no group differences in serum calcium, phosphorus and alkaline phosphatase. In numerous chicken from all groups a plantar pododermatitis with differing incidence and strongly varying intensity was observed. The lesions were characterized by a papillomatous proliferation of the basal epithelial layers. There was widespread inflammation with loss of the epithelial layer and deep necroses of the sole. A latent infection with papilloma viruses is discussed. About 90% of the random-sampled chicken of all groups showed bending of the vertebral column by 20 degrees at the height of the 6th thoracic vertebra. In numerous chicken the 6th thoracic vertebra was dislocated and slightly rotated which caused encroachment of the vertebral canal. Whether this alteration may be responsible for the frequently observed movement disturbance of broilers in the last third of the mast period can not be decided on the basis of the pathomorphological study. In any case it must be assumed that both the pododermatitis and the bending and encroachment of the vertebral column cause pain. Thus, both lesions should be evaluated from the viewpoint of animal protection.
