The histology and ultrastructure of ectopic cartilaginous and osseous nodules in the lungs of young broilers with an ascitic syndrome

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Abstract
The histology and ultrastructure of ectopic cartilaginous and osseous nodules present in lungs of young broilers with an ascitic syndrome and reared at two locations were examined. There were significant increases in the numbers of nodules observed in the lungs of birds with an ascitic syndrome compared with control birds. Institute‐reared birds had more lung nodules per section than those commercially‐reared, possibly resulting from inadequate ventilation. Histologically, these nodules contained more chondroitin sulphate proteoglycans than keratan sulphate. Haemosiderin was also demonstrated within the nodules, possibly indicating previous pulmonary haemorrhage. The nodules matured from hyaline, fibrous and mineralised cartilaginous to osseous forms, with the fibrous variety being the most frequent in both rearing programmes. In lungs of ascitic birds when there was a high incidence of nodules, large areas of the parenchyma contained bundles of non‐mineralised collagen fibres. It was suggested that birds with an ascitic syndrome maintained in a possibly hypoxic environment develop pulmonary fibrosis which could lead to an increase in the number of nodules found in the lungs.