Formaldehyde-contaminated feed induces histopathological changes in the testes of adult pigeons (Columba livia)

Formaldehyde (FA), a ubiquitous environmental pollutant, has long been suspected to possess reproductive toxicity. Here, we investigated the histopathological alteration of male gonads following exposure to FA-contaminated feed (40% aqueous solution of FA; 2.5 ml formalin/kg feed) in pigeons for 7 days. The mean body weights were not changed significantly in FA-contaminated feed exposed pigeons compared with control pigeons. The hemoglobin concentration was significantly decreased and serum enzyme aspartate transaminase (AST) was significantly increased in FA-exposed pigeons in comparison with control pigeons. Histologically, the structural components of the testes are the seminiferous tubules and interstitial tissues, which are surrounded by a connective tissue capsule. In control pigeons, the size and shape of seminiferous tubules were normal with a regular arrangement of spermatogenic cells. In FA-exposed pigeons, the testicular capsule was thickened and degeneration of spermatogenic cells in the seminiferous tubules was observed. The number of spermatogenic cells was significantly decreased in the seminiferous tubules of FA-exposed pigeons in comparison with control pigeons, indicating that the low exposure of FA affects the spermatogenic cells' populations in male birds. The present results suggested that FA might cause infertility in birds.