Zeranol is a semi-synthetic non-steroidal product used by chinchilla breeders to improve fur quality. The aim of this study was to assess the potential deleterious effects of zeranol in chinchilla at testicular level. For this purpose, 27 chinchillas received 6 mg of zeranol and 9 untreated chinchillas were used as control. Testicles were recovered after routine sacrifice, and the weight, length, width and testicular perimeter were recorded. Individual information regarding sex, age, weight at birth, at weaning and at sacrifice of chinchilla was obtained from the breeders records. The testes were processed for routine histological evaluation. Treated animals evidenced a significant reduction in testicular weight, length, width and perimeter. Histological findings included a reduction in the tubular lumen, loss of epithelium and disappearance of spermatozoids in the seminiferous tubules. Data suggests that zeranol produces toxic effects on the testis including degenerative damage in germ cells and Leydig cells, thus affecting spermatogenesis.

Key words: Chinchilla, Estrogen, Testicular degeneration, Zeranol