Testicular atrophy in Columbian black-tailed deer in California.

During an 18-year period, 4.1% (34/831) of male deer (Odocoileus hemionus columbianus) killed on a field station during the autumn hunting season had velvet-covered, often misshapen antlers, and at least two deer had testicular atrophy (gonads from most deer were not available for examination). Testes from six similarly affected deer and several normal deer were compared histologically. Lesions ranged from hypocellularity of the semeniferous tubules and relative hyperplasia or degeneration of interstitial cells to complete connective tissue replacement of the testicular parencyma. Chronic vascular changes were present in several testes. The etiology and pathogenesis of the lesions were not determined.