Age-related variations in the testes and prostate of beagle dogs

Variations in the weight and histology of the testes and prostate of Beagle dogs are described. Data were abstracted from records of toxicity studies performed at the Huntingdon Research Centre during the years 1967--77. A sample of 198 dogs aged between 37 weeks and 7.75 years was analysed. When juvenile dogs are studied, a significant proportion show low testicular weight, incomplete spermatogenesis and immature prostate development after 13-week observation periods. The occurrence of these normal variations may complicate the assessment of gonadal toxicity. In other respects, relatively few spontaneous variations from normal are likely to be encountered in these organs after observation periods lasting up to 2 years. 10% of dogs maintained for a 7-year observation period developed testicular neoplasms and a further 8% showed interstitial cell hyperplasia. Epithelial hyperplasia of the ductus epididymis and benign prostate enlargement were also normal features of the aged male Beagle.