Spermatogenesis and testicular tumours in ageing dogs

The aims of this investigation were to quantify the changes in canine spermatogenesis that occur during ageing and to study the prevalence of testicular tumours and their effects on spermatogenesis in dogs. Testes from 74 dogs of various breeds without clinically detected testicular disease and from 28 dogs with clinically palpable tumours were examined. Testicular tumours were classified histologically according to the criteria of Nielsen and Kennedy (1990). Spermatogenesis was evaluated using a modified Johnsen score adapted for use in dogs. The diameter of the seminiferous tubules was measured in dogs without testicular disease to examine the possible effects of ageing. The different lifespans of small and large breeds were compensated for by expression as a percentage of the age at which dogs with various body weights are considered to be geriatric. Of the dogs without clinically detected disease, 21 of 74 had small testicular tumours. As in the 28 dogs with clinically detected tumours, multiple types of tumour and bilateral occurrence of tumours were common findings. The prevalence of tumours increased during ageing. Eighty-six per cent of the clinically detected tumours and 57% of the non-clinically detected tumours were found in geriatric dogs. The diameter of the seminiferous tubules did not change with age. Impairment of spermatogenesis was found only in dogs with bilateral tumours and in the affected testis of dogs with clinically detected tumours. In conclusion, it appears that spermatogenesis per se does not decrease during ageing in dogs. However, the occurrence of testicular tumours increases with age and this may affect spermatogenesis significantly.