Scrotal width as an index of testicular size in dogs and its relationship to body size

Measurements of scrotal width were strongly correlated with testicular weight in 71 dogs (r = 0–919) and thus provided a convenient index of testicular size and potential sperm production. However, to be useful in trying to predict male fertility this measurement had to be adjusted for bodyweight. A graph is presented which allows estimation of ‘average’ scrotal width and its 95 per cent confidence limits for potentially fertile dogs of bodyweight between 5 and 50 kg. With one exception, dogs with scrotal widths below the 95 per cent confidence limits had very few or no spermatozoa in smears from the cauda epididymidis.