Testicular measurements and daily sperm output of Tori and Estonian breed stallions

Evaluation of testicular measurements and daily sperm output (DSO) yields valuable information for predicting the reproductive capacity of stallions. The present study evaluated testicular measurements (height, length, width and circumference) and DSO of eight Tori and eight Estonian breed stallions. One ejaculate of semen was collected daily for 10 subsequent days from each stallion. The gel-free volume of semen was measured with a graduated glass cylinder and the sperm concentration was assessed with a Chorjajev chamber. The volume of gel-free fraction was multiplied by the sperm concentration to give the total number of spermatozoa (TSN). The DSO was calculated as mean TSN of collection on days 8-10 in Tori breed stallions and on days 4-10 in Estonian breed stallions. The DSO of Tori breed stallions was 12.9 x 10(9) spermatozoa and of Estonian breed stallions 4.5 x 10(9) spermatozoa (p < 0.001). Testicular measurements (in cm) 1 day after the last semen collection were as follows: left testis - height 7.3, length 10.4 and width 7.3 in Tori breed stallions, and 5.9, 8.1 and 5.9, respectively, in Estonian breed stallions; right testis - height 7.4, length 10.6 and width 7.4 in Tori breed stallions, and 5.5, 7.4 and 5.3, respectively, in Estonian breed stallions. All these testicular measurements were significantly smaller in Estonian than in Tori breed stallions (p < 0.001). Testicular circumference was 45.4 and 35.4 cm in Tori and Estonian breed stallions, respectively (p < 0.001). The testicular circumference was correlated with DSO in both Estonian (p < 0.05) and Tori breed stallions (p = 0.071). The results give us valuable information on the reproductive capacity of Tori and Estonian breed stallions.