Semen parameters and testicular dimensions in small breed dogs below ten-kilogram bodyweight

Because of few available data on semen parameters in small breed dogs, the study aimed to analyse semen and measure testes of dogs ≤10.0 kg bodyweight. Semen was collected from 41 fertile stud dogs, which were divided based on bodyweight: group 1 ≤ 5.0 kg and group 2 between 5.1 and 10.0 kg. Median values for ejaculate volume (group 1: $$ 1.2 ml; group 2: $$ 2.2 ml), total sperm output (group 1: $$ 110.7 × 10⁶ ; group 2: $$ 215.1 × 10⁶ ) and testicular volume (group 1: left testicle $$ 2.8 ml, right testicle $$ 2.7 ml; group 2: left testicle $$ 5.5 ml, right testicle $$ 5.0 ml) were lower in group 1 compared to dogs of group 2 (p = .001; p = .001; both testes: p < .001). There was no difference in sperm concentration (p = .985). Based on these results, introduction of an additional weight group to the commonly used reference values is recommended, since values for ejaculate volume, total sperm output and testicular dimensions for dogs ≤5.0 kg bodyweight differed significantly from values of dogs with a bodyweight from 5.1 to 10.0 kg.