Effects of the environment on dog semen parameters and testosterone concentration

Whether a mammal reproduces seasonally or continuously depends mostly on the environment and its effects on the endocrine pattern. Although the dog was the first species to have been domesticated, little information is available on the changes in reproduction that have occurred since. In this study, we evaluated whether environmental stimuli can act as modulators of male gonadal activity in the dog at the latitude of Bari (Italy). Therefore, for 1 year, serum and seminal testosterone (T) concentrations, together with seminal parameters, were recorded monthly and evaluated in relation to environmental variables such as temperature, humidity, and photoperiod. We found that, in temperate regions, the annual serum T profile is not affected by environmental conditions, whereas seminal T profile peaks in October and reaches its nadir in April. The percentage of progressive motile spermatozoa is also dependent on environmental cues. The results support the intuitive idea that recorded data require a proper analysis to be meaningful. In fact, we found that, in the dog, environmental changes appear to affect male gonadal physiology, and this is clear when recorded data are analyzed monthly; in contrast, pooling data into seasonal groups hides monthly environmental variations.