The Effects of Extender Energetic Substrate Type on Goat Sperm Stored at 17 °C.

Artificial insemination in goats commonly relies on refrigerated semen doses, yet the optimal energetic substrate to support sperm metabolism remains unclear. This study aimed to evaluate the effects of different energetic substrates on goat buck sperm metabolism and motility when refrigerated at 17 °C. Semen from six Murciano-Granadina male goats were collected and diluted in PBS supplemented with 35 mM of either glucose, fructose, pyruvate, or lactate in the first experiment. In the second experiment, the effects of varying concentrations of pyruvate and/or glucose, NaCl supplementation, and the osmolarity on sperm quality parameters were assessed. Semen was stored at 17 °C for 48 h and evaluated for motility using the CASA system, as well as for viability, mitochondrial membrane potential, and mitochondrial ROS by flow cytometry. The results show that pyruvate and lactate extenders outperformed the others, preserving higher total motility, progressivity, and viability of spermatozoa over 48 h, even at a concentration lower than 35 mM, as in the case of pyruvate. In contrast, glucose had a detrimental effect on sperm quality, reducing viability and healthy population rates while increasing motility, especially at higher concentrations. NaCl supplementation and osmolarity had no significant effect on any of the sperm quality parameters. In conclusion, pyruvate maintains a higher quality and motility of sperm stored at 17 °C in PBS in comparison with a glucose-supplemented extender.