Effects of Incubation Temperature at 37 °C on Canine Sperm Quality Before Cooling to 5 °C

Background: One of the most important aspects of artificial insemination in animals is the practical design of long-term preservation of sperm. Although there are many reports on canine sperm storage methods, an improved system for chilling canine spermatozoa is required for successful breeding programs in companion and working dog colonies. Objectives: This study aimed to compare the effects of incubation temperature at 37 °C on dog sperm parameters before cooling. Methods: Around 1-2 mL ejaculated sperm from the testes of 5 mature, healthy dogs were collected and divided into two groups: C: TRIS+egg yolk 20% (control, without incubation at 37 °C), T: TRIS+egg yolk 20% (treatment group, incubation at 37 °C for 10 minutes). Evaluation of cooled sperm was done by computer-assisted sperm analysis (CASA) for motility test, morphology, eosin-nigrosin vital staining and hypo-osmotic swelling test (HOST) after cooling. Results: In the treatment group, total and progressive motility (PM), curvilinear velocity, straight line velocity, average path velocity (VAP), linearity (LIN), straightness (STR), the proportion of sperm with normal morphology, the proportion of viable sperm and the proportion of sperm positive for HOST were not affected by the interaction of group by time. However, they were lower in treatment than the control group (P<0.05) and they decreased throughout preservation (P<0.001). Conclusion: Keeping sperm at a temperature of 37 °C and applying heat shock by bain-marie has highly adverse effects on the quality of ejaculated sperm.