Evaluation of temperature-dependent "thermotaxis (termotaksi)" behavior in goat sperm

Thermotaxis is defined as the directional movement of spermatozoa in response to temperature gradients, and it has been reported to play a significant role in the fertilization process. While the presence of thermotaxis has been well-documented in several mammalian species such as humans, rabbits, and mice, there is a lack of scientific information on this phenomenon in small ruminants, particularly in goat spermatozoa. This study aimed to investigate the thermotactic orientation of goat spermatozoa obtained from fresh ejaculates under controlled laboratory conditions using vertical thermal gradients (33°C, 38°C, and 41°C), and to evaluate the effects of different temperatures on sperm morphology, membrane integrity, viability, and kinetic parameters. Ejaculates collected from Alpine bucks were incubated at the specified temperatures for 45 minutes, and sperm samples from each thermal fraction were assessed in detail for concentration, membrane integrity (HOST test), viability (Nigrosin-Eosin staining), and kinetic parameters using the CASA system. The results demonstrated that spermatozoa predominantly migrated toward the 33°C compartment, where they exhibited higher motility (78.4%), progressive motility (73.1%), better membrane integrity (61.7%), and viability (67.1%). In contrast, the spermatozoa in the 41°C compartment showed significantly reduced motility (66.6%), progressive motility (60.9%), membrane integrity (56.4%), and viability (57.2%) (P<0.05). Moreover, temperature-dependent declines were observed in certain kinetic parameters such as VCL and ALH. These findings suggest that goat spermatozoa are sensitive to temperature changes, with 33°C providing a more favorable microenvironment for physiological function. Furthermore, thermotaxis may serve as a potential biological marker for sperm selection in assisted reproductive technologies.