Effect of L-Carnosine Supplementation to the Freezing Extender on the Post-Thaw Quality of Canine Epididymal Spermatozoa

Cryopreservation of epididymal spermatozoa is a useful tool for conserving the genetic material of dogs of high breeding value. However, spermatozoa harvested from the cauda epididymis are more susceptible to cryoinjury than ejaculated sperm due to the presence of a cytoplasmic droplet and the absence of protective seminal plasma. L-carnosine is a naturally occurring dipeptide with antioxidant properties, and its potential for supplementing freezing extenders is currently being investigated. The study assessed how L-carnosine (0.5, 1, 5, 10 mM) addition to the extender affects the post-thaw quality of canine epididymal spermatozoa. The following sperm parameters were analyzed: total motility (TMOT), progressive motility (PMOT), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, and malondialdehyde (MDA) concentration. An analysis of thawed spermatozoa revealed that extenders supplemented with higher concentrations of L-carnosine induced a decrease in the values of TMOT, PMOT, ATP content, PMI, and MMP. Although the addition of L-carnosine reduced MDA levels, the antioxidant effect didn’t lead to an improvement in the post-thaw functional parameters of canine spermatozoa. Data suggests that the effect exerted by L-carnosine may be attributed to its potential influence on vital bioenergetics metabolic pathways of canine spermatozoa. The study proved that L-carnosine supplementation does not improve the post-thaw quality of canine epididymal sperm. Results indicate a need for further research on extender formulations that combine antioxidant protection with the preservation of sperm metabolic activity.