Melatonin in semen extender did not improve quality of frozen-thawed feline sperm

We evaluated impacts of melatonin addition to a tris-egg-yolk (TEY) semen extender on sperm quality after freezing cat semen. Sperm was obtained via urethral catheterization (UC) after medetomidine treatment and epididymal slices (ES) in 10 cats. Samples were frozen after dilution in a TEY extender with melatonin (2 or 3 mM) or without melatonin (control). Sperm quality was assessed before and after freezing. In raw semen, sperm progressive motility (PM) was greater (p = 0.004) in samples obtained by ES than by UC. Sperm PM, vigor and sperm with preserved membrane function significantly decreased in frozen-thawed samples compared to raw semen, without significant differences between collection methods. In postthaw UC samples, no significant differences were observed between control and melatonin (2 and 3 mM) groups, being the overall means as follows: sperm PM: 29.4%, sperm membrane function: 40.8%; sperm with condensed chromatin: 92.5 %, and live acrosome-intact sperm: 28.9%. In postthaw ES samples, no significant differences were observed between control and melatonin (2 and 3 mM) groups, being the overall means as follows: sperm PM: 36%; sperm membrane function:42%; sperm with condensed chromatin: 86%; and live acrosome-intact sperm: 32%. In conclusion, supplementation of the extender with melatonin (2 mM or 3 mM) did not improve sperm quality after freezing in cats.