Effect of Melatonin Supplementation to Tris-Egg Yolk and Skim Milk Extenders on Sperm Kinematics of Buck Semen During Summer Storage

The study evaluated the effect of melatonin supplementation to tris-fructose-egg yolk and skim milk-based extenders on sperm kinematics of Bidri buck semen stored at 4°C during summer. Six ejaculates were collected from each of five adult Bidri bucks at twice weekly intervals. On each occasion, semen samples were pooled, extended in tris-fructose-egg yolk (TEYF) or skim milk (SMF) extenders with 0.2 mM (M1) or 0.3 mM (M2) melatonin or without melatonin and stored for 72 h. Computer-assisted semen analysis (CASA) was used to assess sperm kinematics at 0, 24, 48 and 72 h. Curvilinear velocity (VCL), average path velocity (VAP) and straight line velocity (VSL) decreased progressively in all extenders, with TEYF extenders maintaining significantly (P<0.05) higher velocities than SMF extenders. TEYFM1 showed the most consistent protection at 24 to 48 h. Linearity (LIN), straightness (STR) and wobble (WOB) declined with time, but melatonin, TEYFM2, attenuated this reduction at later intervals. Beat cross frequency (BCF) and amplitude of lateral head displacement (ALH) decreased during storage, although TEYF-based extenders and melatonin-supplemented treatments maintained higher values than controls. In conclusion, melatonin supplementation at 0.2 mM in TEYF extender provided superior protection against storage-related decline in sperm kinematics of Bidri buck semen stored at 4°C during summer.