Effect of supplementing ram semen extender with melatonin on oxidative stress indices and physical properties of chilled spermatozoa

Abstract

The current study aimed to evaluate the efficiency of supplementing ram semen extender with melatonin on chilled storage capacity of spermatozoa. Eighty ejaculates were collected from 5 Barki rams, 16 ejaculates each, using an artificial vagina throughout the period from January – February, 2017. The ejaculates of each collection session were pooled and diluted (1:10) with Tris-citric egg yolk extender, and were split into 4 aliquots. The first portion served as control (melatonin-free), whereas the other 3 portions were supplemented with 0.1, 0.2 or 0.3 mM melatonin. Thereafter, the samples were stored at 4 oC for 48 hrs, during which sperm physical and morphological properties were evaluated at 24 hr interval. Simultaneously, oxidative stress indices in terms of total antioxidant capacity (TAC), malondialdehyde concentration (MDA), resazurin reduction test, in addition to enzymatic activities of AST, ALT and ALP were determined. The results revealed that, over the 48 hr preservation period, level of melatonin in the diluent was positively correlated (P<0.01) with sperm motility, viability, percent of normal sperm, intact acrosome, sperm cell membrane integrity and total antioxidant capacity (r= 0.75, 0.96, 0.82, 0.95, 0.96 and 0.74, respectively). Contrarily, a negative correlation (P<0.01) was observed between melatonin level and each of primary and secondary sperm abnormalities, MDA, AST, ALT and ALP over time of storage (r= – 0.71, – 0.85, – 0.46, – 0.71, – 0.95 and – 0.84, respectively). These results elucidate that supplementing the diluent with 0.3 mM melatonin efficiently reduced oxidative stress and improved chilled storage of ram spermatozoa.