Influence of omega‐3 incorporation in sperm preservation medium on physical and kinematic properties of chilled and cryopreserved ram spermatozoa

Abstract

Two experiments were carried out to investigate the efficiency of supplementing sperm preservation medium with omega-3 polyunsaturated fatty acids on improving liquid-chilled storage and cryopreservation capacity of ram spermatozoa. Ejaculates (n=100) were collected from five adult rams, Ovis aries, by an artificial vagina twice weekly throughout the period February-April, 2017. After initial evaluation, ejaculates of each collection session from the same males were pooled, diluted (1:10) with Tris-citric acid egg yolk extender, and were further split into five aliquots using a split-sample technique. The first aliquot served as control (omega-free), whereas the other four portions were supplemented with 0.1, 0.2, 0.3 or 0.4mM omega-3, respectively (T0 ). Thereafter, the diluted specimens were stored at 4°C for 48hr, during which sperm physical and morphometric properties were evaluated along with oxidative stress indices (T24 , T48 ). Omega-3 levels that efficiently mitigated the detrimental effects of chilled preservation, and maintained preservation aptitude of spermatozoa were further investigated for sperm cryosurvival against control (untreated). Post-thaw physical and kinematic properties of spermatozoa, in all groups, were objectively evaluated by a computer-assisted sperm analysis (CASA) system. The results showed that, at 48hr of chilled storage, supplementing preservation medium with 0.4mM omega-3 was positively correlated (p<0.01) with each of progressive motility, live sperm, intact acrosome and intact cell membrane (r=0.83, 0.85, 0.85, 0.89, respectively). Furthermore, a positive correlation (p<0.01) was observed between inclusion of omega-3 in cryopreservation medium and each of post-thaw total sperm motility, progressive motility, live sperm, normal sperm, intact acrosome, intact cell membrane, VCL, VSL, VAP, ALH and STR (r=0.76, 0.84, 0.79, 0.90, 0.89, 0.91, 0.61, 0.73, 0.65, 0.78 and 0.60, respectively). These results accentuate efficiency of supplementing the diluent with omega-3 fatty acids on improving chilled and cryopreservation aptitude of ram spermatozoa.