The in vitro addition of docosahexaenoic acid (DHA) improves the quality of cooled but not frozen-thawed stallion semen

The aim of this study was to assess the effect of the addition of docosahexanoic acid (DHA) on the in vitro quality of cooled and frozen-thawed stallion semen. In Experiment 1, semen from 10 stallions was collected (3 ejaculates per stallion). Semen was diluted to 100 x 106 spermatozoa/mL with 0.02 mM of vitamin E (VE) and 0, 1, 10 or 20 ng of DHA/mL and frozen. Semen was thawed and total motility (TM), acrosome integrity and morphology were assessed. In Experiment 2, semen from 3 stallions was collected (3 ejaculates per stallion) and frozen as in Experiment 1, but VE and DHA were added after thawing. Total motility and progressive linear motility (PLM) were assessed at 30, 60 and 120 min and viability, acrosome integrity and membrane fluidity at 30 min. In Experiment 3, semen from 5 stallions was collected (1-3 ejaculates per stallion), diluted to 20 x 106 spermatozoa/mL and stored at 4ºC. After 1, 24, 48 and 72 h, TM, PLM, viability, membrane fluidity and lipid peroxidation were assessed. The addition of DHA had no effect on frozen semen (Experiments 1 and 2) but improved TM, PLM and membrane fluidity in cooled stallion semen.