Background: This study was conducted to evaluate the potential protective effects of omega-3 poly unsaturated fatty acids (PUFAs) on bovine sperm quality in response to cooling and cryopreservation. Materials and Methods: Ejaculates from 5 proven fertile bulls were allocated to control and 4 experimental groups. Group 1: polyethylene glycol (PEG, as a solvent) was added alone to the extender, groups 2, 3 and 4: different concentration of omega-3 PUFAs (1, 2.5 and 5%) in combination with PEG were added to the semen extender. Motility (using Computer Aided Sperm Analysis: CASA), viability and morphology were investigated in 3 conditions: after 24 and 48 hours cold liquid storage or frozen-thawed. Results: Results showed that PEG has some detrimental effects on sperm quality. Cooling as well as cryopreservation significantly decreased most of measured variables of sperm compared with fresh semen, whereas treatments did not improve sperm quality. Furthermore, some variables were decreased significantly in treatments (P < 0.05). Conclusion: Addition of Ω-3 PUFAs to semen extenders cannot be effectively introduced to conservation media as well as sperm membrane to protect spermatozoa in response to cooling and freezing. It can be suggested if Ω-3 PUFAs supplemented to the diet of bulls in order to modify the fatty acid compositions of sperm they might perform their preventive properties.

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