Effects of dietary n-6:n-3 fatty acid ratio and vitamin E on semen quality, fatty acid composition and antioxidant status in boars

• Dietary PUFA affects semen quality, fatty acid composition and lipid peroxidation.
• It is important to account for the n-6:n-3 ratio when formulating diets to avoid potential negative effects.
• Dietary vitamin E has dose effect on the sperm motility and antioxidant status.

The aim of the present study was to evaluate the effects of dietary n-6:n-3 fatty acid (FA) ratio and vitamin E on the semen quality, FA composition and antioxidant status of boars. Forty-eight Landrace boars were randomly distributed in a 3 × 2 factorial design with three n-6:n-3 FA ratios (14.4, 6.6 and 2.2) by the inclusion of three oil sources (soybean, fish/soybean, fish) and two vitamin E levels (200 and 400 mg/kg). During the 8 weeks of treatment, semen parameters were evaluated. Serum, sperm and seminal plasma samples were taken at 0 and 8 weeks to monitor the FA composition and antioxidant status. Results showed that the 6.6 and 2.2 dietary ratios very effectively increased docosahexaenoic acid (DHA) and n-3 polyunsaturated fatty acid (PUFA) and decreased docosapentaenoic acid (DPA) and n-6:n-3 ratio in spermatozoa. The 6.6 dietary ratio contributed to a greater progressive sperm motility (P < 0.05) than the 14.4 and 2.2 dietary ratio, and this ratio also enhanced the superoxide dismutase (SOD) and total antioxidant capacity (TAC) (P < 0.05) in seminal plasma more significantly than the other two ratios at week 8. Compared with 200 mg/kg supplementation of vitamin E, 400 mg/kg supplementation of vitamin E increased the progressive sperm motility, SOD of sperm, TAC and SOD of seminal plasma and serum, and decreased sperm malondialdehyde (MDA) (P < 0.05). In conclusion, the 6.6 dietary ratio and 400 mg/kg vitamin E supplementation improve progressive sperm motility by modifying the sperm FA composition and antioxidant status.