Effect of reducing dietary ratio of the omega-6 and omega-3 essential fatty acids on milk production and ovarian performance in fresh Holstein dairy cows

This study was conducted to investigate the effect of reducing dietary ratio of omega-6/omega-3 essential fatty acid (EFA) on dry matter intake, yield and milk composition, ovarian performance and blood concentrations of estradiol and progesterone using 24 multiparous Holstein cows. Experimental treatments including different n-6 to n-3 EFA ratio; namely, 2.5, 4.5, or 6.5 parts of n-6 to 1 part of n-3 EFA. Dry matter intake and milk yield of cows were recorded daily. Also, body condition score and milk composition were recorded and ovarian activity was monitored by transrectal ultrasound scanning. Dry matter intake and milk composition were not affected by treatments. Daily milk yield was significantly higher in low and medium n- 6/n-3 FA ratio diets in comparison to high diet (P<0.05). Cows assigned to high n-6/n-3 FA ratio diet had greater plasma Haptoglobin concentrations compared to other diets (P<0.05). Results indicated that number of large follicles was greater in medium diet than high diet (P<0.05). Progestrone concentration was significantly decrease in high diet treatment (P<0.05). Results of this study indicate that modulating dietary n-6/n-3 FA ratio could lead to a higher milk yield and improve ovarian performance in fresh cows.