Effects of dietary n-6/n-3 PUFA ratio on growth performance and lipid metabolism in nursery pigs

The proportion of n-6 and n-3 polyunsaturated fatty acid (PUFA) in commercial pig feed is severely unbalanced. This study was conducted to investigate the effects of different n-6/n-3 PUFA ratios on growth performance and lipid metabolism of nursery pigs. A total of 240 nursery pigs (Duroc × Large White × Landrace) were fed diets with different n-6/n-3 PUFA ratios, including 10:1, 5:1, 3:1, and 1.5:1. Pigs fed diet with n-6/n-3 PUFA ratio of 1.5:1 or 3:1 had optimum average daily gain and feed to gain ratio (<i>p</i> < 0.05). The levels of serum lipids including total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein were the lowest in pigs fed diet with n-6/n-3 PUFA ratio of 1.5:1 (<i>p</i> < 0.05). The concentrations of serum insulin, adiponectin and leptin were the highest in pigs fed diet with n-6/n-3 PUFA ratio of 3:1 (<i>p</i> < 0.05). Pigs fed diet with n-6/n-3 PUFA ratio of 3:1 had the highest abundance of genes associated with fatty acid absorption and transportation (<i>FATP4</i>, and <i>PPARγ</i>), synthesis and storage (<i>FAS</i> and <i>GPAT</i>) and degradation (<i>ATGL</i>, <i>HSL</i>, and <i>MAGL</i>) in intestine (<i>p</i> < 0.05). Pigs fed diet with n-6/n-3 PUFA ratio of 1.5:1 had the lowest abundance of genes associated with fatty acid absorption (<i>CD36</i> and <i>FABP4</i>), synthesis and storage (<i>ACC</i>, <i>FAS</i>, <i>ACLY</i>, <i>PAP</i>, <i>AGPAT</i>, and <i>GPAT</i>) and degradation (<i>CPT1</i> and <i>HSL</i>) in gastrocnemius muscle (<i>p</i> < 0.05). The mRNA expression of genes associated with fatty acid metabolism (<i>FATP2</i>, <i>FATP5</i>, <i>FABP1</i>, <i>FABP4</i>, <i>LPL</i>, <i>ACS</i>, <i>ACLY</i>, <i>AGPAT</i>, <i>GPAT</i>, <i>CPT1</i>, <i>ATGL</i>, and <i>MAGL</i>) was up-regulated in liver and subcutaneous fat of pigs fed diet with n-6/n-3 PUFA ratios of 1.5:1-5:1 (<i>p</i> < 0.05). In summary, diets with lower n-6/n-3 PUFA ratios improve growth performance, reduce blood lipids, facilitate lipid metabolism in intestine, liver and subcutaneous fat, and inhibit fatty acid absorption, synthesis and storage in gastrocnemius muscle in pigs.