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 ( p 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 ( p 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 ( p 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 ( FATP4 , and PPARγ ), synthesis and storage ( FAS and GPAT ) and degradation ( ATGL , HSL , and MAGL ) in intestine ( p 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 ( CD36 and FABP4 ), synthesis and storage ( ACC , FAS , ACLY , PAP , AGPAT , and GPAT ) and degradation ( CPT1 and HSL ) in gastrocnemius muscle ( p 0.05). The mRNA expression of genes associated with fatty acid metabolism ( FATP2 , FATP5 , FABP1 , FABP4 , LPL , ACS , ACLY , AGPAT , GPAT , CPT1 , ATGL , and MAGL ) 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 ( p 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.