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The Dietary Omega-6 to Omega-3 Fatty Acid Ratio Impacts the Inflammatory Response in Nursery Pigs More Than Increasing Omega-3 Intake
The objective of this experiment was to determine if the intake of omega (ω)-3 fatty acids affects the inflammatory response of nursery pigs post-weaning, and if this response depends on the ratio with ω-6 fatty acids. Individually housed, newly weaned pigs (26 ± 2 days of age; n = 100) were assigned to one of five diets and one of two inflammatory challenge groups arranged as a 5 x 2 factorial with repeated measures. Diets consisted of a control (Con; 10:1 ω-6:ω-3, 3.5% total fat, tallow based), 3 diets with 3.5% fat (plant based) and ω-6:ω-3 ratios of 10:1, 5:1 or 1:1 (3.5/10, 3.5/5 and 3.5/1 respectively), and a 10:1 ratio diet with 5% total fat (5/10). This allowed for the comparison of increasing ω-3 intake at a constant ratio (10:1 ratio; 3.5% vs 5% fat) and decreasing ratio at a constant ω-3 intake (3.5% fat; 10:1, 5:1 and 1:1 ratios). Challenge groups consisted of a saline or LPS (15 µg/kg BW E. Coli lipopolysaccharide) injection. Pigs were fed their assigned diets for 22 d prior to the 24 h inflammatory challenge on d 23. Rectal temperatures were measured hourly for the first 6 h, then at 12 and 24 h post-injection. Blood samples were collected at 0, 2, 6 and 12 h post-injection. ADG and ADFI from d 0 to 22 or during the challenge period were unaffected by diet (P > 0.05). During the challenge, LPS pigs had lower (P < 0.01) ADFI (0.93 vs 0.40 kg, saline vs LPS) and ADG (+0.44 kg vs -0.52 kg, saline vs LPS). Rectal temp, BUN, IL-1β, IL-6 and TNFα were unaffected by diet (P > 0.05), but were increased by LPS (P < 0.01). Serum IL-8 concentration was reduced with decreasing ω-6:ω-3 ratio (16.79 vs 11.14 pg/ml, 10:1 vs 1:1; P = 0.03) but was unaffected by dietary ω-3 amount at a constant ratio (P > 0.05). Pigs consuming the 3.5/1 diet had lower IL-8 responses relative to those consuming the 3.5/10 and 3.5/5 diets (diet × challenge P = 0.03). Additionally, the IL-8 response of pigs fed the 1:1 diet and challenged with LPS was similar to the saline injected pigs fed the 10:1, 5:1 or 1:1 diets (P > 0.05), indicating that reducing the dietary ω-6:ω-3 ratio impacts a piglets inflammatory response post-weaning.
Keywords: Swine, Omega-3, Inflammatory Response