Reducing the dietary omega-6 to omega-3 polyunsaturated fatty acid ratio attenuated inflammatory indices and sustained epithelial tight junction integrity in weaner pigs housed in a poor sanitation condition

The present study was conducted to determine the effect of reducing dietary n-6:n-3 PUFA ratio on the performance, inflammatory response and gut morphology of PWD challenged with sanitary and poor sanitary conditions in weaned pigs, and to test the hypotheses that (1) exposure to an poor sanitary environment will increase indices for inflammatory response" and (2) reducing n-6:n-3 PUFA ratio in diets for weaned pigs will attenuate the inflammatory response induced by the environmental challenge. A total of 108 male pigs [Duroc × (Yorkshire × Landrace)" initial BW 7.1 ± 0.5 kg] weaned at 21 days of age were randomly allocated to one of 3 dietary treatments and 2 environmental conditions (sanitary vs. poor sanitary) to give 6 replicate pens per treatment with 3 pigs per pen. The dietary treatments were 3 graded levels of n-6:n-3 PUFA ratio (i.e.,20:1, 10:1 and 4:1) formulated using tallow, safflower oil, and a vegetable and fish oil blended product. One pig per pen (n = 6) was euthanized on d 0, d 7 and d 14, to collect blood and small intestinal tissue samples. Pigs exposed to a poor sanitary environment tended (P < 0.10) to grow more slowly and utilized feed less efficiently (P < 0.05) compared with the pigs housed in sanitary conditions. Housing weaned pigs in a poor sanitary environment increased (P < 0.05) the incidence of diarrhoea. Furthermore, a poor sanitary environment increased (P < 0.001) the occludin diffusion in the ileal epithelium of weaned pigs and increased plasma concentrations of TNF-α (P < 0.05), COX-2 (P < 0.05), PGE2 (P < 0.01) and LTB4 (P < 0.05) on d 14. Reducing the n-6:n-3 PUFA ratio improved (P < 0.05) both ADG and FCR but reduced (P < 0.01) the incidence of diarrhoea over 14 days after weaning, and they tended to attenuate (P < 0.10) the diffusion of the transmembrane tight junction protein occludin at the apical intercellular region of the ileal epithelium. Moreover, reducing the n-6:n-3 ratio in the diet attenuated the increased inflammatory indices induced by the environmental challenge. Correlation analysis indicated that n-6 PUFA intake of individual pigs positively correlated with plasma concentrations of IL-1β (P < 0.01), TNF-α (P < 0.05), PGE2 (P < 0.01) and COX-2 (P < 0.05). Our results indicated that housing pigs in a poor sanitary environment after weaning increased inflammatory responses and reduced growth performance. Reducing the n-6:n-3 PUFA ratio to 4:1 attenuated the inflammatory responses observed after weaning in both environment on d 7 and in the poor sanitary environment on d 14.