Abstract
Typical formulated broiler diets are deficient in n-3 poly-unsaturated fatty acids (PUFA) due to widening n-6:n-3 PUFA ratio which could greatly affect performance, immune system of birds and, more importantly, meat quality. This study was conducted to evaluate the effect of modifying dietary n-6:n-3 PUFA ratio from plant and animal oil sources on performance, behavior, cytokine mRNA expression, antioxidative status and meat fatty acid profile of broiler chickens. Birds (n = 420) were fed 7 diets enriched with different dietary oil sources and ratios as follows: sunflower oil in control diet (C); fish oil (FO); 1:1 ratio of sunflower oil to FO (C1FO1); 3:1 ratio of sunflower oil to fish oil (C3FO1); linseed oil (LO); 1:1 ratio of sunflower oil to linseed oil (C1LO1); 3:1 ratio of sunflower oil to linseed oil (C3LO1), resulting in dietary n-6:n-3 ratios of approximately 40:1, 1.5:1, 4:1, 8:1, 1:1, 2.5:1 and 5:1, respectively. The best final body weight, feed conversion ratio as well as protein efficiency ratio of broilers were recorded in the C1FO1 and C1LO1 groups. Compared with the control group, the dressing percentage and breast and thigh yield were highest in the C1FO1 and C1LO1 groups. Narrowing the dietary n-6:n-3 ratio increased (P < 0.05) n-3 PUFA content of breast meat. Moreover, the breast meat contents of eicosapentaenoic acid and docosahexaenoic acid increased (P < 0.05) with increasing dietary FO whereas α-linolenic acid content was higher with LO supplementation. Also, enriching the diets with n-3 PUFA from FO and LO clearly decreased (P < 0.05) serum total cholesterol, triglycerides and very low-density lipoproteins and enhanced antioxidative status. The feeding frequency was decreased (P < 0.05) in the C1FO1 and C1LO1 groups. Likewise, n-3 PUFA-enriched diets enhanced the frequency of preening, wing flapping and flightiness. Animal oil source addition, compared to plant oil, to broiler diets enhanced the relative mRNA expression of interferon gamma, interleukin-1 beta, interleukin-2 and interleukin-6 genes, especially at low n-6:n-3 ratios. This study has clearly shown that narrowing n-6:n-3 ratio through the addition of FO or LO improved performance and immune response of broilers and resulted in healthy chicken meat, enriched with long chain n-3 PUFA.