Effects of dietary inclusion levels of palm oil on growth performance, antioxidative status and serum cytokines of broiler chickens

This study was conducted to investigate the effects of dietary palm oil inclusion levels on growth performance, serum antioxidative status and cytokines in Sanhuang broiler chickens. A total of 208 one-day-old female Sanhuang chickens were randomly allocated to four treatment groups with four replicates per group and of 13 birds each for a 42-day feeding trial. Dietary treatments were basal diet without palm oil (control) and diets containing 2%, 4% or 6% palm oil. During days 22 to 42 and the overall experimental period, chickens fed diets supplemented with 4% and 6% palm oil had a lower average daily feed intake (ADFI) (p = 0.019) and feed to gain ratio (F/G) (p = 0.031). Average daily gain (ADG) tended to be higher (p = 0.089) for palm oil inclusion treatments compared with the control treatment from days 1 to 42. Dietary 2% and 4% palm oil treatments significantly lowed serum malondialdehyde concentration on day 21 when compared to the control and 6% palm oil treatments (p = 0.027). Dietary 6% palm oil treatment significantly reduced the catalase (CAT) activity (p = 0.018) and total antioxidant capacity (T-AOC) (p = 0.027) in serum in comparison with the control treatment on day 21. No significant differences were observed in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in serum among dietary treatments on day 21. There were no significant differences in T-AOC, CAT, SOD and GSH-Px activities among dietary treatments on day 42. Dietary inclusion of 4% and 6% palm oil significantly increased (p = 0.01) serum interleukin-1β (IL-1β) content, but improved transforming growth factor-β (TGF-β) content in serum on both days 21 and 42 (p = 0.032 and 0.022 respectively) as well as IL-10 content on day 42 (p = 0.022) when compared with the control treatment. Furthermore, dietary inclusion of 6% palm oil significantly reduced tumour necrosis factor-α (TNF-α) content on days 21 and 42 (p = 0.021 and 0.001 respectively) compared with the control treatment. These results suggest that dietary inclusion of 4% and 6% palm oil could improve the growth performance, modulate the balance between pro- and anti-inflammatory cytokines, and show limited effect on antioxidative status in Sanhuang broiler chickens.