Plant Extracts, Energy, and Immune Modulation in Broilers

This chapter presents information obtained from experiments involving male Ross 308 broiler chickens on the effects of a standardised combination of plant extracts (PE) including carvacrol, cinnamaldehyde and capsicum oleoresin, on bird performance, hepatic antioxidant concentration and immunomodulation. Birds were reared under industry-recognised environments and were fed one of four diets. There were two control diets based on either wheat or maize, formulated to be iso-energetic and iso-nitrogenic. The other two diets were the control diets supplemented with 100 g per tonne of PE, respectively. Feeding PE improved dietary feed efficiency, dietary net energy and hepatic antioxidant contents of the birds, but did not change dietary metabolisable energy (ME). Overall, feeding PE reduced the mRNA transcript levels of three cytokines (IL-12B, IFN-G, and IL-6) and the marker CD 40 LG in caecal tonsils. Dietary PE may maximise the nutritional value of feed through improving gut health by reducing intestinal inflammation. Their mode of action is associated with improved dietary energy availability, immune status and hepatic antioxidant contents of the birds. However, studies that have focused solely on the effect of PE on ME alone may not have detected their full benefit to improve the efficiency of broiler meat production.