Inflammation and immune activity cost energy

The gut is a highly complex ecosystem in which commensals and pathogens live in dynamic antagonistic interactions competing for the same niches and substrates. Any alterations in these relationships may lead to inflammatory reactions, gastrointestinal or systemic infections – in any event, to energy-consuming imbalances.


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500 45 0 0 45 224 225 10 20 day of trial 38 ▶ POULTRY WORLD | No. 3, 2021 30 40 50 PC

he intestinal tract is the largest immune organ with the most extensive contact surface between the environment and body. It comprises cells of the immune system as well as a huge number of

microbes – the microbiota – which produce metabolites and vitamins. In homeostasis (or eubiosis), this system maintains host health by optimising beneficial symbiotic re- lationships. For the host it is necessary to prevent transloca- tion of commensal and pathogenic micro-organisms across the mucosal barrier of the gut – that’s the mission of the gut immunity.

Figure 1 - Curves of weight development for the AGP supplemented group (PC) and the wood lignan supplemented group (NC + wood lignans) show the clear difference in performance development.

NC + ROI 2464 1968 1003 660

2672 3177

Microbial community The gastrointestinal tract houses a dynamic and complex ecosystem. It is influenced by the microbial community, the composition and physical structure of the diet, as well as the age and health status of the bird. All these factors influ- ence each other. Together they have their impact on the health and performance of the animal. Bacterial colonisa- tion of the GIT in chickens starts with hatching. First, the caeca are colonised by streptococci and enterobacteria. Within the first day of life, bacteria spread throughout the digestive tract. The composition of the intestinal flora changes with age. Bacterial density in the duodenum is low due to the short transit time, low pH and dilution by diges- tive juices. The environment for bacterial growth is more fa- vourable in the jejunum. The greatest bacterial density is found in the caeca. The small intestine is the site of enzymatical digestion. Pro- teins and carbohydrates that escape digestion in the small intestine are metabolised by the commensal microbiota in the hindgut. In general, fermentation of undigested carbo- hydrates (fermentable dietary fiber) is associated with ben- eficial effects: hindgut bacteria use fermentable fiber as an energy source and primarily produce short-chain fatty acids (SCFA) as metabolites. SCFA have favourable effects on the composition of the gut flora, help to prevent colonisation by pathogens, are absorbed by the bird and used as an en- ergy source, while butyrate is important for the health and integrity of the gut mucosa.

Protein fermentation An excess of protein or an undersupply of fermentable feed components increases protein degradation by the gut flora of the hindgut. The composition of the intestinal flora shifts towards proteolytic bacteria. Protein fermentation produces ammonia and biogenic amines. Ammonia is a strong cyto- toxin that damages the mucosa of the intestine and causes inflammation. It also passes easily into the bloodstream and stresses all organs. Protein fermentation is associated with inflammatory bowel disease in humans, with post-weaning

body weight, g


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