decreases digestibility of the proteins. The inclusion of a good quality protease in the diet can reduce the impact of trypsin inhibitors on digestion.


• A coarser particle size of soybean meal, close to 700- 900 μm, favours better digestion of soybean protein and minimises the negative effects of antitrypsin factors.


• A high soluble non-starch polysaccharide (NSP) content in the feed can increase viscosity in the gut, thereby reducing the feed passage rate in the stomach (digesta). This leads to decreased absorption of digesta and an increased inci- dence of wet droppings. The addition of an exogenous NSP enzyme to feed can considerably reduce NSP levels and the risk of bacterial enteritis.


• Mycotoxins can alter normal gut functions, such as the bar- rier function and nutrient absorption. As far as feed stor- age is concerned, control measures need to be implement- ed to minimise grain damage and conditions that could increase mould and insect spoilage. Adding a broad-spec- trum mycotoxin binder to the diet can help reduce the adverse effects of mycotoxins on poultry health.


• Rancid oils and fats should be rejected since they have been shown to lead to enteric diseases. Proper storage conditions in tanks and transport lines should be checked frequently to prevent rancidity developing in the feed mill. Additionally, the use of antioxidants in feed can help reduce oxidation and thus reduce rancidity.


• Certain feed ingredients and additives have been shown to modulate gut microbiota and the immune system in poul- try. These dietary factors should be considered when for- mulating broiler diets (Figures 1 and 2). Several classes of feed additives have been proposed and evaluated for poul- try preproduction, including organic acids, essential oils, probiotics, prebiotics, enzymes and trace minerals. These feed supplements may be used as an alternative to antibi- otic growth promoters to modulate gut microbiota and en- hance gut integrity for better growth, feed efficiency and bird health (Figure 2).


Water quality Water is the most important nutrient for poultry and is in- volved in every physiological process of a bird. Water is also a medium that can transport bacterial, viral and protozoan in- fections in poultry houses. Unfortunately, the importance of water quality is often overlooked. Water quality is essential for proper digestion, so its physico-chemical properties should be measured, controlled and improved on the farm. Water pH is an important factor that can influence microbial populations in water and in the animal’s gut, thus maintain- ing microbiota balance in the lumen environment. The ideal water pH for poultry should be 5-7, because an alkaline pH (above 7) is shown to reduce the activity of digestive en- zymes. Studies show that birds can tolerate a low pH of 3.5. Drinking water with carbonates and other salts that increase


Figure 1 - The vicious cycle of poor gut health.


• Poor feed hygiene • High level of NSP • Mycotoxins • Rancid fats and oils • Antinutritive factors • Poor water hygiene • Coccidiosis • Viruses, etc.


Poor feed and water quality, coccidiosis, viruses, etc.


Disbalance of gut microbiota


• Presence of predisposing factors that cause microbiota imbalances in lumen environment


Poor digestion and


• Poor gut health


absorption of nutrients


Alternation in gut integrity


• Inflammation and oxidation caused by interference of microbiota with mucosa


Figure 2 - Nutritional strategies to improve gut health in antibiotic free production


• Mycotoxin binder, • antioxidants, • organic acids • (feed acidifier, • water acidifier)


Good quality feed and water


Optimising gut microbiota


• Encapsulated organic acids, coated essential oils, probiotics, prebiotics


Optimising digestion


• Exogenous enzymes


absorption of nutrients


Improving gut integrity


• Chelated trace minerals (Zn,Cu,Mn),


• encapsulated organic acids


alkalinity and hardness can cause problems. Hardness and an alkaline water pH create an environment for biofilm and en- dotoxins to thrive in the water tank, pipeline and drinker due to the proliferation of algae and microbes.


Combination of measures To optimise feed digestibility and performance in antibiotic- free poultry production, it is necessary to develop cost- effective alternative strategies to manipulate gut microbiota. Several feed additives – including organic acids, essential oils, probiotics, prebiotics, exogenous enzymes and trace miner- als – have been successfully used for better gut health and more efficient production in poultry. Combinations of these various alternatives, along with proper farm management and biosecurity measures, are the key to maximising poultry performance in this antibiotic-free era.


References available on request. ▶ POULTRY WORLD | No. 2, 2021 37


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