A historical perspective change toward dietary fiber in poultry nutrition has recently taken place. Fiber was previously considered a non-digestible and energy-diluting dietary component that can negatively impact poultry digesta viscosity and gut function. Recent studies have confirmed the beneficial effects of fiber in poultry nutrition, and, optimizing the content of this previously ignored and mysterious poultry diet component is an essential aspect of formulating diets for laying hens. Fiber type and amount of fiber should be optimized to get the most benefit. This series of articles will introduce you to the definition of fiber, its sources, types, and the role of fiber in laying hens’ nutrition.
What is fiber?
Fiber is the consumable parts of plants that are resistant to digestion and absorption in the small intestine and might be partially or entirely fermented in the hindgut. More specifically, fiber is an intrinsic component in plant-based feed ingredients, and its amount, structural type, digestibility, and solubility vary depending on the origin.
Types of fiber in feed ingredients
Insoluble fiber usually refers to the plant cell wall components that comprise cellulose, hemicelluloses, and a complex oxygen-containing organic polymer known as lignin. These components are resistant to enzymatic digestion in the poultry gut and pass through the digestive tract relatively intact. Even though insoluble fiber acts as an inert substance, it can be beneficial from the following perspectives:
- Increase in starch digestibility in the gut
- Improvement in gut functions with a positive effect on gizzard function
- Stimulate intestinal villi development with a positive impact on nutrients digestion and absorption
- Increase in passage rate in the gut and subsequently increase in feed intake
- Increase in dry matter content of the feces and subsequently a reduction in ammonia production and improvement in litter and air quality
Soluble fiber contains compounds (pectin, beta-glucans, xyloglucans, mannans, and arabinoxylans) that trap water and increase the viscosity of the digesta. The increase in digesta viscosity can reduce the passage rate in the gut and compromise the digestion and absorption of starch, protein, and fat. That being said, soluble fiber can benefit the function and development of the gut and immune system.
Fiber sources in poultry nutrition
Some common fibrous feed ingredients in layer nutrition include alfalfa meal, barley hulls, Distiller’s dried grains with solubles (DDGS), oat hulls, sugar beet pulp, rice hulls, wheat bran, all by-products of cereal processing for food use such as brans and middling, and by-products of oil extraction from oil seeds such as sunflower seed or rapeseed. Researchers at Wageningen University recently studied the effect of fresh brewers’ grains (beer byproduct) on broiler chick nutrition and observed higher feed intake and body weight gain compared to the control group (personal communication). The study’s promising results might be related to the effects of fiber on birds’ performance. In addition to fibrous feed ingredients, fiber products of lignocellulose have been studied as a novel insoluble fiber source in poultry diets (Rohe and Zentek, 2021). Fibrous feed ingredients usually have low amounts of energy, so the dietary inclusion rate of oil might need to increase to compensate for those ingredients, which might create new problems (read on to find out more about these problems). Given that the fiber products of lignocellulose contain standardized levels of crude fiber and their dietary inclusion level is low, they would not dilute the dietary energy content. These products are mycotoxins-free, whereas some fibrous feed ingredients might contain molds and mycotoxins.
Strategies to overcome potential technical problems associated with increasing dietary fiber
Adding fibrous ingredients to poultry diets typically dilutes dietary energy content; this is often compensated by adding additional oil to the diet. High levels of oil (for example, soy oil) in diets can create handling problems due to high moisture content and nutritional limitations. Appropriate strategies are needed to overcome these issues. Oil seeds are great sources of energy and fiber. To avoid oil overuse in diets with high fiber levels, it is recommended to supply part of the dietary energy using oil seeds such as sunflower, rapeseed, canola, etc., in these diets.
Increasing dietary fiber might increase soluble fiber levels, increasing digesta viscosity and reducing nutrient digestion and absorption. Using Non-Starch-Polysaccharides-degrading enzymes in such diets help to mitigate the problem. According to their matrix value, these enzymes can increase dietary nutrients and energy availability. The increase in dietary energy release by NSP degrading enzymes in wheat-based diets can be up to 3 to 6%, thus reducing the energy deficit from adding fiber. It is imperative to precisely include the matrix value of commercial enzymes in feed formulation. Please refer to our previous article to review the feed formulation considerations while including commercial enzymes in poultry diets.
In summary, fiber type and inclusion level should be optimized in the laying hens’ diet without compromising bird performance and the dietary energy and nutrient balance. Stay tuned for the second part of this article in our next newsletter issue to discuss this further!
References
Desbruslais, A., Wealleans, A., Gonzalez-Sanchez, D., and M. di Benedetto. 2021. Dietary fibre in laying hens: a review of effects on performance, gut health and feather pecking. World’s Poultry Science Journal, 77:4, 797-823. (Link to the article)
Lázaro, R., M. Garcia, M. J. Aranibar, and G. G. Mateos. 2003. Effect of enzyme addition to wheat-, barley-and rye-based diets on nutrient digestibility and performance of laying hens. British Poultry Science 44 (2): 256–265. (Link to the article)
Mirzaie, S., M. Zaghari, S. Aminzadeh, M. Shivazad, and G. G. Mateos. 2012. Effects of wheat inclusion and xylanase supplementation of the diet on productive performance, nutrient retention, and endogenous intestinal enzyme activity of laying hens. Poultry Science. 91 (2): 413–425.
(Link to the article)
Röhe, I. and J. Zentek. 2021. Lignocellulose as an insoluble fiber source in poultry nutrition: a review. Journal of Animal Science and Biotechnology. 12:82. (Link to the article)
Tejeda, O. J. and W. K. Kim. 2020. The effects of cellulose and soybean hulls as sources of dietary fiber on the growth performance, organ growth, gut histomorphology, and nutrient digestibility of broiler chickens. Poultry Science. 99 (12): 6828–6836. (Link to the article)
One Response
Very informative content. Thanks.