In our previous article, we discussed the digestion kinetics of various fiber types, the effects of fiber on nutrient utilization, gut microflora, and immunity. This article discusses the effects of dietary fiber on laying hens’ performance, stress, and feather pecking.
Effects of dietary fiber on stress
The welfare aspect of nutritional programs can be assessed through physiological indices of stress such as elevated blood heterophil:lymphocyte ratio, corticosterone levels in plasma, cecal content, colon content, feathers, and behavioral changes such as stereotypic object pecking, over-drinking, and hyperactivity. Stress compromises gut health affecting gut integrity, permeability, and the immune system. Feeding appropriate types and levels of fiber can minimize the stress effects, supporting gut health. Feeding fermentable non-starch polysaccharides (NSP), especially fermentable oligosaccharides, has alleviated stress levels in chicken. The reduction in stress level was confirmed by reduction in the counts of heterophils in the blood as a physiological index of stress.
Effect of fiber on laying hen performance
Pelleted alfalfa was used in a study at different levels as a fiber source on Lohman Brown hybrid pullets from 9 to 16 weeks of age (Panaite et al., 2016). The results showed that using 8% pelleted alfalfa in the diet significantly increased pullet body weight by 6.73% higher than the Lohman Brown management guide. This might be because of the improvement in gizzard development as a result of using fiber in the diet. In another study, using lignocellulose at 1 kg per ton of feed increased body weight, feed intake, egg production, eggshell quality, egg yolk index percentage, and feed efficiency compared to the control group (Sozcu and Ipek, 2020).
Kocer et al. (2021) investigated the effects of supplementing laying hen diets with 3%, 4%, or 5% fiber using high-fiber sunflower meal from 21 weeks of age onward. They reported that by increasing the dietary fiber, body weight, egg production rate, and eggshell quality were increased, and the percentage of shell-less eggs and cracked eggs were reduced. Eggshell quality improved because providing fermentable fiber in laying hens diet can decrease intestinal pH and improve solubility and absorption of calcium and other minerals.
Effects of fiber on feather pecking and cannibalism
Abnormal behaviors such as feather pecking, and cannibalism can cause serious welfare, health, and financial damage to the egg industry. Insoluble fiber and coarse fiber ingredients can increase the eating time and reduce feather pecking and cannibalism in poultry. It has been shown that fiber source matters when it comes to such abnormal behavior. For instance, oat and barley are more beneficial than wheat in reducing cannibalistic behavior (Abrahamsson et al., 1996; Wahlstrom et al., 1998). Feed form also plays an essential role in fibrous diets. High-fiber diets were more effective in reducing feather pecking when the feed was provided in mash form compared to the pellet form. This might be because birds have to spend more time ingesting mash diets, satisfying their grazing behavior.
Changing the fate of fiber in the gut
As discussed in our previous article, soluble NSP can compromise poultry digesta viscosity and gut function if not appropriately managed. It is recommended to use targeted fiber components (various isolated forms of fiber), proper processing techniques, and exogenous enzymes in the feed to overcome these challenges. Feed processing and enzyme supplementation can change the fate of the dietary fiber in the gut, increasing fiber digestibility and other nutrients to produce fermentable resources for the gut microbiome. These fermentable resources serve as prebiotics, enhancing the population of beneficial bacteria. This subsequently improves the immune system and gut health.
Effects of NSP-degrading enzyme supplementation on fibrous diets
In one of our previous articles, it was mentioned that the poultry industry in different countries is moving away from using Antibiotic Growth Promoters (AGP) by replacing them with some potential alternatives. In the absence of AGP, more attention should be paid to feeding the beneficial gut microbiota; this can be done by providing a substrate for the microbiota using NSP-degrading enzymes and prebiotics. The NSP-degrading enzymes can provide fermentable oligosaccharides as a substrate for the beneficial bacteria (prebiotic effect), degrading the soluble and/or insoluble NSP.
To get the most benefit out of NSP-degrading enzymes, some multienzymes have been designed as a “cocktail enzyme”, which contain several NSP degrading enzymes such as xylanase, amylase, glucanase, cellulase, mannase, and pectinase. Cocktail enzymes break down plant cell-wall matrix, particularly the insoluble components. These enzymes subsequently can release encapsulated nutrients, increasing the accessibility of digestive enzymes and nutrient absorption. Otherwise, unabsorbed nutrients (sugars) in the gut can cause osmosis of water into the gut lumen, increasing water excretion through excreta.
The main NSP-degrading enzyme is xylanase. In all NSP-degrading enzymes, xylanase is used either alone or in combination with other carbohydrase enzymes. The latter form, as mentioned, is a cocktail form. Xylanase degrades the internal glycosidic linkages in xylan and arabinoxylan and turns them into short-chain XOS (Xylan oligosaccharides) and AXOS (Arabinoxylan oligosaccharides), respectively. Intestinal bacteria ferment the latter products to produce short-chain fatty acids (SCFA), which are used as an energy source for the bird.
The efficacy of NSP-degrading enzymes depends on bird age, NSP type (grain type), the dose of NSP-degrading enzyme, and the effects of other enzymes in multienzyme products. The type of microbiota can affect the utilization of NSP. NSP-degrading enzymes help establish NSP-degrading bacteria in the gut; the better utilization of NSP, the fewer issues related to digesta viscosity, water consumption, and retention. NSP-degrading enzymes are more effective during early life when the microbiome has not been established completely. If xylanase is fed in the starter phase, more xylan-degrading bacteria will be established in the microbiota of young chicks, enabling them to utilize dietary NSP in the subsequent phases.
Processing the dietary fiber
Feed processing techniques such as chemical, enzymatic, irradiation, milling, pelleting, etc., can affect fiber behavior in the gut, reducing adverse effects and increasing the most beneficial effects of fiber. Processing fibrous feed by hammer and roller milling increases the solubility and digestibility of NSP fraction. Adding NSP degrading enzymes to ingredients subjected to hydrothermal processing increases fiber digestibility by 1.5 to 6 times. Pelleting and micronizing can promote pentosanase action (a 5-carbon carbohydrate degrading enzyme) on fiber.
Enhanced lignocellulose (OptiCell or eubiotic lignocellulose) is a processed form of fiber that contains fermentable fiber. This product can reach its potential, exerting beneficial effects of fiber at as low as 0.5 to 1% of the diet without diluting dietary energy. This low dietary inclusion rate will guarantee the benefits of fiber without compromising dietary energy levels and feed intake.
In conclusion, animal nutritionists can change fiber “threats” to healthy flock opportunities using proper nutritional strategies. Fiber can then be used as a stress-reducing, immune-boosting, and performance-enhancing feed component in laying hens diets. Further research is warranted to define what type and levels of fiber can be used to reveal the potential benefits of this mysterious feed component.
References
Abrahamsson, P., R. Tauson, K. Elwinger. 1996. Effects on production, health and egg quality of
varying proportions of wheat and barley in diets for two hybrids of laying hens kept in
different housing systems. Acta Agriculturae Scandinavica, Section A – Animal Science 46(3):
173–182. (Link to the article)
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)
Kocer, B., M. Bozkurt, G. Ege, A. E. Tuzun. 2021. Effects of sunflower meal supplementation in
the diet on productive performance, egg quality and gastrointestinal tract traits of laying
hens. British Poultry Science. 62(1): 101–109. (Link to the article)
Sozcu, A., and A. Ipek. 2020. The effects of lignocellulose supplementation on laying
performance, egg quality parameters, aerobic bacterial load of eggshell, serum biochemical
parameters, and jejunal histomorphological traits of laying hens. Poultry Science. 99 (6):
3179–3187. (Link to the article)
Wahlström, A., R. Tauson, and K. Elwinger. 1998. Effects on plumage condition, health and
mortality of dietary oats/wheat ratios to three hybrids of laying hens different housing
system. Acta Agriculturae Scandinavica 48: 250–259. (Link to the article)
