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Fiber as an essential poultry nutrient – turning a problem into a solution

Fiber is an essential nutrient for poultry. Research shows the inclusion of high-fiber ingredients can improve broiler performance, health and welfare.

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The difficulty of using high fiber raw materials — and ways to improve their nutrient availability – is always a hot topic. However, fiber is functionally important for poultry performance, health and welfare. While some fiber is indigestible, it performs vital actions within the gastrointestinal tract. For example, it modulates both gizzard function and digesta passage rate. In the case of laying hens, providing enough fiber has been shown to reduce feather pecking and other vices. 

This article will focus on the benefits of insoluble structural fibers and discuss its role in improving the health and welfare of all classes of poultry.

Types of fiber

Fiber is generally described as either soluble or insoluble. The crude fiber values given for ingredients refer to the insoluble fraction. Insoluble fibers include the non-starch polysaccarhides (NSPs) cellulose and hemi-cellulose, as well as lignin. The proportions of these in a raw material will affect its digestibility. Crude fiber is indigestible by the birds themselves but can be a food source for bacteria. These fermentable fibers are turned into short chain fatty acids, providing energy. This prebiotic effect, favors beneficial bacteria, resulting in improved intestinal health.

Soluble fibers can be absorbed by birds and include the NSPs xylan and beta-glucan. These are associated with increased gut viscosity, which lead to sticky droppings and reduced nutrient availability. Processing and the addition of enzymes help to alleviate these negative effects. Cereals contain both kinds of fiber, but cereal by-products and sunflower seed meal contain higher levels of insoluble fiber. 

The role of fiber in the gut

When formulating rations for poultry, the role of the gizzard cannot be ignored. Its muscular structure grinds the feed, increasing surface area to improve digestibility. It is the pace maker of the digestive system, controlling acid secretion. Insoluble fiber helps develop the gizzard, in turn improving its efficiency. It also increases the size of the organ, meaning that feed is held there for longer, lowering pH and reducing pathogen load.

It has been demonstrated that hens kept in cages have lower gizzard weights than those in contact with litter. This is because if diets don’t contain sufficient insoluble fiber, birds will consume litter or even feathers to compensate. Through its Nutrition Innovation Center, Dutch ag cooperative ForFamers has developed a unique way to score the gizzard by assessing the passage between the proventriculus and the gizzard, which includes the overall development of the gizzard wall. 

Higher dietary fiber levels reduce the rate of passage of digesta. It should be slow enough to allow good digestion of nutrients without allowing proliferation of pathogens. Fiber also improves gut wall integrity, digestion and immunity. This in turn has a positive influence on production parameters such as litter quality, food pad score, breast blisters and dirty eggs.

The effect of fiber on performance

Responses to increased fiber levels depend on the class of poultry. 

In a recent trial, researchers compared the effect of dietary fiber level on the performance of broiler and layer chicks up to 21 days of age. Feeding a high-fiber diet significantly reduced the average daily gain (ADG) of broilers, but had no effect on layers. 

This effect is thought to be due to the function of growth rate. Broilers grow faster, eat more and are therefore less able to cope with fiber. Being slower growing with smaller appetites, layers can handle higher levels. Improved fiber digestibility was also observed in the layers; however, there was no significant effect of feed efficiency in either group. There is also an age effect on response to fiber due to level of gut development and capacity.

Benefits to welfare of poultry

Many factors affect the incidence of vices such as feather pecking in laying hens, but increasing dietary fiber level has been shown to reduce it. By diluting the diet with fiber rich ingredients, birds spend longer eating, which reduces the time available for these injurious behaviours. Increasing feed volume also improves satiety, particularly as fiber swells with the addition of water. 

Increasing fiber levels commercially is seen to improve feather cover and plumage quality.

The reasons for this are thought to be that hens consuming sufficient fiber are more content. Therefore, they are not searching out roughage, which they may choose to get from feathers. The effect of fiber on digestive health is also though to reduce stress, thereby reducing unfavorable behavior. 

Feed restriction of broiler breeders can also result in vices. Providing a less nutrient-dense, high-fiber diet has been shown to alleviate this and can improve performance. 

The economics of high-fiber diets

If dietary fiber levels can be increased it gives nutritionists the option of including more high fiber ingredients. This may have a positive effect on sustainability, e.g. making use of canola over soybean meal. Depending on availability, this could also reduce the cost of rations. 

Certainly inclusion of a wider variety of raw materials is possible. In Western Europe, for example, more barley and oats are included in poultry diets. Sunflower is a popular choice for laying hen diets as it supplies energy and protein along with insoluble fiber. Cereal byproducts also offer higher levels of fiber and their inclusion can increase the fiber content of diets by 3 to 5 percent, compared with a corn and soybean diet. 

The practice of whole wheat feeding in turkeys is another example of increasing fiber levels to both reduce feed costs and improve digestive health. When formulating layers mash in many countries there is no need to set a minimum as the ingredients used provide sufficient levels. However, if fiber levels are above 10 percent, feed intakes won’t meet requirements. 

For breeders, there is a limit to how much a diet can be diluted whilst still forming a pellet. In broilers there is a move to increase fiber levels and grist size within pellets. The focus is on including materials such as oat husks, which contain fiber that holds its structure even after grinding. It is this kind of coarse, durable fiber, which stimulates the gizzard. After three weeks of age, inclusions of 5 to 8 percent for breeders and 2 to 3 percent in broilers, has been recommended.

Fiber has its benefits

Whilst the benefits of fiber are more widely recognized, minimum fiber levels are hard to come by; although nutritionists will have their own rules of thumb.  However, the effect of fiber on preventing vices in laying hens is generally accepted.

It has been shown that birds have an innate requirement for roughage and will seek out fibrous material to satisfy this need. Therefore, more attention needs to be paid to fiber requirements in order to improve poultry health, welfare and performance. Research should focus on the effect of level, source and type of fiber in different classes of poultry. However, there is a limit to how much fiber will “fit” into a high-energy broiler ration. 

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