In the recent past Fibre was not so much important particularly in commercial layer diet, though it was a part of feed formulation depending on the raw materials used around the world. The most common raw materials used in layer diets are corn and soya, but other grains like different brans, MDOC, SFDOC etc are also being used in different countries depending on availability. In recent times new scientific work shows that fibre and structured materials have a lot of benefits in layers’ diets and should be used as a tool to improve nutrition of layer breeds under varying circumstances and under probably varying raw material availability.
Digestible Fibre (DF) is generally defined as the non-digestible fraction of plant cell walls in food and feed ingredients and typically includes oligosaccharides, pectin polysaccharides, hemicellulose, cellulose, lignin, gums, and some minor associated plant cell wall substances. Vegetable roots and fruits like apple, beetroot, oranges provide mainly soluble fibre which is pectin whereas all kinds of cereal brans like rice bran, rice polish, wheat bran etc provide higher amount of insoluble fibre which is cellulose. In order to more accurately predict the nutritive effect of fiber from raw materials, a better characterization of fiber fractions, their degradation in the chicken, and their physiological effects are required. Traditional analytical methods to analyze fiber, as crude fiber (CF) and neutral detergent fiber (NDF), recover only a variable part of the fiber fraction and are hence unfit to evaluate fiber fractions in raw materials and poultry diets. In the chicken, solubilization is a prerequisite for fermentation, but even if solubilized during the digestive processes, a substantial part of non-starch polysaccharides (NSP) may remain undegraded.
There is some evidence that insoluble fibres have a positive effect on selected parameters in poultry production. Thus, digestibility of starch is higher and digesta passage rate faster when a moderate level of insoluble fibre is present in the diet. Due to the faster passage rate there is less accumulation of toxic substances in the intestinal tract. The effect of insoluble fibre on gut function stems from its ability to accumulate in the gizzard, which seems to regulate digesta passage rate and nutrient digestion in the intestine.
Fibre in layer diet:
Now a days many breeding companies are emphasizing in their feeding guidelines importance of fibre in layer diets. Insoluble NSP used in the later part of the rearing period can positively influence the development of the digestive tract, the crop size and the appetite of the pullets. This is the reason why breeding companies implements a minimum recommendation of crude fibre (5-6%) in the developer feed. During the second half of the rearing period it is highly recommended to increase crude fibre in the developer feed with the aim to create a good and sufficient feed intake capacity for a pullet which is able to start with sufficient daily feed intake and high performance after transfer to the layer house and to show up the real genetic potential. Although high density diets can be used to improve body weight gain, the sustained feeding of diets with higher than recommended energy contents or with a low fibre content can result in inadequate development of the birds’ capacity for feed consumption leading to low feed intake and low egg production during early lay. According to Lohmann Tierzucht, cereals and their byproducts (bran) or oil seed byproducts (meal of sunflowers) can be used as a source of crude fibre. They point out that the recommended crude fibre content is difficult to achieve with a classical corn-soya formulation. In such cases crude fibre products based on lignocellulose are an option, as they are high in fibre (50- 65%), free of mycotoxins and do not consume too much space.
Cannibalism and Fibre in Layer diet:
Mortality caused by cannibalism continues to be a major problem in the layer industry. Up to 20% mortality from cannibalism has been noted insome strains, depending on the production system and management strategies. Beside the management, the genetics and the lighting program, dietary factors likelow protein diets, low sodium intake as well as a lack of some essential amino acids are seen asthe causes of cannibalism. More and more trials also show the importance of an adequate level of insolublefibre in the formulations to prevent cannibalism.Insoluble fibre has a positive impact on performances in terms of laying percentage as well as on animal welfare. Soluble fibre on the other hand depress the digestibility of protein, starch and fat due to their negative impact on digesta viscosity.Layer farmers all around the world know the problem that sometimes layer flocks in non-cage housing systems tend to eat litter and feathers. With regard to the new knowledge and experience in terms of crude fibre the question may come up if litter and especially feathers are taken up as sources of structure and fibre. If those flocks have access to roughage and other sources of coarse crude fibre, eating of feathers and litter will decrease.A trial at the University of Hohenheim established that strains with high incidence of feather pecking ingest more feathers than strains with low incidence of feather pecking. Moreover, the authors discovered that feathers have the same effect in the intestinal tract as insoluble fibre, which is the acceleration of the intestinal transit period. A logical conclusion is that the animals ingest the feathers to overcome a deficiency of insoluble fibre.
Fibre and Gut health:
Crude fibre has no obvious nutritional value and all raw materials with increased content of crude fibre have less energy compared to corn. Because of this traditional fibre sources do not calculate by linear programming into high energy poultry feed. In the literature some information about feeding trails can be found where scientists tried to evaluate the benefits of increased content of crude fibre in layer nutrition together with sometimes excessive energy dilution of the feed. In those trials the benefits of crude fibre could be confirmed but performance was compromised. This information has contributed to the bad reputation of fibre in layer diets even up to now. But most customers are facing the situation that the energy of the feed is a kind of fuel for nowadays modern layer birds. Due to this situation different kinds of fat and oil are standard raw materials nowadays as high dense energy raw materials and being an ideal solution to compensate the lower energy content of all the alternative raw materials compared to corn. countries like SCA where the alternative grains are being used together with added fat and oil it can be stated that ‘fibre and fat are feeding well´. Feed with added fat and oil with a certain content of crude fat is additionally a tool of feeding for liver health and to counteract the incidence of the so called ‘fatty liver syndrome´.
Fibre and Gizzard size:
For optimum feed intake during the onset of laying, gizzard size plays a very important role. This is important particularly during the heat stress period as well. One of the important roles of whole grains has been associated with their ability to stimulate the activities of the gizzard. This, in turn, is believed to be related to physical structures of whole grains. The major chemical component important to the structural integrity of grains is the insoluble fiber, which makes up the main part of the cell wall architecture. Indeed,insoluble fiber itself has shown beneficialeffects on nutrient digestion andgizzard activities. Recent research hasshown that digesta passing through the gizzardhave a remarkably consistent particle size distributionwith the majority of particles beingsmaller than 40 μm in size regardless of theoriginal feed structure. The fact that gizzard contents have higher fiber content than the feed illustrates that fiber is harder to grind than other nutrients and thus is accumulated in the gizzard . For layers on floor and in modified cages, litter can be a significant source of insoluble fiber.
In addition, recent studies indicate that structural components of the feed or litter ingesta may play a role in preventingcannibalism among layers. If so, such components as wood shavings may also be an important enrichment of housing systems.
If the gizzard size is inadequatethere will be a negative impact onperformance as well. The aim shouldbe, therefore, to make sure the gizzardat the end of the pullet stage isas big as possible. It is well established that particle size of feed has impact on the gizzard size.
Fibre and layer Performances:
In many university trials a positive impact of insoluble fibre on performance has been observed. The animals that received crude fibre in the formulation including some amount of crudefibre from the insoluble crude fibre showed increased hen day egg production (average production in the first 16 weeks) compared to the animals that received crude fibre only from traditionalfibre sources. This demonstrates that the nature of the fibre has a major impact on performance. In poultry, insoluble dietary fiber has shown beneficial effects on starch digestion. Insoluble fiber increased total bile acids in the gizzard. That insoluble fiber decreases the nutrient concentration may also play a role by increasingdigestive juices and substrate relationship. The current data and previous experiments show that the fiber level of the gizzard contents is about twice that of the feed. This means that fiber structures accumulate in the gizzard and that retentiontime of insoluble fiber is longer than for othernutrients. Fibers, such as cereal hulls, are verysolid and can probably be retained for a longtime in the gizzard. In contrast, whole cerealsthat mainly consist of starch granules and proteinwill be dissolved very fast in the acidic gastricfluid in the gizzard. Thus, the gizzard activityis more strongly stimulated by fiber structurescompared with whole cereal structures. The gizzard has been found to play a major role for gastroduodenal reflux of digesta. An empty gizzard will not have feed stimuli and as such will not be able to regulate downstream digestive processes.This, once again, supports the hypothesis thatbirds may have a requirement for fiber for stimulationof the anterior digestive tract and that afunctional gizzard needs contents with structuralcomponents.
Conclusions:
Crude fibre in layers’ feed may be a new and challenging topic for poultry nutritionists. an increased content of crude fibre in layers’ feed never will harm any bird. Increased content of crude fibre should never dilute the energy content of the feed. When these preconditions are emphasized, a lot of layer flocks will show positive effects getting a diet with higher content of insoluble crude fibre. A lot of raw materials instead of corn and soya can be used for layer feed, as practical experience is showing in several countries. The gizzard has an excellent ability to grind coarse components. Coarse particles are selectively retained in the gizzard until they are ground to a certain critical size. Structural components in the form of whole cereals and coarse water-insoluble fiber can improve feed use in birds fed highly concentrated diets. Formulations high in insoluble fibre result in better performance, a bigger gizzard, better intestinal health associated with drier litter, and in a reduced incidence of behavioural disorders like cannibalism. Lignocellulose products may be a good tool to use the benefits of insoluble crude fibre in layers’ feed.
References available on request:
by Dr. Koushik De, Director, Technical Services. SCA, Novus International
