Anti Nutritional Factors(ANFs) in Feeds & Fodders: Method & Control measure to reduce deleterious effect
Dr.CK Sant,Dairy Advisor,Pune
Harmful natural constituents are also called as anti nutritional factors.
Anti-nutritive substance is defined as “those generated in natural feedstuffs by the normal metabolism of the species and exerts effects contrary to optimum nutrition”.
It is well known that nutrition is one of the main factors driving the functioning efficacy, efficiency and evolution of livestock system. The main challenges nowadays in ruminant production are to reduce feeding cost, improve products quality and diminish the impact of production on environment. The use of unconventional feedstuffs may contribute to decrease feeding cost and environmental impact through reduced methane emissions as well. Not only that, but shrubby plants can be used to combat desertification, mitigating the effect of drought, allowing soil fixation an enhancing the restoration of the vegetation and the rehabilitation of rangelands. In the meantime, browsing tree foliage plays an important role in ruminant feeding systems in many tropical and Mediterranean environments around the world. They are chiefly as good, cheap sources of nitrogen and energy, which may reduce feeding cost and raise small ruminants productivity in arid and semi-arid zone. So, to reach that goal, it must exploit all that is available either unconventional feedstuffs or browse and shrubs. However, the problems of feeding such plants or shrubs (Acacia, Leucaena and Atriplex) that they had different levels of anti-nutritional factors.
Anti-nutritional factors
Anti-nutritional factors (ANFs) are substances that when present in animal feed or water they either by themselves or through their metabolic products reduce the availability of one or more nutrients. Plants contain starch polysaccharides and no-starch polysaccharides (NSPs), and some of them are anti-nutritional factors. NSPs contain sugars other than glucose and/or have linkages other then the linkages common in sugar. An example of an NSP is cellulose, that is a chain of glucose molecules, but the molecules have ß-(1→4) bonds between them. The different orientation of the ß-bonds (compared to α-bonds) makes them resistant to digestion by endogenous digestive enzymes of animals. Cell walls in plants contain cellulose and other polysaccharides or non-carbohydrate materials such as protein and lignin. Plants contain a mixture of both water-soluble and insoluble NSPs; and the ratio changes with type and stage of maturity of the plant. Cellulose is insoluble in water and is considered fiber. Most NSPs adversely affect digestion in animals, as they affect the viscosity of the material in the digestive tract, and in turn, affects the ability of the digestive enzymes to do their effect, in the end they results in reduced feed efficiency. Meantime, the utility of leaves, pods and edible twigs of shrubs and trees is limited as animal feed by the presence of ANFs.
The anti-nutritional factors may be classified on the basis of their effects on the nutritional value of feedstuffs, and on the biological response to them in the animal. Huisman & Tolman divided the anti-nutritional factors into groups:
Factors with a depressive effect on protein digestion and on the utilization of protein, such as protease inhibitors, tannins and saponins;
Factors that affect mineral utilization, which include phytates;
Factors that stimulate the immune system and may cause a damaging hypersensitivity reaction, such as antigenic proteins;
Factors with a negative effect on the digestion of carbohydrates, such as amylase inhibitors, phenolic compound and flatulence factors.
Also, it can present as:
Non-protein Amino Acids (Mimosine) as in Leucaena,
Glycosides (Saponins) as in Acacia
Polyphenolic compounds (Tannins, Lignins) as in all vascular plants
Alkoaois as in Acacia and Oxalate as in Acacia as well.
The mechanism of action of mimosine is not clear, but it may act as an amino acid or make a disruption of the catalytic, trans-aminases, or may complex with metal such as Zinc.
To come over to the minomsine problem when feeding Leucaena, is to restrict to 30% of the green forage with cattle and buffalo, and 50% for goats.
Saponins are a heterogenous group of naturally occurring foam producing steroidal glycosides that occur in a wide range of plants, including oilseeds such as kidney bean, lentil, pea, chickpea, alfalfa, soybean, groundnut and sunflower.
They reduce the uptake of certain nutrients including glucose and cholesterol in the gut through intralumenal physicochemical interaction. Hence, they have been reported to have hypocholesterolemic effects.
Meantime, they have distinctive foaming characteristics with white clover and alfalfa; they can cause bloat, hemolysis and inhibit microbial fermentation and synthesis in rumen.
However, it has varied biological effects due to structural differences in their sapogenin fractions.
Tannins, are water soluble phenolic compounds, they are the most common type found in forage legumes, trees and shrubs.
They have the ability to precipitate proteins from aqueous solution. Tree and shrub leaves contain the two different groups (hydrolysable & condensed Tannins (CT)). Tannins have more effect in reducing digestibility than hydrolysable tannins. However, the mechanism effect of tannins came from their ability to form strong H bonds with nutrients resulted in inhibitions of digestive enzymes and rumen microbial activity, and their effect can increased with the increase of the tannins molecular significantly. Concentrations of 2-4% of DM increase N utilization due to increased bypass, Concentrations >7% usually reduce nutrient utilization.
Tannins are present in the NDF and ADF of the tree leaves, which are bound to the cell wall & cell protein and can resulted in decreasing digestibility, they also cause decreased palatability, feed intake, reduced growth rate or loss in weight, poor utilization and decrease iron absorption. But, on the other hand, tannins have some advantages due to their efficiency on animal health, as it had other properties such as, anti diarrhea, anti bacterial, anti oxidant, free-radical, scavenging ant proliferative activity in liver cells. Not only that but it can work as protein protection during ensilage.
Alkaloids cause gastrointestinal and neurological disorders. The glycoalkaloids, solanine and chaconine present in potato and Solanum spp. are toxic to fungi and humans. Some plant alkaloids are reported to cause infertility.Anti vitamin factors there are some anti-vitamin factors in some plants, especially leguminous plants. Anti-vitamin E has also been noted in isolated soya protein, which is suspected to be tocopherol oxidase. Anti-metals Phytates bind minerals like calcium, iron, magnesium and zinc and make them unavailable. Anemia and other mineral deficiency disorders are common in regions where the diet is primarily a vegetarian.
Oxalate is considered an anti-nutrient because it inhibits calcium absorption and can increase the risk of developing kidney stones.
Methods of reduce the deleterious effect of ANF’s
A number of methods have been tried to overcome the deleterious effect of such anti-nutritional factors and tannins is came at the head. These are through making hay, silage with inoculants, using PEG; urea or biological treatment with fungi can be applied to either take off or minimized and decrease anti-nutritional factors concentration.
It is will know that alkali treatment includes polyethylene glycol (PEG), which a tannins-binding agent, was shown to be a powerful tool for isolating the effect of tannins on various digestive function. But it may not be economic. Although the incorporation of polyethylene glycol (PEG), which binds with and inactivates tannins, is quite effective, success of its adoption depends on the cost: benefit ratio. Russsell & Olley suggest feed animals with 1% urea. In that system, urea not only provides extra N but also deactivates the leaf tannins.
Type of Anti-nutritive substances
On the basis of the type of nutrient affected and the biological response produced in the animal, the toxic factors can be classified into six major groups as follows:
Substances depressing digestion or metabolic utilization of protein:
Protease inhibitors
Lectins or Ricin (hemagglutinins)
Saponins
Polyphenolic compounds (Tannins)
Substances reducing the solubility or interfering with the utilization of mineral elements:
Phytic acid
Oxalic acid
Glucosinolates
Gossypol
Substances inactivating or increasing the requirements of certain vitamins and certain mineral:
Antivitamins A, D, E, K and anti-pyridoxine
Antiminerals such as Phytic acid, Oxalic acid etc.,
Mimosine (Anti hormone)
Nitrates and nitrites
Moulds and mycotoxins in animal feedstuffs
Identify anti-nutritional factors in animal feed:
Anti-nutritional factors (ANFs), also referred to as antinutrients, antinutritive factors, secondary substances or plant secondary metabolites, are constituents which may be used either by themselves or through their metabolic products. They interfere with animal feed utilisation and affect the health and production of animals.
Anti-nutritional factors may produce several adverse effects: reduce nutrient intake, digestibility, nutrient absorption etc.. Low level of anti-nutritional factors in any animal feeds are recommended and high levels of this factors are forbidden.
Identified problems:
The main challenges in animal production, especially for ruminants, are: reduce feed costs, improve products quality and increase production. In order to achieve this, farmers are encouraged to exploit the use of unconventional feedstuff, browse foliages and shrubs. However the problem of feeding such materials is the fact that they contain different anti-nutritional factors with different concentrations that cause detrimental effects to animals.
Why do plants feedstuffs contain anti-nutritional factors?
Anti-nutritional factors serves as defense mechanisms in plants.
Plants also produce and use antinutritional factors for plant to plant interaction, to fight their enemies and to interact with the external environment.
Plants produce and use antinutrients as natural pesticides:
to protect themselves against moulds, bacteria’s, birds and other insects that plays on them. Just to cite some examples: bitter taste, unattractive colours, poisonous, bad odor and immune suppressants.
Detrimental and beneficial effects of Antinutrients:
Anti-nutritional factors can cause unpredictable effects on animals when used in animal feed. Such effects can either be POSITIVE:
reduce parasite burden
reduce protein degradation in the rumen
reduce methane emission
reduce bloating in animals
or NEGATIVE:
reduce feed intake,
lower feed conversion
bind to protein and other important nutrients needed by animals in the feed
can also cause death in some cases.
Depending on the level of concentration of antinutrients in a particular animal feed. They interfere with the use of dietary nutrients in different ways, including:
Reducing nutrient digestibility by binding them.
Damage the animal digestive tract.
Reduce the digestive efficiency.
Can cause depression in animal growth and feed efficiency.
Affect animal health and performance.
Most common anti-nutritional factors in plant feedstuffs
The following deleterious Anti-nutritional factors are often tested through laboratory analysis of animal feedstuffs and forages used in feeding livestock. However the list can be endless depending on the interest of individual as feed safety is concerned in many countries.
The common antinutritional factors in animal feedstuff and forages are:
Saponins
Tannins
Protease inhibitors
Alkaloids
Non protein amino acids (mimosine)
Lectins (phytohaemagglutinins)
Trypsin inhibitors
Phytic acid
Oxalates
Amylase inhibitors
Cyanogenic glycosides
Aflatoxins and Gossypol.
Methods to counteract and reduce anti-nutritional factors in animal feed.
Applying appropriate techniques or effective processes or combinations of techniques could help to reduce or eliminate adverse effects of Anti-nutritional factors in animal feed. Common and cheap techniques aimed at counteracting or reducing Anti-nutritional factors in feedstuff include: the use of polythene glycol (PEG), drying of feedstuff, the use of wood ash, solid state fermentation technique and the use of activated charcoal (Biochar), etc. However every technique has its own consequences or implications such as cost, labour and effects on important nutrients in the feed needed by animals in the feed.
A better understanding and management of Anti-nutritional factors in animal feed is necessary to let farmers be able to apply more appropriate techniques to reduce antinutrients deleterious effects while enhancing their benefits and hence enabling the use of vast reservoirs of animal feedstuff.
Processing of Feed Stuffs
Various processing methods are being used to increase the voluntary intake, availability of nutrients and Nutritive value of feeds and fodders.
Grinding or Crushing – Cereal grains and certain seeds are grind or crushed to smaller particle size. It increases the surface area for action of digestive enzymes as hard seed coat is broken, thereby increasing the digestibility. Coarse grinding is preferred for grains and seeds.
Chaffing – It is Process of cutting roughages especially fodder crops into smaller size pieces. It minimizes the fodder wastage.
Soaking – Soaking of feeds and fodders in water removes dustiness and softens the coarse feed material. Soaking of straw removes some oxalates. It improves nutritive value of feed stuffs.
Heat treatment – It is applied especially in the production of oil seed cakes. It helps to reduce most of the antinutritional factors present in oil cakes.
Pelleting – Coarsely grinded concentrate feed is mixed with binder substances like sodium bentonite and made into small cylindrical cubes called as pellets. Pelleting of concentrate mixture ensures the intake of all components of feed.
Alkali Treatment – Cereal straw have very poor nutritive value due to presence of poorly digestible components like cellulose, hemi cellulose and lignin in higher proportion. Alkali treatment with 3.3 percent NaOH
@ 1 litre/kg of chaffed straw or 5.5 percent CaOH at 40-60 percent moisture. It improves the voluntary intake and digestibility of straw.
Urea treatment – The poor quality roughages like straw or mature grasses are treated with 1-3 percent urea and moisture level is kept at 50 percent level, which is then stacked for 20-30 days till residual ammonia is removed. The urea treatment breaks the lignocelluloses complex and also adds nitrogen to fodder thereby increases its protein value.
Formaldehyde or Tannic acid treatment – This protects the feed protein from microbial action in rumen and directly reaches to small intestine.
Formaldehyde or tannic acid treatment is given to protein rich concentrates like oil seed cakes. The oil seed cakes are made into powder and mixed with formaldehyde @ 5ml/100gm of crude protein of oil cake or 3 percent tannic acid. It is then stored for about 2 weeks in closed container.
Reference-On Request.
