Mycotoxins binders- How to get the best value for money
Dr. S. Subramanya Bhat, Product Manager - Poultry,
The poultry industry has seen a tremendous growth with the best application of nutritional technologies. Today the feed production has been paid a good deal of attention. However feed safety is a concern for achieving productivity. Mycotoxin contamination of feed is recurring problem. However the effective control is a challenge because the mycotoxins contamination occurs through various raw materials, which are used in poultry feed. Nevertheless the contamination of mycotoxins can come from the dust and leftover feed in the feeding channel. Hence a rational approach has to be adopted for effective control of feed mycotoxins.
Mycotoxins are secondary metabolites produced by certain toxigenic fungi in the poultry feed and ingredients. The feed/ ingredient contamination with toxins may occur anywhere in the supply chain, starting from the harvest of maize or oil pulses, to storage to feeding channels in the farm. These mycotoxins when gets into the system may cause moderate to severe toxicity symptoms. They include digestive disturbances, feed refusal, and lower feed intake, liver damage, nephritis, immunosuppression and poor productivity. In severe cases toxicity may result in high mortality rate (Fig 1). Low levels of prolonged ingestion of mycotoxins can be more hazardous than what it was thought about. The concern is also about the toxin-toxin interaction.Aflatoxicosis
The effects of aflatoxins on health and productivity of poultry varies with concentration of intake, length of exposure, species, breed, diet and nutritional status. Furthermore, research showed that young chicks are more sensitive than adults. The damage to birds can be grouped into four stages:
Toxin- Toxin Interaction:
Ochratoxin A: It is produced by A. parasiticus or Penicillium ochraceus. These molds grow under conditions normally favourable for Aflatoxin mold. Ochratoxin is a potent nephrotoxin and at low levels over a period can be immunosuppressive. When present along with aflatoxin the toxicity will generally be exaggerated.
Citrinin: It is produced by A. oryzae. These molds commonly contaminate maize and cereals, under high humid climatic conditions. The clinical symptoms are because of cumulative toxicity. Normally it will result in increased water consumptions.
The best method adopted till date to control the mycotoxins in poultry feed is the use of toxin binders in the feed. They are clayey soil of specific nature, which has the capacity to bind mycotoxins in the GI tract, avoid their absorption and ensure their elimination.
Clay soils (HSCAS) are available in plenty. The fact is that not all HSCAS will have an assured binding efficacy to mycotoxins. Their binding property is depending upon a variety of physical and chemical properties of the clay. Hence the entire process needs a careful selection of clay, which can give the desired results.For an effective mycotoxin removal strategy, the nutritionist and the feed mill shall look into a more detailed approach. The selection of a feed additive for the control strategy shall give an effective control and best return for value. While selecting a toxin binder one need to pay attention to the following criteria:
Binding efficacy: This is an estimation of the binding activity of the additive to different mycotoxins. Different physical and chemical properties of the additive will influence the binding efficacy. Only a careful selection of the clay, minimum impurities, desirable pore size and ionic characters will yield good binding efficacy. Again different mycotoxins have varying affinity for different clays. The mycotoxins have predominantly negative charges as in aflatoxin, or mixed charges as in other mycotoxins. The selection of clay shall match this charge distribution in an opposite way. This will enable the binder to bind mycotoxins and avoid its absorption. The pore size in the clay shall be moderate to fit mycotoxins molecule. If it is excess, there is every possibility that it will absorb water and along with that vital nutrients.
Binding efficacy is expressed as % binding of a mycotoxin, either in a single toxin environment or in a multitoxin environment.
Binding stability: The binding of mycotoxin takes place in gizzard, at an acidic pH. It doesn’t happen in the feed outside the body. Hence this requires certain activation time, after the feed is consumed by the bird. If the activation time is too long, the feed may pass through the gizzard, without toxin binder interaction.
Secondly, once the mycotoxins are bound by additive in the gizzard, the chyme passes through the intestine. There the toxin-binder complex is subject to a more neutral or slightly alkaline environment. If a careful selection is not made about a binder, at this place, the bound toxins may be released and the bird absorbs toxins (Fig 3).
To avoid this, a detailed study approach about the binder selection and quality assurance is a mandatory.
A stable binding is that the binder binds mycotoxins in the gizzard, but will not release them even at neutral or alkaline pH, ensuring that the complex passes through the intestine and ensure safety to birds.
Effective inclusion rate: For the safety of the entire feed the toxin binder shall be distributed evenly in the feed. The binder doesn’t have an attraction property; rather the vicinity of the toxins to binder during churning in the gizzard is a determining factor for effective binding. This has to be achieved with a proper surfactant.
Least active on nutrients: Nutrients differ in their molecular size from that of mycotoxins. The selection of the binder based on a porosity which is suitable for mycotoxins, eventually excludes nutrients is an ideal binder. These additives are ideally called toxisorbents (specific to mycotoxins) and needs to be differentiated from enterosorbents, which behave indifferently to mycotoxins and vital nutrients. Some HSCAS will have a hydration property owing to their very large surface area; thereby they swell in the intestine. Such clays are clearly not a suitable binder as they bind nutrients along with mycotoxins.
These parameters need to be tested extensively in the R & D, during the development of binder. More importantly, these procedures must be made part of the regular quality assurance protocol of the manufacturing facility for toxisorbent.
These factors should be considered while selecting a good toxisorbent for inclusion in the feed. A good toxin binder should be complementary to other mycotoxin control strategies, like good sourcing of raw materials, good storage practice and feed mill hygiene. This will make the strategy “value for money”.