A consortium of companies concerned with the sourcing and supply of bentonites to the feed industry (the European Bentonite Producers Association—EUBA aisbl) is seeking the re-authorization by the European Commission of bentonite as binders and anti-caking agents and authorization for a new application: the control of radionuclide contamination.
The European Food Safety Authority (EFSA) Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety, for target animals, consumer, users and the environment, and the efficacy of a group of bentonites. Bentonites are colloidal and plastic clay materials composed largely of montmorillonite (a species of dioctahedral smectite). The properties of bentonites can vary considerably depending on geological origin and any post-extraction modification, and their individual characteristics have a marked bearing on their economic use. Bentonites (E558) are currently authorised for use as feed additives, with the name “Bentonite-montmorillonite”, as binders, anti-caking agents and coagulants under the category technological additives to a maximum of 20 g/kg feedingstuffs. They are also authorised for use as food additives.
The results of studies submitted by the applicant showed that both chickens and piglets tolerate bentonite addition at 3 % of diet and dairy cows tolerate bentonite at 2 % of total intake. Although these studies were carried out using a single sample of bentonite, its composition was typical of most other bentonites described in this application, and so these results are considered to extend to other bentonites. Other data from the literature show that trout tolerate bentonite at 2.5 % of diet (the lowest concentration studied):
Eya et al. (2008) assessed the effects of bentonites on the performance and body composition of rainbow trout. During the feeding trial, quadruplicate groups of 15 rainbow trout (mean initial weight ± SD, 104.2 ± 0.7 g) were grown in freshwater (salinity, 0 %; temperature:, 14–16 16 °C) over 90 days. Fish were hand fed twice a day with diets containing 40 % crude protein supplemented with 0 %(control), 2.5 %, 5.0 % or 10 % bentonite. Alpha-cellulose replaced bentonite in the control diet in order to keep the diet isonitrogenous and isoenergetic. There was a statistically significant decrease (P < 0.05) in percentage weight gain, specific growth rate and feed efficiency in fish fed dietary bentonite at 5 % and 10 % compared with those fish on the control diet.
In poultry, 0.5 % bentonite reduces manganese availability in chickens for fattening. Given that any authorisation will be for bentonites limited only by specification and that the application is for all animal species, and as a margin of safety is difficult to establish, the FEEDAP Panel considered that the presently authorized limit of 2 % of diet (20 000 mg/kg complete feed) should be retained.
The data available suggest that addition of bentonites to diets is incompatible with the use of robenidine as a coccidiostat. Levels of bentonite higher than 0.5 % are also expected to reduce the effectiveness of other coccidiostats.
The FEEDAP Panel saw no reason to be concerned for the safety of consumers of food products derived from animals fed diets containing bentonite.
Bentonites added to feed contaminated by radioactive fallout or made available to grazing animals will reduce levels of radiocaesium in animals and their products. Since the use of bentonites for this purpose will be restricted to emergency situations, the FEEDAP Panel does not see a reason to set a maximum limit.
The Panel recommends that the definition of a bentonite for feed use should specify a minimum smectite content of 70 % and that restrictions should be placed on the concurrent use of bentonites with coccidiostats and some other medicinal substances.
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