3.4. Regulation of Probiotics used as Animal Feed
Additives
In contrast to the relatively undefined position of starter
cultures, and specially probiotics, in the EU legislative framework,
products intended for animal feed additives are closely
regulated. Animal feed additives have been regulated by the
Council Directive 70/524/EEC, while Council Directive
87/153/EEC defines the guidelines for the assessment of feed
additives. Council Directive 70/524/EEC has recently been
replaced by Regulation 1831/2003 EU. As noted above, the
relevant scientific committee (SCAN) has acted as an expert
body both in evaluating the feed additives and in formulating
the guidelines. In 2001, SCAN updated the instructions on
the efficacy and safety assessment of enzymes and microorganisms
used as additives in feed stuffs. SCAN has also
expressed opinions on the safety of Bacillus species in
animal nutrition (2000) and on criteria for assessing microorganisms
resistant to antibiotics (2001, revised in 2002).
The opinions regarding bacilli and antibiotic resistant microorganisms
reflect the special concerns caused by new
findings on the toxigenicity of certain Bacillus species and
the attention paid to the problem of increased prevalence of
antibiotic resistant bacteria in the food chain. The revised
guidelines of 2001 are intended to make a clear distinction
between chemical feed additives and enzymes and microorganisms,
and to streamline the test procedures accordingly.
Together, these guidelines and opinions define the only
existing European testing requirements for new microbial
strains and, therefore, deserve closer inspection.
3.4.1. The SCAN Guidelines on Safety Assessment of
Enzymes and Micro-Organisms
According to the 2001 guidelines, the safety of microorganisms
used as feed additives has to be established with
respect to the target animal, operator/user and to the
consumer. The safety has to be demonstrated using specific
tests and studies described in the guidelines. Strains
producing toxins (see 3.4.1.4.) or having known virulence
factors are not allowed. The strains should not produce
antibiotic substances that are relevant in human or veterinary
medicine, nor should they carry transmissible resistance
determinants against such antibiotics (see 3.4.1.5.).
3.4.1.1. Target Animal Safety
The target animal safety is established by the “tolerance”
test. In this assessment, the target animal is exposed to a
tenfold overdose of the final product (micro-organism and
the carrier). The test must be conducted with each of the
target species or animal categories for which the claim is
made. For example, tolerance tests performed on growing/
fattening pigs are not acceptable if the product is also
intended for piglets. The minimum test period is one month
(young, rapidly growing animals) but, for instance, dairy
cows have to be tested for a minimum of three months.
During the test, the animals should be routinely monitored
for adverse effects, performance characteristics and, when
relevant, for product quality. Autopsies and histopathology
are not required, but routine blood chemistry should at least
be included in the study.
The effects of the additive on the intestinal microflora
should be evaluated by enumeration of the routinely cultivable
microbial groups in the faecal flora (i.e., coliforms,
enterococci, clostridia, etc). Also, the intestinal survival and
the rate of disappearance from the faeces after withdrawal of
the additive should be monitored. In certain cases, effects on
the shedding of human enteropathogens may be required,
especially if the product is intended for companion animals.
3.4.1.2. Operator Safety
Microbial feed additives are mostly powder or granule
formulations. Therefore, exposure for the operator is most
20 Current Pharmaceutical Design, 2005, Vol. 11, No. 1 Atte von Wright
likely to occur via skin contact or inhalation. The formulated
commercial product should be examined for skin irritancy
using validated laboratory animal tests and, when appropriate,
also for eye irritation. Skin sensitisation tests are also
recommended, in case there is any reason to suspect that the
preparation contains components that may be able to penetrate
the skin. With respect to respiratory sensitisation,
microbial additives are regarded as sensitisers, unless there is
evidence to the contrary. Protective measures to minimise
the exposure are, therefore, recommended and specific studies
on the dusting properties and particle size are required in
order to estimate distribution of the inhalable fraction.
3.4.1.3. Consumer Safety
Consumer safety concerns arise from the ill-defined
fermentation products that may be present in the manufactured
goods. To exclude the possibility that these may
accumulate in the animal, and, thus form a consumer risk,
certain toxicological tests are required. These include both
gentoxicity studies and oral toxicity tests. The required
genotoxicity studies include a bacterial reverse mutation
ass