Page 145 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

112 SECTION | I General

VetBooks.ir source for contamination of nonmedicated feedstuff with density (carrier, substance), and electrostatic properties.
The cross-contamination decreases according to the prod-
medicated feed rations is the way in which it is manufac-
uct being less adhesive and electrostatic (EFSA, 2007).
tured and handled at the feed mill, where it is likely that
within a short period of time, both medicated and nonme- The legal basis of this technological process is based on
dicated batches will be milled and pelleted. The prepellet- Regulation (EC) No. 183/2005 (EC, 2005), which replaced
ing bins, and the pelleting die, were identified as the most Council Directive No. (EC) 95/69 (EC, 1997). Article 10 of
likely reservoirs of contamination, and feed handling at Regulation No. (EC) 183/2005 and provides that feed busi-
the mill was changed as a consequence. Following this, ness operators shall ensure that establishments under their
the number of feed batches containing more than 5% control are approved by a competent authority in case these
of the therapeutic dose of monensin dropped from 22.5% establishments are manufacturing and/or placing on the mar-
to 2.5% (Kennedy et al., 1998). Certainly, the origin of ket coccidiostats and histomonostats, or premixtures con-
contamination of feedstuff may be located at any point taining coccidiostats and histomonostats.
along the production and distribution chain, from the Carryover has been evaluated (Strauch, 2002, 2003;
point of manufacture at the feed mill to the moment of Dorne et al., 2011). Regular investigations have been per-
administration and use on a farm. formed with some coccidiostats, involving lasalocid and
This unavoidable carryover may occur at all stages of nicarbazin as well as sulfadiazine (McEvoy et al., 2003;
production and processing of feed but also during storage Noser et al., 2006). These investigations showed the
and transport to feed localization (EFSA, 2007) although persistence of these compounds in various feed batches
there are limited data on the amount and frequency of produced after the intentional incorporation of a polyether
contamination of food with residues of coccidiostats ionophore coccidiostat into the feed. The health risk
resulting from feeding cross-contaminated feed stuffs to to nontarget species resulting from the consumption of
food-producing animals (Dorne et al., 2011). In conclu- cross-contaminated feed with coccidiostats at levels of 2%,
sion, it can be either horizontal transfer and residue deple- 5%, or 10% was evaluated recently by the European Food
tion of veterinary medicinal products in broiler chickens Safety Authority (EFSA) and a revision of the RAs per-
and horizontal transfer and residues in dairy milk follow- formed can be found in the paper of Dorne et al. (2011).
ing the use of medicated feeds (e.g., sulfamethazine, Overall, the toxic syndromes in nontarget animal species are
chlortetracycline). related to: (1) accidental consumption of fortified feeds (in
In order to protect animal health, human health and most cases intended for chickens) by other animal species;
the environment, maximum levels of carryover for active (2) feed-mixing errors or ingestion of premix concentrates
substances contained in medicated feed should be estab- with unsafe amounts of ionophores; (3) off-label (extra-
lished, based on a scientific RA and taking into account label) use, either accidental or intentional, which have
the application of good manufacturing practice and the resulted in adverse reactions in adult poultry (laying hens),
ALARA (As Low As Reasonably Achievable) principle. ostriches, ornamental and game birds, and humans; and (4)
Cross-contamination of feed batches can result in the drug interaction with other veterinary medicinal products
exposure of nontarget animals and induce adverse health (target and nontarget animal species) (Dorne et al., 2011).
effects in these animals due to a specific sensitivity of To avoid unintended contamination of animal feed
mammalian species as compared to poultry. Residue for- and thereby animal products by veterinary drugs and feed
mation in edible tissues of nontarget species may result in additives, several measures need to be integrated. The
unexpected human exposure through the consumption of internal control of the producers who manufacture their
animal products (Dorne et al., 2011). Feed additives, such own medicated feed stuffs, the animal farming, the busi-
as coccidiostats (polyether and nonpolyether ionophores) ness, the slaughterhouse, and the animal processors and
for poultry, are marketed as premixes, intended to be retailers have to maintain a documentation system provid-
incorporated into mixed feeds during the mixing and pro- ing full transparence of the food safety issues (i.e., quality
duction process. The degree of carryover depends on the and safety of their animal products). One important con-
technical facilities and procedures as well as on product trol point in this system is the absence of the drug in non-
characteristics. For example, the physicochemical charac- target animal feed and target-animal. The key aspect in
teristics of feed additives can contribute to cross- avoiding cross-contamination on nontarget animal feed by
contamination. The electrostatic properties of some drugs, therapeutics is the introduction of reliable traceability sys-
particularly those in powder form, aggravate the problem, tems, including clear labeling and the control of all feed
making it more difficult to clean equipment between ingredients used in the animal feed production line.
batches (Hurd, 1996). The feed additives and premixes Technical improvements can reduce this cross-
also have an important influence on cross-contamination contamination considerably and hence limits of cross-
behavior, having the following properties of importance: contamination can be defined per product to exclude any
adhesion strength—adhesion to walls, particle size and health risk for human and nontarget animal species.