Transmissible spongiform encephalopathies
Feed and feed ingredients should be obtained and preserved in a stable condition so as to prevent hazardous effects due to contamination or deterioration. When received, feeds should be in good condition and meet generally accepted quality standards. Preservation can be facilitated by low temperature storage, ensiling, dehydration or the addition of appropriate chemicals (e.g. propionic acid). Furthermore, pasteurization reduces the numbers of most pathogens. Maintaining low water activity (i.e. Aw <0.65) will minimise bacterial and fungal growth.
Good Manufacturing Practices (GMPs) should be followed at all times. Specific control measures for identified hazards are listed below.
Þ All tissues from cattle with clinical BSE should be incinerated so that they are eliminated from all feed and food chains.
Þ In countries where BSE has occurred, depending on its incidence 1, consideration should be given to placing restrictions on the use of meat and bone meal derived from specific bovine tissues in ruminant feeds. A similar consideration should be made in countries where a risk assessment indicates that the cattle population has been exposed to infection.
1 As determined by a competent authority using an appropriately structured surveillance programme.
Þ In countries where BSE and sheep scrapie have occurred, consideration should be given to placing restrictions on the use of ruminant derived protein from the feeds of ruminants.
Þ In countries where BSE has not occurred, but where sheep scrapie is present, consideration should be given, dependent on the incidence of scrapie and the time/temperature processes used for the rendering of ovine carcasses and tissues, to placing restrictions on the feeding of ovine derived protein to ruminants.
Þ The measures listed above may require re-evaluation in the light of future research findings on the inactivation of TSE agents during rendering.
Þ Cross contamination of cattle feeds with meat and bone meal produced from the rendering of potentially infected cattle tissues should be prevented.
Þ Salmonella enterica, Toxoplasma gondii, Trichinella spiralis are sensitive to heat and are readily killed if the manufacture of feed involves pasteurization.
Þ Protocols developed for GMP must include measures which prevent recontamination of heat treated feed by these agents.
Þ Only products licensed for administration to food producing animals should be used and the withholding time should be observed before milk or eggs are used for food or animals are sent for slaughter. Adherence to the Codex Code of Practice and Guidelines for Control of the Use of Veterinary Drugs and of Veterinary Drug Residues in Foods (CAC/RCP 38-1993) will ensure animal feeds do not contribute to excessive veterinary drug residues in foods.
Þ It is essential that the levels of agricultural chemicals in feed are sufficiently low that their concentration in food is consistently below the established maximum residue limits such as those limits established by Codex.
Þ Feeds contaminated with mycotoxins in excess of established national maximum levels or international established maximum levels such as those established by Codex, should not be fed to animals producing milk, eggs or other tissues used for human consumption.
Þ Grain and cereals should be stored under conditions of low moisture. Mould inhibitors can be added to reduce fungal growth.
Þ Mycotoxin contaminated grains can be used for alternative purposes such as alcohol production, but by-products that result should not be fed to food producing animals.