SESSION 2 B. Managing the feed supply
Abstract
Animal feed production is growing rapidly to sustain the growing demand for animal products. World animal feed production is 597 million tons per annum. The production of dairy products follows the trends in demand and the production systems vary from sophisticated intensive systems to backyard small-scale farming. Feed safety and quality is essential in maintaining the quality of animal products. Potential hazards associated with animal feed includes mycotoxins, infectious agents such as Salmonella, E.coli and Transmissible Spongiform Encephalopathies (TSEs), residues of veterinary drugs, antimicrobals and environmental and industrial contaminants. The feed chain includes the sourcing, processing and storage of feed raw materials, all posing some degree of risk towards contamination or quality deterioration. The Code of Practice for Good Animal Feed Production is essential to control any risks of feed borne hazards and that includes the assessment of risk and the adherence to international standards such as stipulated by the Expert Consultation Group for Codex.
INTRODUCTION
Raising animals, to produce meat, milk and eggs is nothing new to the human race and has been taking place for centuries. Livestock production is growing rapidly due to an increase in demand for animal products. Global milk production have risen from 526 million tons in 1992 to 598 million tons in 2002 (FAOSTAT 2002). World animal feed production is 597 million tons to sustain current animal production.
Technology continuously advances making life more sophisticated each day. Raising animals and feeding them for the production of food will always be a fundamental activity for humans to sustain life. Currently, one third of protein in the human diet comes from products of animal origin and its is believed that more would be positive. Increased consumption of animal protein by children has been associated with improvements in both physical and mental development (Bradford, 1998).
It is expected that increases in animal products consumption will occur in developing countries in contrast to developed countries, which have a stable consumption. Growth in meat, milk and eggs has occurred primarily in areas where affluence is increasing. Increasing disposable income allows the substitution of vegetable product diets with animal protein.
Well-informed societies have become very focused on food issues, to the point at which concern for the danger of food safety has risen to the limits of scientific possibility. There is considerable variation in the regulation of animal production and feed industries in various countries making it impossible for a common set of standards. It is however imperative that the safety of the consumer is not compromised at any stage in any country.
The safety of food from animal origin begins with safe animal feed. Feed manufacturers, farmers and food operators have the primary responsibility for food safety.
INTERNATIONAL TRADE
It is essential that with respect to food safety the sanitary and phytosanitary measures are applied to protect human and animal health and not applied as a means of arbitrary or unjustifiable discrimination between countries where the same conditions prevail. Food safety should not be a disguised restriction on international trade. There is agreement throughout the international community that food safety measures should be scientifically justified.
POTENTIAL HAZARDS ASSOCIATED WITH ANIMAL FEED
Mycotoxins
Mycotoxins are secondary metabolites produced by fungi of various genera when growing on agricultural products before or after harvest or during transportation or storage. Mycotoxins pose a risk both to animal production and human health. Mycotoxins have various chemical structures resulting in a variety of negative effects such as being carcinogenic, estrogenic, neurotoxic, dermonecrotic, or immunosepressive.
Mycotoxins are metabolised by animals significantly reducing the risk of exposure to these toxins during the consumption of animal products. Mycotoxins or their metabolites can be found in meat, visceral organs, milk and eggs at much lower levels than in the feed consumed by animals and are highly unlikely to cause acute intoxication in humans. The ability of various animal species to metabolise mycotoxins differs considerably; pigs are more sensitive than poultry, which in turn are more sensitive than ruminants.
Mycotoxins are found mostly on feed ingredients such as maize, sorghum, wheat and groundnut s. The main risk for mycotoxin consumption by humans is cereal grains and legumes. The risk for humans consuming these products containing mycotoxins is much higher than from animal products.
Reduction of mycotoxin contamination at each critical point in the chain from crop grower to storage handler, feed mill operator and livestock producer must be striven for. Mycotoxins can not be totally eliminated from feed and processing of animal feed such as heat treatment has little effect on mycotoxin contamination and risk cannot be reduced in this manner. Continuos monitoring of levels needs to take place to ensure contamination is within acceptable tolerance levels.
Preventing contamination at source is one of the most effective methods of reducing the risk of mycotoxins. To prevent contamination we need to apply appropriate technology in crop production, handling, storage and processing in addition we need to apply measures aimed at decontamination and measures to prevent marketing of contaminated feed or raw materials.
INFECTIOUS AGENTS
Salmonella
There are over 2000 salmonella serotypes and these can be divided into three unequally sized groups. Firstly the specie specific serotypes such as S. dulin (cattle) and S. gallinarium and S. pullorum (poultry), secondly the invasive serotypes which may cause septicaemic disease in several animal species, these include S. enteritidus and S. typhimurium, thirdly the non-invasive serotypes which tend not to result in septicaemia. Group one are not recognised as feedborne pathogens. The third is by far the largest group and may be associated with subclinical infections in farm livestock. They can occasionally cause disease and are associated with food poisoning in humans. The principal manifestation of human salmonellosis is gastro-enteritis. Septicaemia occurs in a proportion of patients. The young, old or immunocompromised are the most susceptible to salmonella.
Salmonellae are widely distributed in nature, and feed is only one of many sources for farm animals. Feed ingredients, of both animal and plant origins are frequently contaminated with salmonellae although the most common serotypes isolated are rarely the most prevalent in animals including man. The two most important serotypes associated with human disease, S enteritidis and S. typhimurium are rarely isolated from feed.
Poultry meat is still considered to be one of the main sources of Salmonella infections in humans. Approximately 20% of raw poultry on retail sale in the UK are reported to contain Salmonella. (Liebana et al., 2002).
Improved hygiene and biosecurity have considerably reduced vertical transmission of S. enteritidis is has resulted in horizontal transmission from the farm, dairy or feed, have become relatively more important (Angen et al., 1996).
TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES (TSES)
TSEs in ruminants are non-febrile neurological diseases of man and many animal species including ruminants. TSEs are associated with incompletely defined agents, currently termed prions, which are resistant to normal heat treatment of feed and food. Sheep scrapie has been recognised for over 250 years, while Bovine Spongiform Enchephalopathy (BSE) was first recognised in the United Kingdom in 1986. For BSE it has been postulated that the tissue of the central nervous system and of the reticuloendothelial system under conditions of insufficient heat treatment act as infectious agent via the feed. The reported occurrence of a new variant of the human TSE, Creutzfeld-Jacob Disease (CJD) has raised the possibility of a link between BSE in cattle and CJD in human through the consumption of meat from BSE infected cattle. (FAO, 2001).
VETERINARY DRUGS
Veterinary drugs may be administered in animal feeds. If the concentration used results in foods of animal origin exceeding the Maximum Residue Limits (MRL’s), there may be a potential hazard to human health. MRL’s should not be exceeded if concentrations used are correct and withholding times are observed.
ANTIMICROBIALS
World wide government regulatory agencies, consumer groups, doctors, veterinarians and animal health industry are calling the “prudent use” of antibiotics. Prudent use policies as they relate to animal agriculture have three basic principles:
- Animal management practices to raise animals should be adapted to decrease the need for antibiotics that are important to human health.
- Therapeutic antibiotics should be used judiciously and sparingly. The correct antibiotic for the disease problem should be used and it should be used correctly (dosage, duration, withdrawal etc.).
- The use of narrow-spectrum, rather than broad-spectrum antibiotics should be advocated whenever possible.
- A potential concern with feed additive antibiotics is residues. Feed additives that result in residues should not be used in animal feed. Scientific data such Froyshow et al (1983) on the absorption, metabolism and excretion of specific antibiotics is imperative.
ENVIRONMENTAL AND INDUSTRIAL CONTAMINANTS.
The hazards include herbicides, pesticides and fungicides and other extraneous contaminants such as polychlorinated biphenyl’s (PCBs) and heavy metals. Programmes that adequate analytical expertise and equipment must support monitor and control levels of environmental and other chemical contaminants in food and feed.
Few laboratories around the world are equipped to test for compounds such as dioxins as was experienced during the crisis in Belgium a few years back. Testing methods need to be elaborated, acceptable levels need to be determined and reviewed continuously.
ASSESSMENT OF RISK
The Expert Consultation group for Codex provided a risk assessment for foodborne hazards entering the food chain via feed. The risk assessment included hazard identification, hazard characterisation, exposure assessment and risk characterisation. They concluded that there are risks arising from foodborne hazards that enter the food chain via feed. The risk of these hazards was low in comparison to foodborne hazards that originate from other sources. The risks from salmonellae are considerably greater during processing of carcasses and subsequent processing. The threat from mycotoxins is far greater from eating contaminated cereal grains than from eating foods derived from animals fed contaminated grains (FAO, 1997).
CONTROL OF FEEDBORNE HAZARD
The following practices will aid in controlling feed borne hazards:
- Good Manufacturing Practice (GMP) should be followed at all times. GMP has become the minimum standard for all major feed producing countries around the world. The GMP will ensure feed ingredients should be obtained and preserved in a stable condition.
- Meat and bone meal derived from ruminant animals should not be fed back to ruminants to prevent the possible transmission of BSE.
- Salmonella are sensitive to heat and readily killed if the manufacture of feed involves a process with sufficient heating.
- Only veterinary drugs licensed for administration to food producing animals should be used and withholding time should be observed before animals are sent for slaughter.
- Agricultural chemical levels in feed need to be sufficiently low that their concentrations in food are consistently lower than MRL.
- Feeds contaminated with mycotoxins in excess of acceptable levels should not be fed to animals producing milk, eggs or other tissues used for human consumption. Grains and cereals should be stored under conditions of low moisture.
GENETICALLY MODIFIED ORGANISMS
Genetically modified organisms (GMO’s) are a fact of modern agriculture, and are here to stay. Public awareness with respect to GMO’s has to be taken into account and communication on the ramifications of GMO’s on not only food safety but also food security is essential. The control of the use of GMO technology is essential; approval of specific crops, genes, ecologies and production systems is of vital importance to ensure health and environmental safety, thus commanding public support.
The total area planted to GMO crops in the world is currently estimated at 44.2 million hectares having increased four times over the last 3 years (Fresco, 2001). The major percentage of these plantings are soybean, maize, cotton and canola, with insect resistance and herbicide tolerance the main traits. Several thousand GMO field tests throughout the world are underway, mostly in industrialised countries. Over 200 crops are currently under field testing in developing countries, Latin America 152, Africa 33 and Asia 19. The number of GMO’s that can be expected to released for commercial use of the next few years can be expected to increase substantially (Fresco, 2001).
There has to date been no proven effect of GMO’s on human life to spite having been around for many years. Lack of evidence of the effect of GMO’s on health and the environment may not be proof that genetic modification is safe. Evidence suggests that GMO (bt) maize has a reduced risk of fumonisin contamination when compared to conventional maize grown under the same conditions thereby reducing the risk of negative effects from mycotoxins (Munkvold and Hellmich, 1999).
Thorough risk-assessment of individual GMO’s effect on food, health and the environment should be conducted before specific GMO traits can be approved. Generalisations about GMO’s should be discouraged and reference should be made to specific crops, genes, ecologies and production systems. The use of not only national resources by individual countries but international assessments to avoid duplication, economise on time and save costs must be investigated.
CODE OF PRACTICE FOR GOOD ANIMAL FEED PRODUCTION
A code of practice for good animal feed production (GMP) constitutes an important preventative approach to feed safety. The GMP covers use of additive, handling and storage, methods during manufacturing, labelling, tractability and record keeping. It is essential that all feed manufacturing adhere to a GMP.
CONCLUSION
Certain chemical substances and biological agents incorporated into feed, either intentionally or unintentionally, can result in hazards in food of animal origin and may enter feed at any stage of production up to the point of feeding.
The hazards to human health associated with animal feeding are relatively minor in comparison to food borne hazard from other sources.
The management of risk from food borne hazards which originate in feed need to be weighed against the potentially greater risk that would result from an inadequate or overly expensive food supply as well as the environmental risk that would result from failure to recycle nutrients.
Good Manufacturing Practice is an essential tool to providing safe feed for safe food.
Thorough risk-assessment of individual GMO’s effect on food, health and the environment should be conducted before specific GMO traits can be approved.
REFERENCES
Angen, O., Skov, M.N., Chriel.,M., Agger, J.F., and Bigaard, M.1996. A retrospective study on Salmonella infection in Danish broiler flocks. Preventative Veterinary Medicine, 26:223-237.
Bradford, G.E. 1998. Contributions of Animal Agriciulture to the quality of human life. Pp 171-188. Special Symposium & Plenerary Sessions, 8th WCAP, Seoul.
Delgado, C., Rosegrant, M., Steinfeld, H., Ehui, S. and Courbois C. 1999. Livestock to 2020: The Next Food Revolution. International Food Policy Research Institute, Food, Agriculture, and the Environment Discussion Paper No. 28 p72.
FAO. 2001. Action on Animal Feed Safey. International Conference and World Forum on TSE/BSE Cairo Egypt 1 to 4 May 2001 p5.
FAO.1997. Animal feeding and food safety. Report of an FAO Expert Consultation, Rome, Italy, 10 to 14 March 1997 p4.
IDF/FAO international symposium on dairy safety and hygiene Cape Town,
2–5 March 2004,
South Africa |
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