The first step in residue prevention is to make individuals and organisations aware of the problem through education by veterinary personnel, organisations, literature and governmental agencies. There must be rapid screening procedures for the analysis of antibiotic residues and instant grading and prohibition of food containing antibiotics more than the minimum residue level
Use of antibiotics that could lead to deposition of their residues in meat, milk and eggs must not be permitted in food intended for human consumption.
If the use of antibiotics is necessary to prevent or treat animal diseases, a withholding period must be observed until the residues become negligible or are no longer detected.
The use of antibiotics to bring about improved performance in growth and feed efficiency and to control the reproductive cycle and breeding performance also often leads to harmful residual effects.
Concern over antibiotic residues in food of animal origin is of two types. One, it produces potential threat of direct toxicity in humans while, on the other, the low levels of antibiotic exposure could result in alteration of microflora, cause disease and possible development of resistant strains, which cause failure of antibiotic therapy in clinical situations.
A withdrawal period is necessary to safeguard humans from exposure to antibiotic added food. The withdrawal time is the time required for the residue of toxicological concern to reach a safe concentration that is tolerable. It is the interval from the time an animal is removed from medication until the permitted time of slaughter.
Heavy responsibility is placed on the veterinarian and livestock producer to observe the withdrawal period for a drug prior to slaughter to assure that illegal concentration of drug residue in meat, milk and eggs does not occur. Use of food additives is capable of improving feed efficiency by 17 per cent in cattle, 10 per cent in lambs, 15 per cent in poultry and 15 per cent in swine. But their indiscriminate use will produce toxicity in the consumers.
The World Health Organisation and Food and Agriculture Organisation have established tolerances for drugs, pesticides or other chemicals in the relevant tissues of food producing animals. The tolerance is the tissue concentration, below which a marker residue for the drug or chemical must fall in the target tissue before the animal's edible tissues are considered safe for human consumption.
Tolerances are established based on extensive toxicological studies of potential hazards of consumption to humans.
Antibiotics as growth promoter: Antibiotics nowadays are used to improve growth performance, especially in broilers, and as fatteners.
They may produce improved growth rate because of thinning of the mucous membrane of the gut, facilitating better absorption, altering gut movement to enhance better assimilation, and producing favourable conditions forthe beneficial microbes in the gut of animals by destroying harmful bacteria.
Antibiotics also favour growth by decreasing the degree of activity of the immune system, reducing waste of nutrients and lowering toxin formation. In most of the cases, only young growing animals and poultry are responsive to antibiotic mediated growth promotion.
Antibiotics in therapeutics: Indiscriminate use of antibiotics in all cases of fever, inflammation, wounds and viral diseases creates widespread residual effects on edible tissues.
The use of antibiotics only in specific conditions is justified because the role of microbial agents is mainly to kill the rapidly dividing invading cells.
Antibiotics in preventing disease: Animals and poultry are given sub-therapeutic levels of antibiotics to prevent possible infection.
But the antibiotics are specific to their spectrum of activity only in the actively multiplying stage of bacteria.
But it will not provide overall protection. Only in certain cases like dry cow therapy and surgical procedures is antibiotic prophylaxis necessary.
Antimicrobials are used either directly or indirectly during the production process and storage of milk and milk products. Direct contamination of milk may occur from air and water during processing, storage and transportation. Besides, feed given to animals is also a source of indirect contamination. Man will be the ultimate consumer of these antibiotic residues.
There are other reasons behind the use of antibiotics.
Lack of awareness and extension activities, inadequate literature supplied by manufacturers, absence of safer drugs, and the tendency to produce and profit more from animals. The extra label use of chloramphenicol, furazolidone, nitrofurazone, sulphonamide drugs, and flouroquinolones in lactating animals is prohibited.
Antibiotic residues in food produce pathological effects. There could be transfer of antibiotic-resistant bacteria to humans. Antibiotic residues could lead to immunopathological effects; autoimmunity, which is the system of immune responses of an organism against its own healthy cells, tissues and other body normal constituents;- carcinogenicity; mutagenicity or the capability to induce mutations, injury to the liver or impairment of the liver function, reproductive disorders, bone marrow toxicity and allergy.
The first step in residue prevention is to make individuals and organisations aware of the problem through education by veterinary personnel, organisations, literature and governmental agencies. There must be rapid screening procedures for the analysis of antibiotic residues and instant grading and prohibition of food containing antibiotics more than the minimum residue level.
Processing of milk helpsto inactivate antibiotics.
Refrigeration causes penicillin to disappear. In pasteurisation, most of the antibiotics will lose their activity.
Use of activated charcoal, resin and UV irradiation also helps in making antibiotics inactive.
Irrational use of antibiotics in field veterinary practices should be avoided.
There is a need to develop simple and economic field test to identify drug residue in edible animal products.
Ethno-veterinary practices could be promoted. Nationwide monitoring and periodic surveillance of microbial residue in edible tissues and milk must be promoted.
A version of this article appears in the print on November 24, 2021, of The Himalayan Times.