Post no 1366 Dt 20th August 2019
Compiled & shared by- DR RAJESH KUMAR SINGH, JAMSHEDPUR,9431309542,rajeshsinghvet@gmail.com
India is a highest milk producer in the world. Whereas the concept of qualitative milk for consumer is the most valuable things related to milk production and its processing. The quality of raw milk is the primary factor determining the quality of milk products. Good quality raw milk has to be free of debris and sediment; free of off-flavours and abnormal colour and odour; low in bacterial count; free of chemicals (e.g., antibiotics, detergents); and of normal composition and acidity. Physical contaminants like dirt particles, hair, leaves, rubber and mettle particles, paper pieces etc. can get entry in to the milk at the time of milking. Chemical contamination in milk comprise may introduce during milk production, dairy processing and packaging. Aflatoxins, pesticides and insecticides residue, antimicrobial residue, antibiotic residue and heavy metals residue are chemical contaminants that can enter to animal feed and they have some residue in milk. Hormonal residue such as steroid hormones and bovine growth hormones is an other type of contamination which exerting profound biological effects in animals and humans.
Milk production is indistinguishably linked to the environment. Animals may become exposed to antibiotics and chemical substances during their productioncycle. These antibiotic and chemicals have been identified to date could come from drugs aimed at treating diseases or application of chemicals for the control of weeds, insects, fungi and rodents in order to enabled agricultural productivity. These antibiotics and chemicals are environmental contaminants linked to atmospheric pollution, feed, soil and water. Uncontrolled and indiscriminating use interfering with the natural food delivering ecological system lead to residues in milk and result risk to human and environmental health. Residues which have been found in milk are antibiotics, antihelminthicdrugs, pesticides, fungicides, disinfectants, mycotoxins and heavy metals. Any of these compounds may persist at a collection, preparation processes of dairy products and they considered as residues. The key use of antibioticsis the treatment of infectious disease and to treat and prevent udder infections and as a growth promoter in the livestock industry.Unauthorized antibiotic use may result in residues of these substances in milk and meat.Antibiotic residues are small amounts of drugs or their active metabolites, which remain in milk after treating the animals. Because of the public health significance, milk and milk products contaminated with antibiotics beyond a given residue levelsis considered unfit for human consumption. In order to safeguard human health the World Health Organization (WHO) and the Food Agriculture Organization (FAO) have set standards for acceptable daily intake and maximum residue limits in food.A regulatory limit for antibiotic residues and other chemical residues imposed on the dairy industry in many countries. However, there is no regulation in India, especially for use of antibiotics in animals for treatment and as a growth promoter.
Sources of Chemical Contaminants of Milk
Most of the chemical contaminants in milk and dairy products are antibiotics, antihelminthic drugs, pesticides, disinfectants, mycotoxins and heavy metals.
- Veterinary drugs
Much of the veterinary treatment of dairy cattle involve the use of antibioticsin the infectious disease and to treat and prevent udder infections and as a growth promoter.Some drugs apply to control endoparasites, ectoparasites and to increase milk production. The most commonly used antimicrobials in dairy cattle can group into five major classes. These include the beta-lactams (e.g. penicillin’s and cephalosporin’s), tetracycline’s (e.g. Oxytetracycline and chlortetracycline), aminoglycosides (e.g. streptomycin and gentamycin), macrolides (e.g. erythromycin) and sulphonamides (e.g. sulfamethazine). Antihelminthic drugs, Oxyclozanide, Closantel, RafoxanideAlbendazoleand Ivermectin which are used to remove parasites such as flukes, tapeworms (cestodes), nematodes (round worms) and external parasites are important in animal production systems.
- Pesticides and insecticides
Chlorinated pesticides (DDT, BHC, lindane, dieldrin), Organophosphate pesticides (Parathion, Malathion) and carbamatecan enter milk and dairy products when the cow consumes contaminated feed.
- Mycotoxins:
Inappropriate temperature and moisture conditions such as when feeds are harvested damp, have not adequately dried, or are improperly stored some of the molds produce various toxic metabolites termed as mycotoxins. These metabolites may be hazardous to human and animal health.Animal fed with feed containing Aflatoxin B1 (AFB1) converted it into the Aflatoxin M1 (AFM1) and it secrets into milk.Heat treatments like pasteurization were not effective in the reduction of the formation of AFM1.AFM1 with different levels could be available in dairy products made from contaminated milk.
- Nitrates and nitrites and Heavy metals
Nitrates and nitrites are chemicals used in fertilizers, rodenticides (to kill rodents), and as food preservatives and Heavy metals mainly Lead (Pb) and cadmium (Cd)can enter to milk and dairy products and affect the health of people who have consumed contaminate milk and dairy products.
Antimicrobial residue———–
The most contentious residues that occur in milk are antimicrobial drugs. Much of the veterinary treatment of dairy cattle involves intra mammary infusion of antibiotics to control mastitis. Some drugs apply to control endoparasites, ectoparasites and several illnesses and to increase milk production (Korsrud et al., 1998.). The most commonly used antimicrobials in dairy cattle can group into five major classes. These include the beta-lactams (e.g., penicillins and cephalosporins), tetracyclines (e.g., Oxytetracycline, tetracycline and chlortetracycline), amino glycosides (e.g., streptomycine, neomycin and gentamycin), macrolides (e.g., erythromycin) and sulfanomides (e.g., sulfamethazines) (Mitchell et al., 1998.). Whenever any route with an antibiotic treats a lactating cow, measurable levels of the antibiotic are usually detectable in the milk for a few days after the last. There are Maximum Residues Limits (MRLs) for some drugs in milk according European Union (EU) regulations that have shown in Table 1 (European Commission, 1997).
Antibiotic residue————-
Although antibiotic residues in foods can have a detrimental effect on the processing of cultured products such as cheese and are important in terms of consumer confidence, the public health significance of residue concentrations of some of these compounds in foods from animals appears to be low, based on substantial scientific assessment. Most of the antibiotic drugs currently used in animal agriculture are relatively nontoxic, even at high concentrations, but there are a few antibiotics which pose a small but significant threat to public health when present in sufficiently high concentrations in foods. Among these is chloramphenicol, which has been associated (In a non-dose related manner) with a plastic anaemia due to bone marrow depression in a small proportion of human patients to whom the drug was administered for therapeutic purposes. Some of the patients who survive the bone marrow depression have developed leukemia, which creates concerns about possible carcinogenicity. Other antibiotics have been associated with allergic reactions of varying severity in people. An estimated four to ten allergic reactions occur per 100,000 courses of penicillin treatment administered directly to people, but actual incidents of allergic reaction to penicillin residues in foods are few and poorly documented. Although sulfonamides and tetracycline hydrochloride ministered to people at therapeutic concentrations may have toxic and allergic consequences. Based on experimental evidence, however, there is concern that residue concentrations of antibiotics have the potential to encourage the development of antibiotic resistance in the microbial flora of people eating contaminated foods.
Hormone residue in milk———-
Steroid hormones—–
Milk can also consider as a rich source of steroid hormones. The amounts of lipophilic hormones depend on the fat content of the milk and dairy products. Not only progesterone but also estrogen increases with fat content. Food processing does not seem to influence the amount and ratios of the hormones. In fresh cheese as well as in ripened cheese, testosterone was detected (0.1-0.5 mgkg-1 ). Probably not only propionic acid bacteria but also other fermenting bacteria or clotting enzymes are responsible for the formation of testosterone during the fermentation process.
Bovine growth hormones————–
Bovine Growth Hormone (BGH) or Bovine Somatotropin (BST) is a genetically engineered protein hormone either identical or similar to the natural bovine pituitary product. Its primary function is to increase milk production dairy lactating cattle. Therefore, BST is a protein hormone that increases milk production in cows between 10 and 15%. An increase in milk yield typically occurs with 5 days after beginning of treatment. When BSTtreated cows were consuming sufficient quantities of nutrients to meet the energy needs for additional milk synthesis, body lipid mobilization did not increase, but lipid synthesis was instead reduced. BGH increases activity and/or longevity of mammary secretary cells, probably via Insulin-like Growth Factor (IGF)-I produced by the liver and/or the mammary gland. IGF-I is a portion of the effects of BST on lactation in dairy cow (Etherton and Bauman, 1998). The raw milk and pasteurized milk could have been levels of IGF-I of 5.6 and 8.2 ng mL-1 , respectively. The infant formula could have been only trace amounts of IGF-I of 0.7 ng mL-1 . Therefore, IGF-I is not destroyed by the pasteurization process but the heating of milk for the preparation of infant formula denaturizes IGF-I and significantly, reduction (35-48%) levels of IGF-I compared to raw milk. BGH is probably stimulating immunological responses of animals and hence increasing the milk cell count. The US Food and Drug Administration (FDA) declared BGH officially “safe” in 1993, but it can cause to increase incidence of clinical mastitis in cows. This prompted concern that increased use of antibiotics to treat the mastitis might lead to increased residues of such drugs in milk. In news of the World Trade Organization has partially accepted European Union (EU) contentions for prohibiting the use of growthpromoting hormones in cattle.
Toxic Agents in Animals
Toxic Agents in the animal can enter through the multiple way like oral (e.g. mycotoxins, pesticides), dermal (e.g. external antiparasitic agents), parenteral (e.g. antibiotic treatment), inhalation (anaesthesia before surgical procedures) and by intra mammary and intrauterine infusions.All of these routes may lead to residues appearing in milk and dairy products. In lactating cow, measurable levels of the antibiotic are usually detectable in the milk for a few days after the last treatment.Risks to human health due to the consumption of contaminated milk and milk product by potentially toxic substances. Chemicals in the animal body go through a series of stages including absorption, distribution, metabolism and excretion, forming part of the pharmacokinetics or toxicokinetics.
Absorption and Distribution:
Absorption of toxic agent is depend on the route of the administration. After absorption, a toxic agent distributed throughout the whole body by the blood flows and stored in the fatty tissue because of their fat solubility.
Metabolism and Excretion
Metabolism of the toxic compound is occurred in the liver and make them less toxic and water soluble they are then excreted by the body but sometimes they are converted in more toxic form are termed as the bio activation (e.g. Aflatoxins). Toxicants eliminated from the body by various routes, the kidneys being the most important organ for excreting chemicals since it is the main elimination route. The other important elimination route is faeces and milk. Milk is an important elimination route due to its chemical composition, a lipid emulsion in an aqueous protein solution. Therefore there are Maximum Residues Limits (MRLs) for some drugs in milk that have been standardized. The withdrawal time is defined as being the time required after a drug administered to an animal to ensure that drug residues in marketable products (Milk, Meat, Eggs etc.) are below a determined maximum residue limit (MRL).
Methods for detection of antibiotics and chemical residues in milk
There isa variety of methods for reliably detecting, confirming and quantify a drug’s residues, which could be present in milk. These methods grouped into bioassays, microbiological assays, immunochemical assays and physical-chemical assays.
Public Health Concerns
Most of the antibacterial currently used in the control and treatment of farm animal diseases are relatively nontoxic even at higher concentration, but there are few antibiotics which pose a significant threat to public health when present in sufficiently high concentrations in milk. The presence of chemical contaminants in milk is very important for consumers and it can be a matter of public health concern as well as many of unknown diseases in human because of milk and dairy products are widely consumed by humans throughout the world.
Considering the issue of public health hazards, milk and milk products contaminated with antibiotics and other chemical contaminants beyond a given residue levels are considered unfit for human consumption. The residues of antibacterials may present pharmacological, toxicological, microbiological and immunepathological health risks for humans. This concerns primarily antibiotics in use as treatment and feed additives. Overuse of antimicrobial in livestock production cause to toxicity in human and animals. They can cause some disruptions like aplasia of the bone marrow (e.g. chloramphenicol), carcinogenic (e.g. furazolidone) and Penicillins have low toxicity but their most common adverse effects are hypersensitivity reaction, especially skin rashes, gastrointestinal disturbances diarrhoea, nausea and vomiting. Nitrofuranscan react with nitrite to yield (carcinogenic) nitrosamines, benzimidazoles or their metabolites causes embryotoxicity and teratogenicity. Tetracycline can generate bacterial resistance. The emergence of resistant bacteria within animals and the transfer of antibiotic resistance genes(R-factor)from non-pathogenic bacteria to other bacteria or human pathogens that will lead to widespread resistance. Apart from the health hazards, antimicrobial residues in milk are responsible for interference with starter culture activity and hence disrupt the manufacturing process of milk products. The acute and malicious consumption of pesticides involving higher dose results in death whereas, chronic insidious intake lead to elevated cancer risk and disruption of body’s reproductive, immune, endocrine and nervous system. Mycotoxins can also present in milk and dairy products and can create public health problems in humans. Aflatoxin M1 in milk is a carcinogenic metabolite of Aflatoxin B1. Aflatoxin M1 in milk and dairy products led to increasing the risk of liver cancer (hepatocellular carcinoma).
Exposure to higher levels of nitrates or nitrites has been associated with increased incidence of cancer in adults, and increased incidence of brain tumors, leukemiaand “blue baby syndrome” (methemoglobinemia) in children.The health implications from heavy metals lead to kidney damage, brain damage cardiovascular diseases, growth inhibition, interference in haemoglobin synthesis, and also some of these residues are known to be carcinogenic in nature.
Regulation and Risk assessment
The regulation of illegal residues in foods is a cooperative effort of FSIS (Food Safety and Inspection Services), FDA (Feed and Drug Administration) and EPA (Environmental Protection Agency). In India, Food Safety and Standards Authority of India (FSSAI) under the Ministry of Health and Family Welfare is the main authority for establishing the scientific standards for articles of food including milk and milk products and to regulate their manufacture, storage, distribution, sale and import, to ensure availability of safe and wholesome food for human consumption under the rules specified by Food Safety and Standard Act, 2006. To avoid risks related to Veterinary drug residues in milk, in many countries maximum residue limits (MRLs) have been established for each antibiotic and chemical substances. Milk withheld from sale for a specific period after veterinary therapy (usually 72-96 h) to ensure that no residues persist.
MRLs for some commonly used antibiotic drugs and chemical residues in milk according to Indian regulations.
Training_Manual_Veterinary_Drug_Residues_24_04_2018 (1)
HACCP is a quality managementprogram to identify hazards and to determine the acceptable limits in the production process.
Possible strategies for prevention of antibioticsand chemical residuesin Indian scenario
Chemical contaminants in milk and dairy products are results of environmental contamination, poor veterinary service and misuse ofantibiotics, uncontrolled use of pesticides and insecticideingested by animals.Chemical contamination not completely prevented, or eliminated from milk and dairy products.However, the implementation of food safety andregulatory laws can reduce chemical residues in milk and dairy products.
Possible strategies to prevent residues in milk:-
- Good hygiene and management practices at farm prevent the spread of disease among livestock which could reduce the need for antibacterial use. 2) Alternative use of antibiotic growth promoter e.g. probiotic microorganisms, immune modulators, organic acids and other feed supplements. 3) Avoid using antibiotics in the veterinary field without a veterinarian’s prescription. 4) Educate dairy owners on drug withdrawal period of treated animals. 5) Development and validation of rapid screening tests for detection of antimicrobial residues in milk 6) Establishing the policy for use of antibacterial in animals will help monitoring and surveillance of the usage of these drugs. 7) Pharmacovigilance programme would be developed for veterinary pharmaceuticals for the risk assessment of antibacterial drug residues for human and environment. 8) Strict national legislation passed on livestock sector to avoid unnecessary use of chemicals. 9) National chemical residues control and monitoring program should be designed to set standards on the use of chemicals (antimicrobials, insecticides, pesticides, etc.). 10) Training to farmers and personnel about good manufacturing practices and monitoring are useful to reduce chemical Ucontaminants in milk and dairy products.
Milk is considered a complete food because it contains proteins, fat, carbohydrates, minerals, vitamins and water. The quality of milk can be affected due to physical and chemical factors. Whereas milk produced under good handling practice from production, processing and up to consumption has good quality and its physicochemical composition. Physical contamination of milk can prevent with good practices but chemical contamination cannot completely prevent because it will find in fat or lipophilic contaminants. The use of food safety management and quality assurance in milk production and processing plant can much reduces the physiochemical contaminants in milk and milk products.
