Standards for milk and milk products in international trade are established by the Codex Alimentarius Commission (Codex) (8,12,18). Codex was formed in 1962 to implement the Joint FAO/WHO Food Standards Program in an effort to protect the health of consumers and ensure fair practices in the food trade. The purpose of Codex is to facilitate trade not restrict it. Standards developed by Codex are to be based on scientific knowledge. Codex committees of note to the dairy industry include the Committee on Milk and Milk Products (CCMMP), the committee on Food Additives (CCFA), the Committee on Food Hygiene (CCFH), the Committee on Pesticide Residues (CCPR) and the Committee on Residues of Veterinary Drugs in Food (CCRVDF). The International Dairy Federation, with headquarters in Brussels, Belgium, is the official technical advisor to the CCMMP and makes significant input to all the Committees listed above.
As a result of the Uruguay Round of the General Agreement on Tariffs and Trade (GATT), the World Trade Organization (WTO) was formed (1) and of the agreements which have significance to the international trade of milk and milk products is the Agreement on the Application of Sanitary and Phytosanitary Measures (SPS) and the Agreement on Technical Barriers to Trade (TBT). The TBT agreement addresses items such as product standards, labeling and packaging. The SPS agreement deals primarily with issues of food safety with emphasis on food additives, pesticide residues, residues of veterinary drugs, and hygiene. Codex standards are recognized in the SPS Agreement as being the benchmark for the evaluation of compliance of national measures with the international provisions of GATT.
International Standards, Export Markets, and the US
Historically, the production sector of the U.S. dairy industry has expressed little interest in matters such as Codex standards, the WTO and the SPS Agreements. The dairy industry in the US primarily has been one of production for the domestic market and the US has not been a major player in the dairy export market, despite the fact that the US is the single largest dairy producing country in the world. The leaders in the international export market are the European Union (EU) and New Zealand. As a result of GATT and the North American Free Trade Agreement (NAFTA), the U.S. dairy industry’s interest in the export market seems to be increasing (14). An additional item that fuels this interest is the phasing out of dairy price supports in the US and the movement to a free market economy in milk by the first decade of the 21st century.
Why is the U.S. dairy industry not more aggressive in the international trade of dairy products? We would suggest that the U.S. dairy industry will attempt to aggressively pursue the export market as the US industry moves to a free market economy. Mexico, and many of the countries of Central and South America are currently major importers of dairy products from the E.U. and New Zealand (1,11). The countries of Argentina, Chile, Uruguay are developing strong dairy industries that are beginning to compete for the export market and will represent increasing competition to the U.S. Brazil is a major importer of dairy products but long term forecasts seem to indicate that Brazil has the potential to become an exporter of dairy products. The Pacific Rim countries (13) are currently major importers of dairy products and these markets will very likely continue to expand for dairy exporting countries. Currently, New Zealand and Australia are the major players in that part of the world.
Dairy producers in the U.S. will need to become increasingly aware of food safety standards as defined by Codex as we are now participating in a global industry. Heeschen (6) has stated that, "food safety is determined by hygienic requirements, which vary between categorical postulates for protecting human health and desirable properties, which are from the nutritional or aesthetic point of view conducive for optimal consumption". The major food safety criteria for milk and milk products are:
All of these issues are discussed within the National Mastitis Council as important for the production of quality milk and the safety of the consumers. One item that is not specifically mentioned is milk somatic cell counts. Currently no Codex regulation exists regarding an acceptable upper limit for the SCC in milk intended for trade on the international market. However, an effort is currently underway within Codex to establish such a standard. Within the E.U., milk somatic cell counts are encompassed within the term, "hygienic requirements". The E.U. adopts the position that all the measures necessary to obtain milk and milk products with a high hygienic standard are summarized in the term "food hygiene" (5,6,7).
Milk somatic cell counts are an issue in the international trade of milk and milk products and this was a major issue between the U.S. and the E.U. in the spring of 1997. The problem is that the U.S. has the highest upper limit for SCC (750,000 cells/ml) of all the major developed dairy producing countries of the world. The E.U., New Zealand, Australia, Switzerland, and Norway all accept 400,000 SCC as the upper limit and New Zealand may consider adopting 300,000 cells/ml in the future. Canada has now agreed on 500,000 SCC throughout all of the provinces and is already investigating the possibility of going to 400,000 cells/ml. This clearly leaves the U.S. in an unenviable position in the international market place of having to defend the concept that U.S. dairy products are as safe and as high quality as products from any other country. The U.S. media often states that U.S. dairy products are the safest in the world. Where is the proof of this statement? The U.S. position is that SCC are an issue of quality but not safety. This view is not shared by the E.U. due to the broader view and interpretation of "hygienic requirements" (5,6,7).
We would all agree that somatic cells present in milk are not a risk factor for human safety but the somatic cell count is a measure that might reflect health issues. Mastitis is an inflammation of the mammary gland and SCC are the most universally accepted measure of that inflammation. Almost all mammary gland inflammation is caused by the presence of a microorganism (an intramammary infection). Most mastitis research workers would agree that uninfected cows will have SCC less than 200,000 cells/ml and that SCC someplace between 200,000 cells/ml and 300,000 cells/ml are indicative that the cow is infected (16). SCC are clearly associated with quality (16,19). Diminished cheese yields have been reported as SCC increase from 100,000 cells/ml to 500,000 cells/ml and significant quality effects may be noted at SCC as low as 250,000 cells/ml. Bulk milk SCC have three broad uses. They are used to monitor the prevalence of mastitis in dairy herds; as an indicator of raw milk quality to processors; and as a more general indicator of the hygienic conditions of milk production on farms. Regulators in the U.S. seem not to be accept SCC as a general indicator of hygienic conditions on farms.
Bulk tank SCC are a function of the percentage of quarters infected by major pathogens in a dairy herd as demonstrated by Eberhart, Hutchinson, and Spencer in 1982 (3). These researchers reported a linear relationship between bulk tank SCC and the percent quarters infected with major pathogens. Based on the relationship they discovered, the percent quarters infected would be 6.2, 12.8. 24.3, and 32.6 for bulk tank SCC of 200,000, 400,000, 750,000, and 1,000,000 cells/ml, respectively. At the U.S. upper limit for SCC of 750,000 cells/ml, approximately 25% of quarters are infected by major pathogens. Another way to express this is that every cow in the national herd could be infected in one quarter with a major pathogen and we would be willing to accept the milk produced as "normal". Would US consumers be comfortable with this knowledge?
Bulk tank SCC are also used as an indicator of hygienic conditions of milk production and particularly in the E.U. (7). In general, the hygienic conditions on farms producing low SCC milk are more desirable than conditions on farms producing high SCC milk. A statement made on many occasions at past NMC Annual Meetings is that one can look at the condition of the front gate of any given dairy farm and accurately predict the bulk tank SCC. All aspects of management generally suffer on high SCC farms and there is less concern for production of safe, high quality milk and more concern for "trying to stay legal". The fact that we are willing to accept such a high prevalence of intramammary infections and a SCC of 750,000 cells/ml raises questions regarding the production of milk from healthy cows. Are we really trying to produce the best possible milk for all the consumers.
Higher SCC are related to increased risk of antibiotics in milk. Saville et al. (15) have recently analyzed data from 8,436 farms, in 9 different states for the relationship between bulk milk SCC and the risk of residue violations. The adjusted odds ratio was 1.0, 2.21, and 4.73 for SCC of <400,000, 400,000 - 750,000, and 750,000 cells/ml, respectively. Somatic cell count was clearly associated with the risk of antibiotic residues in milk and 60% of the violations were in milk with SCC of 400,000 cells/ml or greater. Similar relationships have been observed in Germany (7) and Canada (9).
The relationship between bulk tank SCC and percent quarters infected would suggest a reduced probability of finding potential human pathogens in low SCC milk. Such pathogens include: Staphylococcus aureus, Escherichia coli, Campylobacter jejuni, Yersinia enterocolitica, Listeria monocytogenes, Salmonella spp. and Clostridia spp. (2). Many of these pathogens are known to cause intramammary infection and would be expected to enter milk at greater frequency as the percent quarters infected in a herd increased. The other mechanism of entry of these pathogens into the milk supply would be as a result of contamination from milking equipment, dirty pipe lines and bulk tanks or poorly cleaned teats prior to milking. The latter would be more likely to occur in poorly managed herds compared to better managed herds with low SCC. Data to support the relationship between bulk milk SCC and the presence of potential human pathogens is currently not available but such studies are underway.
Why Not Lower the Legal Limit for SCC to 400,000 cells/ml in the US
Standards for producing milk in the U.S. are established by the National Conference of Interstate Milk Shippers (NCIMS) and approved by the Food and Drug Administration. These standards are contained in the Pasteurized Milk Ordinance (PMO). State regulators from state health departments or state departments of agriculture are the critical voting force to determine what is accepted into the PMO. Currently, NCIMS is opposed to lowering the legal limit for somatic cell count and some state regulators have commented that it was probably a mistake to have lowered the upper limit from 1,000,000 cells/ml to 750,000 cells/ml. Opposition is based on the fact that SCC are, in themselves, not a risk to human health and there is reluctance on the part of the state regulators to have to enforce a new and lower SCC limit, should the limit be reduced to 400,000 cells/ml. Again, we would agree that somatic cells are not a risk but SCC is a measure that does reflect health issues as well as quality issues. Arguments that the risk of antibiotic residues are directly related to SCC are countered by the comment that all milk tankers are tested for the presence of -lactam antibiotics before permission is given to unload at the processing plant. The critical control point is judged to be the testing of tankers, not reducing the amount of antibiotics used at the farm or keeping them out of the milk supply at the farm level. The NCIMS argument also does not take into account that tankers are not tested for all of the drugs, legal or illegal, that are used on dairy farms.
The possible relationship between higher SCC and the presence of human pathogens in milk is likewise dismissed by NCIMS because all milk is pasteurized, all pathogens are killed, and pathogen load in raw milk is apparently not a major risk to human health. Not all of the milk consumed in the US is pasteurized, as many producers and their families drink raw milk and run the risk of health consequences such as reported in the November 1997 issue of U.S. News & World Report (17). In this report, several members of a Vermont dairy farm family became seriously ill following the consumption of the raw milk produced on their farm. The pathogen responsible was Salmonella typhimurium DT 104. Of particular concern is that DT 104 is resistant to most if not all of the known antibiotics and prior to this outbreak DT 104 had not been reported in the US. The issue of Mycobacterium paratuberculosis and its ability to possibly survive pasteurization has not been completely resolved (10). The Europeans tend to view the relationship between SCC and the potential presence of human pathogens much more seriously because of the large number of raw milk products in the market place (20).
Particularly strong opposition exists to lowering the SCC limit by state regulators, and some university personnel from the southeastern part of the U.S. Their argument is that production of milk with less than 400,000 cells/ml and particularly during the summer months, is virtually impossible given the environmental conditions in that part of the U.S. Such claims do not seem to be supported by published research. Their contention is that the heat and humidity in that part of the U.S. results in severe stress to the cows causing damage or suppression to the immune system and a marked depression in milk production. In addition, the environmental conditions increase exposure to pathogens and all of these factors result in greater numbers of infected quarters and higher SCC. Clearly heat stress in itself does not cause an elevation in SCC in uninfected quarters (4). We would suggest that environmental conditions so extreme as to prevent the production of herd milk with an SCC of less than 400,000 cells/ml raises animal welfare issues. Do dairy cows really belong in such adverse environmental conditions? Is housing adequate to keep the cows clean, cool, dry, and comfortable? These basic principles of clean, cool, dry, and comfortable have been repeatedly stated by many within NMC. Producers in other parts of the U.S. also face adverse climatic conditions such as sub-zero temperatures in northern climates and excessive heat in the southwestern part of the U.S. These producers are forced to provide adequate housing to protect cows from such potentially disastrous conditions if they wish to produce high quality milk. Would not the same principles apply to the dairy industry in the southeast?
We believe that lowering the SCC limit to 400,000 is justified based on: 1) reduced risk of residues and potential pathogens and their toxic products in the milk supply; 2) harmonization of standards for international trade of milk and milk products; 3) improved consumer perception of safety and wholesomeness; and 4) the technology is readily available to all dairy producers to produce milk at less than 400,000 cells/ml. 1996 data from the National Animal Health Monitoring Service would indicate that 84.4% of U.S. producers are already producing milk with SCC less than 400,000 cells/ml and only a small percentage of producers would be required to make major changes to achieve the lower SCC level. Those producers requiring major change are likely producing an inferior product that is diluting the superior product produced by the type of dairyman we want to remain in business. Given the current attitude of NCIMS, the U.S. dairy industry may end up with a two tiered system where milk intended for international trade would be required to have an SCC of less than 400,000 cells/ml while milk intended for domestic consumption would have a substantially higher limit, or no limit. In this situation, the good milk would be for international trade and the bad milk for drinking at home. I question whether the American consumer would accept this situation.
What Is the Role For NMC?
NMC is viewed around the world as a valuable resource for information on mastitis control in dairy herds and the production of quality milk. The issues of milk safety and quality as influenced by mastitis are currently very important to all aspects of the dairy industry and will likely grow as the U.S. involvement in world trade grows. Where does the NMC stand on the issue of standards for milk and particularly the issue of SCC limits? We clearly believe that NMC should assume a leadership role in this regard and be prepared to justify the position to regulatory agencies such as USDA, FDA, and to NCIMS. The time has arrived for NMC to move beyond preparing lists of teat dips and to begin to address major issues of genuine concern to the dairy industry. NMC is an important and appropriate forum in which to debate such issues and we are confident that regulatory agencies and the dairy industry would welcome NMC’s leadership role. Let the debate begin!
References
1. Christiansen, F.A. 1997. Market aspects of the new international trade system. Bulletin of the International Dairy Federation No.325/1997, pp 4.
2. Cullor, J.S. 1997. Mastitis and dairy environment pathogens of public health concern. Proc. Natl. Mastitis Council Annu. Meet., pp 20.
3. Eberhart, R.J., L.J. Hutchinson, and S.B. Spencer. 1982. Relationships of bulk tank somatic cell counts to prevalence of intramammary infection and to indices of herd production. J. Food Prot. 45:1125.
4. Harmon, R.J. 1994. Physiology of mastitis and factors affecting somatic cell counts. J. Dairy Sci. 77:2103.
5. Heeschen, W.H. 1996. Mastitis: The disease under aspects of milk quality and hygiene. Mastitis Newsletter, Newsletters of the IDF No.144, pp 16.
6. Heeschen, W.H. 1997. Codex regulations and food safety. Bulletin of the International Dairy Federation No.319/1997, pp 24.
7. Heeschen, W.H., J. Reichmuth and G. Suhren. 1997. Quality milk production - Potential hazards, critical control points and the application of risk analysis. Proc. Natl. Mastitis Council Annu. Meet., pp 4.
8. Kimbrell, E. 1996. Codex standards in the context of SPS and TBT - What may happen in practice. Bulletin of the International Dairy Federation No.310/1996, pp 13.
9. Leslie, K.E., M.A. Godkin, Y.H. Schukken, and J.M. Sargeant. 1996. Milk quality and mastitis control in Canada: progress and outlook. Proc. Natl. Mastitis Council Annu. Meet., pp 19.
10. Mechor, G.D. 1997. Milk as a risk factor for crohn’s disease. Proc. Natl. Mastitis Council Annu. Meet., pp 50.
11. Mikkelsen, P. 1997. Trends in demand in the major regions - Latin America. Bulletin of the International Dairy Federation No.325/1997, pp 12.
12. Oterholm, A. 1996. The Codex context - Opening remarks. Bulletin of the International Dairy Federation No.310/1996, pp 7.
13. Phillips, C. 1997. Trends in demand in the major regions - South East Asia and the Far East. Bulletin of the International Dairy Federation No.325/1997, pp 31.
14. Sadinski, S. and A. MacDonald. 1997. Bulletin of the International Dairy Federation No.325/1997, pp 65.
15. Saville, W.J.A., T.E. Wittum, and K.L. Smith. 1997. Risk factors for antibiotic residues in milk. Unpublished observations.
16. Smith, K.L. 1996. Standards for somatic cells in milk: Physiological and regulatory. Mastitis Newsletter, Newsletters of the IDF No.144, pp 7.
17. Spake, A. 1997. O is for Outbreak. U.S.News & World Report, Nov. 24, Vol 123, No 20, pp 70.
18. Stanton, G. 1996. Codex standards in the context of SPS and TBT - How it may be expected to work. Bulletin of the International Dairy Federation No.310/1996, pp 8.
19. Zecconi, A. 1996. Somatic cells and their significance for milk processing (technology). Mastitis Newsletter, Newsletters of the IDF No.144, pp 11.
20. Zecconi, A. 1997. Raw milk cheese and human health concerns. Proc. Natl. Mastitis Council Annu. Meet., pp 42.