Milk Quality, Milk Production and Residue Risk

Thomas C. Hemling1, Sergio Minini2

1 DeLaval Manufacturing Inc, Kansas City, MO, USA; 2DeLaval, Olivos, Buenos Aires, Argentina

Milk is an important dietary source of protein and fat and is considered natural, wholesome, and nutritious. Consumers expect milk and other foods to be free of harmful substances, and in many cases, anticipate that food has no residues. Given the number of steps involved in milk extraction, transport and processing it is reasonable to assume there is a risk of small quantities of drugs, detergents, sanitizers or disinfectants being present in retail dairy products. Local regulatory authorities establish residue limits for these materials based on known safe or toxic limits and information about the use pattern of these materials. Historically the dairy industry has focused especially on antibiotic residues in milk, with extensive testing done on milk picked up from the farm and tests are available for on-farm use to detect bulk tank drug residues. Detergent or sanitizer residue risks have been traditionally addressed via the product registration process with little or no surveillance of residues in milk.

With milk and dairy products increasingly being traded internationally, residue levels of detergents and sanitizers are increasingly an issue. Some importers are establishing zero tolerances for materials that are allowed at higher residue levels in the country of origin. The new limits are often at the analytical detection limit, and are not related to safety risk assessments. Additionally, limitations are not focused exclusively on active substances but also on excipients. In the past two years we have seen the implementation of zero tolerance policies for material including quaternary ammonium compounds (QAC) and nonylphenol ethoxylates (NPE). As these restrictions are implemented by milk processors or importers and not national authorities, there is no motivation for the national regulatory authorities in the country of origin to rapidly approve alternative products or modified formulations. The dairy industry therefore may be left with a reduced number of tools to maintain animal health and milk quality, if alternatives are not already available on the market. In this paper we will review the major product categories that potentially result in a milk residue risk, the typical chemistries involved, and the options available to reduce or avoid residue concerns.

Antibiotic Mastitis Treatments

Global consumption of antimicrobials in food animal production was estimated at 63.15 (±1,560) tons in 2010 and projected to rise by 67 % by 2030 (Van Boeckel, 2015). Intramammary antibiotics are used during lactation and at dry off to treat mastitis. Most or all milk producing countries have a system of testing milk residues and keeping antibiotic contaminated milk out of human consumption. The frequency of milk with detectable antibiotics in most Latin American countries is low, for example in Brazil in average less than 2 % confirmed tests (Table 1) and less than 0.2 % in average in Argentina (Figure 1), indicating a broad knowledge and understanding of the issue and effective testing and enforcement programs. Antibiotic use in dairy animals remains a concern because of the potential for antibiotic resistance, especially in the case when the same antibiotic is used in human health and food production animals (CAC,

2015). Prophylactic use of dry cow antibiotics is especially under pressure (Oliver, 2011). Recent studies have shown that antibiotic use can be significantly reduced without a significant impact on therapeutic outcomes (Van Werven, 2014). Pressure to reduce antibiotic use in production animals and dairy animals specifically will continue, but the concern is more focused on resistance and human health consequence, than specifically residues in milk. With increased restrictions on antibiotic use, continued improvement in implementation of mastitis prevention practices will increase in importance.

Table 1. Results of screening and confirmation testing for antimicrobials. UHT and powder milk. 2006-2007.

UHT Milk Powder Milk

Molecule Not detected Detected Not detected Detected

B-lactamics 464 3 (0,65%) 137 3 (2,14%)Tetraciclines 456 8 (1,72%) 117 22 (15,83%)Cloranfenicol 445 19 (4,09%) 96 43 (30,94%)Neomicine 448 12 (2,61%) 133 6 (4,32%)

Streptomicine 447 17 (3,66%) 134 5 (3,60%)

Eritromicine 465 0 (0%) 138 0 (0%)

Source: Modified from Anvisa, 2009 – BRAZIL -

Graph 1. Liters (% on total liters received by Industry) rejected with inhibitors 2015 (Source: Minagri, 2015 –ARGENTINA-).

Post Milking Teat Disinfectants

Teat disinfection has been widely used across the globe for 30 to 40 years as a tool to aid in the prevention of mastitis on dairy farms (Johns, 1966). The use of post milking teat disinfectants is included as a key component in local and global programs for mastitis management: 5 Point Plan, 12 Golden Rules, Countdown Downunder, SAMM Plan to name a few.

5 Point Plan1. Disinfect all teats after every milking2. Treat all cases of mastitis promptly and record data3. Use dry cow treatment on all cows4. Cull all cows with 3 or more cases5. Maintain milking machine properly

Post milking teat disinfection programs were implemented initially to control contagious mastitis at a time when Staphylococcus aureus and Streptococcus agalactiae were major causes of mastitis. At that time BTSCC levels were often in excess of 500.000 cells/ml, and mastitis infection rates were in the order of 150 % per year. Through implementation of mastitis control programs we now see SCC averages in many countries at or below 200.000 cells/ml, along with dramatic reductions in infections rates to as low as 2-3 % per month (Riekernik, 2008). Also

because the control programs successfully address contagious mastitis, we now see environmental mastitis pathogens predominant in many herds. Studies suggest that in South America we still see higher prevalence of contagious pathogens (Dieser, 2013; Gianneechini, 2014).

Since the initial implementation of posting milking teat disinfection, the dairy industry has been constantly evolving. There has been:

1) A substantial growth in farm size; 2) An increase in daily milk production per cow;3) An increase in prevalence of confinement dairies; 4) Pressure by milk processors and authorities to reduce the use of antibiotic to treat mastitis during lactation;5) Bans on prophylactic use of antibiotics during the dry period; 6) Wide implementation of robotic milking; and 7) Increased availability of on-farm diagnostics to provide point of use information on mastitis and other animal health parameters.

Most recently as a result of the elimination of quota in Europe and other market factors, more milk is entering international trade. As a consequence, authorities, dairies and consumers are placing increased pressure on milk producers to reduce milk residues stemming from teat disinfection, antibiotic treatment, or even equipment cleaning chemicals.

Sustainable Options

For the past 30 years numerous active substances have been considered, tested and marketed as teat disinfectants. Iodine is the most widely studied germicide for both pre- and post- milking teat disinfection, with over 30 clinical studies reported in the NMC bibliography, and commercial market shares ranging from 55 to 95 %. Other germicides tested and marketed include hydrogen peroxide, lactic acid, sodium hypochlorite, chlorhexidine, chlorine dioxide, dodecylbenzene sulfonic acid, various alcohols, and in some instances combinations of these materials. Iodine has been shown to be especially effective, particularly in formulations with elevated free iodine (Foret, 2005). With ever increasing concern over antimicrobials or biocide residues in milk the choice of suitable actives substances is becoming more restricted. It is likely that market demands will limit the antimicrobial substance to those naturally present in food or specifically in milk. Of all the materials listed, iodine, hydrogen peroxide and lactic/organic acids would be preferred over synthetic materials such as chlorhexidine or dodecylbenzene sulfonic acid (DDBSA).

Iodine is an essential animal and human nutrient and converts to the non-germicidal iodide when contacted with milk (Flachowsky, 2013). The potential residue effect of iodine teat disinfection is well studied and is summarized by Hemling (2000). Hydrogen peroxide likewise decomposes to oxygen and water. Lactic acid is naturally present in milk and residue contribution from teat disinfection is not detectable versus the natural lactic acid milk concentration variation. In

contrast, use of chlorinating materials such as sodium hypochlorite, sodium dichloroisocyanurate or tosylchloramide will likely be restricted because of risk of formation of the carcinogen chloroform (Siobham, 2012), and because of issues with skin safety.

Recently, products containing copper or silver have been investigated in topical disinfectant products including teat disinfectants (Figueroa, 2013). While data is not yet available on milk residues, these materials do not biodegrade and potentially bio-accumulate in dairy cows or consumers of milk. Essential oils and other natural sounding materials typically have a limited breadth of antimicrobial activity and while being safe as a residue in milk, are likely to impart an unwanted flavor or odor.

Table 2. Teat Disinfectant Germicides and Sustainability.

Germicide Market Share

Natural in milk

% in Teat dip Ready To Use

Other Germicide as Residue in Milk

Iodine 55-85% Yes 0.1 – 1% NPE? No – converts to iodide

Hydrogen Peroxide

0-10% Yes 0.5 – 1% No - decomposes

Chlorine Dioxide 2-12% No 0.5 Chlorite; 100-200 ppm Chlorine Dioxide

Chlorite residue,

No - decomposes

Chlorine (bleach) 2-20% No 0.05 to 2% THM - chloroform

No - decomposes

Lactic-Organic Acid

3-12% Yes 2 to 6% not germicidal at milk pH

Chlorhexidine 3-10% No 0.3 to 0.5% Yes

DDBSA 2-4% No 2 to 4% Low pH normally required?

NPE: Nonylphenol etoxilates; THM: trihalomethanes; DDBSA: dodecylbenzene sulfonic acid(Source: Hemling, 2015)

Product type and application methods also may impact the residue risk. A study at Cornell University shows small differences based on product form, iodine concentration and application method. The study included low viscosity-sprayable products, and a high viscosity barrier

product used for control or environmental mastitis. All disinfectants tested showed a low impact on milk iodine levels.

Table 3. Milk Iodine Residue from disinfection products applied as post milking disinfectant

Product % Iodine Application Iodine in milk (ppb)

From Teat dip (ppb)

Prima Hydrogen Peroxide

dip 148

Trifender 0.25 dip 157 9

Trifender 0.25 spray 178 30

Iodofence 0.25 Barrier – dip 163 14

Bovidip 0.50 dip 177 29

(Source: French et al in 2014)

Automated application methods are gaining acceptance in many markets and raise additional concerns about residue risk. Teat disinfectants can be applied by sprays systems that are part of Automated Milking Systems (AMS), stand alone teat spray robots or by auto-injection from inside the liner as it is detached from the teat. Researchers and regulatory authorities will need to be careful to understand whether an increased residue risk is coming from a particular teat disinfectant product or teat disinfectant application device.

Excipients in the teat dip include skin conditioning additives, thickeners, buffers, surfactants, and dyes. These materials are normally not a residue concern and usually have some degree of food contact approval. The surfactant NPE (and related compounds), commonly used in iodine teat disinfectants, has been recently banned as residue in milk or dairy products imported into China. The limit is 10 ppb, the analytical detection limit. The NPE is of concern because it can act as an endocrine disruptor (Osimitz, 2105). Alternatives to NPE are available and have been used by some teat dip manufacturing companies for over 30 years.

Pre-milking Teat Disinfectants and Cleaners

Pre-milking treatments are used to remove soils and to remove or kill bacteria present on the teat prior to milking. The same germicides used in post milking teat disinfectants have been used also in pre-milking teat disinfectants but typically at lower concentrations. The lower concentration is used because of the risk of milk residue, if the pre-milking disinfectant is not thoroughly wiped off the teat. Iodine at 0.1 % to 0.25 % is the most commonly registered product for pre-milking while 0.5 to 1.0 % is most common for post-milking disinfection. Published data shows acceptable milk iodine residue levels for 0.1 to 0.25 % products (Hemling, 2000). As with post-milking disinfection, active substances that are naturally present in milk would be preferred over synthetic substances or metals that may bio-accumulate.

In many European countries pre-milking products have been marketed as cleaners even if they contain substances with known disinfecting properties. Teat cleaners have been historically exempt from registration so products containing lactic acid, alcohol or hydrogen peroxide have been marketed without disinfecting claims. With the ongoing increase in average herd size the infection pressure from environmental pathogens also increased. When this is coupled with restrictions on the use of blanket dry cow therapy, the need for a tool to manage environmental infections is increased. Use of pre-milking teat disinfectants with low residue risk germicides such as lactic acid, hydrogen peroxide, and low level iodine is expected to increase. These are naturally present in milk and convert to non-germicidal forms once in contact with milk.

Udder soaps, udder washes and pre-wetting udder towels have been used as teat cleaning treatments. These products have often included an antimicrobial substance as a “preservative” or as a “towel disinfectant”. Commonly used materials include QACs, chlorhexidine and polyhexamethylene biguanide (PHMB) all of which are synthetic, poorly degrade, potentially bio-accumulate, and remain germicidal in milk. These active substances will likely be banned from this application by regulatory authorities or by international trade restrictions.

Milking System Detergents and Sanitizers

Detergents and sanitizers used to clean milk contact surfaces of milking machine are another potential source of milk residue. The cleaning process in most countries includes a pre-rinse, a hot cleaning step (or combination cleaning-sanitizing step) followed by a post rinse or a final sanitizing step. In some markets, authorities allow a final sanitizing with a “non-rinse” sanitizer. This is allowed if the materials in the sanitizer are approved for direct or indirect food contact. Depending on water hardness, the cleaning process may employ an acid product to remove minerals. This is done either within the process (US method), by use of an acid-sanitizer (US alternative method) or in an alternating method (EU method).

Table 4. Standard cleaning-sanitizing Processes

US US Alternative US Acid EU (alkali dominant or alternate*)

Pre-rinse Pre-rinse Pre-rinse Pre-rinse Pre-rinseHot chlor-alkaline

Hot chlor-alkaline

Hot Acid Hot chlor-alkali Hot Acid

Acid rinse Acid sanitizer Sanitize Post Rins3 Post RinseSanitize*Frequency of acid cleaning is dependent on water hardness.

Removal of milk soils is achieved via rinsing and cleaning with a hot chlorinated-alkaline detergent or hot acid. The use of chlorine (sodium hypochlorite) can result in formation of the trihalomethanes (THM) chloroform. Under normal conditions the risk of milk residue is extremely low. Investigation suggest that chloroform in milk more likely results from the use of a final step chlorine sanitization with a poorly draining system or from use of elevated concentrations of hypochlorite (O’Brien, 2009; Siobhan, 2012;). In powdered or tableted

chlorinated detergents or sanitizers sodium dichloroisocyanurate is the source of hypochlorite. This material also potentially leaves an isocyanurate/cyanuric acid residue. Isocyanurate (like melamine) has a high weight percent of nitrogen, and some milk processors test for isocyanurate as a substance introduced intentionally in milk to increase protein test results. Also melamine can degrade to cyanuric acid, so cyanuric acid residue resulting from use of dichloroisocyanurate may be assumed to be derived from melamine addition (Braekevelt, et al., 2011; Sun, 2011).

Acid detergents are typically blends of mineral or organic acids with surfactants. These are normally easily rinsed from the cleaning system and do not result in any special residue concern.

Sanitizers and antimicrobial materials are often used in the final step of the cleaning process and in some countries are approved for use without a final rinse. Residue concerns should be minimal when properly used according to label direction in well draining installations. Well accepted sanitizers include hypochlorite (see precaution above), peracetic acid and fatty acid sanitizers. Recently, concern has been raised about the use of QACs as sanitizers in cleaning products. QACs are substantive to surfaces and remain antimicrobial in milk. Certain importing countries like China have established a zero tolerance and have banned QACs in imported dairy products down to the detection limit of 20 ppb. Other cationic substances such as chlorhexidine, PHMB, or Bis 3-aminopropyl dodecylamine would have similar concerns.

References

AGENCIA NACIONAL DE VIGILÂNCIA SANITÁRIA – ANVISA, Brazil 2009. Programa de Análise de Resíduos de Medicamentos Veterinários em Alimentos de Origem Animal (PAMVet). Relatório 2006/2007. Monitoramento de Resíduos em Leite Exposto ao Consumo. Brasilia.

Braekevelt, E., Lau, B. Y., Feng, S., Ménard, C., & Tittlemier, S. A. 2011. Determination of melamine, ammeline, ammelide and cyanuric acid in infant formula purchased in Canada by liquid chromatography-tandem mass spectrometry. Food Additives and Contaminants, 28(6), 698-704.

CODEX ALIMENTARIUS COMISSION, CAC. July 2015. MAXIMUM RESIDUE LIMITS (MRLs) AND RISK MANAGEMENT RECOMMENDATIONS (RMRs) FOR RESIDUES OF VETERINARY DRUGS IN FOODS, CAC/MRL 2-2015

Dieser, S. A., Vissio, C., Lasagno, M. C., Bogni, C. I., Larriestra, A. J., & Odierno, L. M. 2014. Prevalence of pathogens causing subclinical mastitis in Argentinean dairy herds. Pakistan Veterinary Journal, 34(1), 124-126.

Figueroa, G. 2013 “Utilización de formulaciones en base a cobre para el control de mastitis en ganado bovino” Informe proyecto FIA CHILE FYT-2013-0030.

Flachowsky, G., Franke, K., Meyer, U., Leiterer, M., & Schöne, F. 2014. Influencing factors on iodine content of cow milk. European journal of nutrition, 53(2), 351-365.

French, E, Henderson, M, Zurakowski, M, Motoko M, Schukken Y, Hemling, T 2014. IODINE TEAT DISINFECTANTS MINIMALLY INCREASE MILK IODINE COMPARED TO NON-IODINE TEAT DISINFECTANTS, National Mastitis Council 53rd Annual Meeting p249-250

Foret, C. J., Corbellini, C., Young, S., & Janowicz, P. 2005. Efficacy of two iodine teat dips based on reduction of naturally occurring new intramammary infections. Journal of dairy science, 88(1), 426-432.

Gianneechini, R., Concha, C., Delucci, I., Gil, J., Salvarrey, L., & Rivero, R. 2014. Bovine mastitis, distribution of pathogens and antimicrobial resistance in the Southern Dairy Basin of Uruguay. Veterinaria (Montevideo), 50(196), 4-32.

Hemling, Thomas C. 2000. “Iodine Residues in Milk,” XXI World Buiatrics Congress, Punta del Este, Uruguay, December 4-8, 2000

Hemling, Thomas C. 2015. “Sustainable Teat Disinfection for the Prevention of Mastitis” XVIII International Conference for Veterinarians, Polinica, Poland

Johns, C. K. 1966. Use of sanitizers in preventing intramammary infections. J. Milk Food Technol. 29:309.

Ministerio de Agricultura, Ganaderia y Pesca – MINAGRI, Argentina. 2015. Website de la Subsecretaría de Lechería - Sistema de Pago por Calidad: http://www.minagri.gob.ar/site/_subsecretaria_de_lecheria/lecheria/04=Pago_por_Calidad/07_Estadisticas/index.php

O’Brien. B. 2009. Reducing Chemical Residue in Milk Trichloromethane-TCM. Moorepark Dairy Production Research Center: Milk Quality Workshop, December 2009.

Riekerink, R. O., Barkema, H. W., Kelton, D. F., & Scholl, D. T. 2008. Incidence rate of clinical mastitis on Canadian dairy farms. Journal of Dairy Science, 91(4), 1366-1377

Oliver, S. P., Murinda, S. E., & Jayarao, B. M. 2011. Impact of antibiotic use in adult dairy cows on antimicrobial resistance of veterinary and human pathogens: a comprehensive review. Foodborne pathogens and disease, 8(3), 337-355

Osimitz, T. G., Droege, W., & Driver, J. H. (2015). Human Risk Assessment for Nonylphenol. Human and Ecological Risk Assessment: An International Journal, (ahead-of-print), 1-17

Siobhan, R., David, G., Kieran, J., Ambrose, F., & BERNADETTE, O. B. (2012). Evaluation of trichloromethane formation from chlorine‐based cleaning and disinfection agents in cow’s milk. International journal of dairy technology, 65(4), 498-502.

Sun, P., Wang, J. Q., Shen, J. S., & Wei, H. Y. (2011). Residues of melamine and cyanuric acid in milk and tissues of dairy cows fed different doses of melamine. Journal of dairy science, 94(7), 3575-3582. Van Boeckel et al, 2015 “Global trends in antimicrobial use in food animals”, PNAS Early Edition www.pnas.org/cgi/doi/10.1073/pnas.1503141112

Van Werven, T. 2014. “The use of Antimicrobials in Prevention and Cure of Mastitis: What is Our Responsibility” NMC Regional Meeting Gent, Belgium.