New Raw Milk Research From the 2023 IMGC Symposium

A Farmer’s Takeaways from the 2023 Symposium of the International Milk Genomics Consortium (IMGC)

“If you are the smartest person in the room, you are in the wrong room.”

Introduction

Well…I was in the right room at IMGC with a huge opportunity to learn and grow. Just like all prior years.

The 20th International Milk Genomics Consortium (IMGC) Symposium was held on September 6-8 2023. This was the 12th year that I have attended the IMGC Symposium. For the last several years, the Raw Milk Institute has been an official Bronze Level Sponsor of the conference. These conferences have taken me all over the world, including Cork Ireland, Quebec Canada, Aarhus Demark (twice), Sydney Australia, and UC Davis in California several times. I am nearly always the only farmer in the room filled with dairy processing scientists, PhD students, dairy science professors and university professors, and other milk researchers.

Over 12 years, I have made some great friends and created some important collaborations and alliances. I am approached by PhDs, especially after I speak at the microphone after a particularly engaging presentation that begs questions. They say things like, “Keep on asking those great questions!”  I am the only one that can ask those questions because everyone else would potentially lose their NIH or industry grants if they dared to asked those kinds of questions.

Time and interest are ushering in a new generation of open-minded PhD researchers, many of whom are women. They all want to talk about raw milk and its bioactive elements. Raw milk is truly a miracle of nature.  Being an event sponsor has allowed greater access to insider information about all things milk.  Below are my main takeaways from three intensive days of meetings, interactions, meals and dinner parties, and presentations in Cork Ireland at the University of Cork.

Raw Milk Institute was a Bronze Level Sponsor of the 2023 IMGC Symposium

Raw Milk Nourishes, Protects, and Directs

Raw milk is incredibly complex and perfectly designed to nourish, protect, and direct. We all know that raw milk is designed as the first food of life for babies to thrive and grow, yet as researchers continue to study raw milk, they discover many more benefits.

For instance, raw milk serves as a delivery system for immune-bioactive proteins. Peptides (which are chains of amino acid proteins) are protective of the baby by not allowing pathogens to cause illness. These functional proteins serve many roles, including protection of the baby.

Other specialized-proteins in breastmilk include natural mRNA, which provide the genetic information to direct cellular metabolic processes in the baby.  Breastmilk also contains stem cells for repair of damaged cells or tissues.

Raw milk also contains everything needed for its digestion. Raw milk has proteases, peptidases (for digesting proteins), lipases (for digesting fats), and bacteria that make lactase (for digesting lactose).

Additionally, when people drink milk, over time there are changes in the composition of the gut bacteria that make milk digestion easier. Lactase-producing bacteria found in the gut become the probiotic and as they feed on lactose, that becomes their selected prebiotic (food that bacteria chose to digest or eat). Over time the populations of these lactose-loving probiotic bacteria increase when they are fed lactose from dairy products.

The various milk proteins, immunoglobins, enzymes, fats and sugars are “qualitatively similar” between human breastmilk and cow milk. However, they are “quantitatively different” and appear at different levels and amounts in cow milk versus human milk. The same would be true for other bovine milks. The similarities are why humans can drink raw milk from cows, goats, and other animals. 

Milk’s Benefits Can’t Be Extracted

Many raw milk researchers are focused on finding ways to extract beneficial elements from raw milk. However, these elements are designed to work together with the full complement of many different macro- and micro- nutrients, enzymes, probiotics, etc in whole raw milk.

New products made with bio-actives extracted from raw milk will likely be met with suspicion, as well they should. The health benefits from whole, raw milk are the result of a complex interplay of bio-actives. Outside of the whole food matrix, those bio-actives are incomplete and not as effective as in their natural state.

Milk Fat is Essential to Its Beneficial Properties

Butterfat in milk is an essential part of milk’s overall beneficial properties. This fat is known to benefit brain development, immune system development, intestinal development, and the composition of the gut microbiota.

Butter fat globules are three-layer thick capsules that come in different sizes. The three-layered capsules are used by the gut as fiber; they also provide butyrate and butyric acids which are highly beneficial and healing to the lower gut. 60% of the bioactive elements found in raw milk are “carried on or inside” the fat globule. This says so much about skim milk, which has lost much of its beneficial value with the removal of the fat.

Researchers discovered that the fat globules in the milk are smaller in cows fed a high energy diet with high stress levels, such as cows being kept in concentrated animal feeding operations (CAFOs). The smaller fat globules in the milk do not contain bacteria inside that could ride through the stomach to the lower gut.

In contrast, the fat globules are larger in cows fed a low energy diet and under low stress levels (such as cows in pasture-based operations).  These larger fat globules carry bacteria inside of them. It is thought that the fat cell may act as a protective carrier vessel to carry bacteria though the stomach acid environment into the lower gut where they may be beneficial.

Pasteurization Damages and Denatures Milk

Pasteurization damages milk such that it becomes oxidated, highly allergenic, and hard to digest. It is a common protocol to pasteurize milk up to 3 or 4 times to achieve longer shelf life and assure that the milk is completely dead, with no regard for the essential and beneficial bio-actives that are destroyed in the process. 

Raw milk contains everything it needs to digest itself. Raw milk contains enzymes and bacteria that help create more enzymes to digest raw milk and all the sub elements. Milk maldigestion has been over simplified. It is not just lactose; it is the proteins and fats that also need help with digestion.

After pasteurization the bioactive elements needed for milk to digest itself are missing! Fats, proteins, and sugars all need digesting, but their enzymes and digestive bacteria are denatured or dead.  Without active enzymes, digestion of fat (via lipase) and proteins (via protease) is inhibited. This results in maldigestion in some consumers. 

Whereas raw milk helps to build immune system strength, pasteurized milk does not build up the immune system. Heat denatures the functional proteins and does not allow cellular direction. This can result in cellular confusion and chaos.

Raw whey proteins are highly anti-inflammatory and have many health benefits. The raw whey health benefit findings are consistent with other researchers in the Netherlands, including Dr. Ton Baars’ research on whey proteins showing that they stabilize MAST cells, control histamine release, and reduce allergies.

However, all whey is required to be pasteurized in the USA as per the Food and Drug Administration (FDA) and Pasteurized Milk Ordinance. Whey proteins are destroyed by processing and are highly sensitive to heat. One researcher has been frustrated in trying to extract the beneficial components from pasteurized whey. The heating of whey makes the components “sticky” such that they plug up the ultrafiltration micropores. Therefore, ultra filtration cannot be used to extract whey components from pasteurized whey.

New Pasteurization Technologies Cause Less Damage Than Traditional Heat Pasteurization

As an alternative to heat-based pasteurization, researchers are studying other methods such as high pressure (HPP), ultrafiltration, and ultraviolet (UV) light. These methods are effective at inactivating bacteria and less harmful to milk than heat-based pasteurization. For instance, both high pressure processing and ultraviolet processing preserve some of the bioactive milk proteins better than heat-based pasteurization.

Nonetheless, milk processors in the USA are resisting the use of these new technologies. In some other countries, UV and HPP are being successfully used, but in the USA the FDA continues to represent processors’ interests and thereby block the ability to innovate with these alternatives to heat processing. This failure to innovate with HPP, UV or Ultrafiltration is creating a loss of consumer interest in pasteurized milk as people continue to suffer from maldigestion when consuming pasteurized milk.

In Studies, 20,000+ Kids Drank Raw Milk With NO Milk-Related Illnesses

The pioneering PARSIFAL and GABRIELA studies of more than 55,000 kids in Europe really set the international high bar for studies on raw milk. The overall findings included reduced rates of asthma, eczema, respiratory illnesses, fevers, allergies, and ear infections in children who drank raw milk.

At the symposium, it was emphasized that during all of those studies and over twenty years of research, there was never a “red flag event.” A red flag event would be a reported illness from raw milk consumption. The studies included data from more than 20,000 children who drank raw milk, and there was not a single red flag event!

Yet, at the end of each of the peer reviewed and journal published articles, there is a disclaimer that says something such as, “even though there are health benefits to consuming raw milk, the researchers can not recommend raw milk because of the risks of raw milk consumption.” This disclaimer was included because peer review and journal publication political pressures demanded it, despite the fact that there was no basis in the research data.

Dr. Markus Ege MD and Mark McAfee, in Cork Ireland at the IMGC symposium 2023

Raw Milk Provides Sustainability for Farmers and Superb Nutrition for Consumers

Farmers have been denied fair markets for their dairy products for more than a century. All of the value-added efforts are happening after products leave the farm. Milk processors continue to ensure that farmers are paid low prices for their milk, resulting in the loss of thousands of family farms. However, raw milk provides a pathway to sustainability and life satisfaction for dairy farmers.

Raw milk presents a unique farmstead product that brings all the added value back to the farmer with an incentive to work on quality. By selling directly to consumers, raw milk farmers are able to obtain greater financial rewards for their work, while consumers benefit from the improved flavor and nutrition. It’s a win-win for farmers and consumers!

Raw milk that is carefully and intentionally produced for direct human consumption is a low-risk food. This type of raw milk is wholly different from raw milk being produced in unhygienic conditions. Raw milk intended for direct human consumption is produced in sanitary conditions, with much care to ensure that the animals are healthy and that the milk is clean. This type of raw milk is tested often and held to rigorous standards to ensure that it is being produced in a way that discourages pathogen growth.

By combining nature’s blueprints, the bio-actives found in whole raw milk, standards for good production practices and modern testing systems, RAWMI Listed farmers are nourishing consumers safely. Congrats to all of the RAWMI Listed pioneers! 

Texas Raw Milk Training: For World-Class, Low-Risk Raw Milk!

Raw Milk Institute (RAWMI) recently taught a full-day intensive farmer training class on Production of Low-Risk, World-Class Raw Milk in Mount Pleasant Texas. RAWMI President Mark McAfee and Vice President Sarah Smith traveled to Texas to teach this class in collaboration with Northeast Texas Community College (NTCC).

There were 25+ attendees from Texas, Louisiana, and Arkansas. Attendees included farmers who are already producing raw milk, prospective farmers considering raw milk production, and students who were interested to know more about raw milk.

RAWMI presented our full 5-hour training presentation in the NTCC Ag Complex classroom, complete with catered snacks and lunch from local businesses.

A Texas state dairy inspector also presented and answered questions about Texas raw milk laws. She provided invaluable information about Texas’ Raw for Retail statute as well as the allowance for herdshares in Texas.

Following our classroom presentation, we took the students for a farm tour at Udder Delight Dairy, which is a raw milk micro-dairy that is operated by Tom and Brenda Ramler. Their dairy is currently working through our free one-on-one mentoring process to become a RAWMI Listed dairy.

Overall, this class was a resounding success! The students were engaged and appreciative of the opportunity to learn more. Several farmers who attended the class have expressed interest in becoming RAWMI Listed as well.

RAWMI extends special thanks to Tom Ramler, Jimmy Smith, and Northeast Texas Community College for sponsoring and coordinating this important step for safe, low-risk raw milk in Texas!

Managing the Increased Risks of Calf-Sharing on Raw Milk Farms

Calf-sharing, i.e. allowing a cow’s offspring to nurse directly from its mother, is a common practice on small dairy farms.  Many farmers and consumers think that calf-sharing is ideal for the health and well-being of both the cow and calf, and it does present an idyllic picture of farm life. Calf-sharing can also reduce the workload for farmers, who don’t have to bottle-feed the calves.   

However, farmers who are producing raw milk need to be aware that calf sharing increases the risk of pathogens being present in the raw milk. The same is true for kid-sharing with goats.

Pathogens, Calves, and Kids

You may wonder: Why do calf-sharing and kid-sharing increase the risk of pathogens in raw milk?  Just like human babies, calves and kids explore the world with their mouths and can then directly transfer harmful bacteria to the udders as well as to the inside of the teat canals. Calves and kids have immature immune systems and are therefore more likely to harbor pathogens themselves.

Although pathogens in well-produced raw milk are rare, they are still an important consideration and we encourage all raw milk farmers to take pathogens seriously.  Pathogenic bacteria that can be carried by calves and kids include E coli 0157:H7, Salmonella spp., Campylobacter spp., and Listeria monocytogenes. Illnesses from these pathogens can be serious or even fatal. 

Many scientific studies have verified that calves and kids are more likely to carry pathogens than their fully-grown counterparts. Below are a couple of the studies; additional studies are listed in the references section at the end of this article.

• A longitudinal study of Shiga-toxigenic Escherichia coli (STEC) prevalence in three Australian dairy herds -

  https://www.sciencedirect.com/science/article/pii/S037811359900173X?via%3Dihub -

  "In concurrence with previous studies, it appears that cattle, and in particular 1–14-week-old weanling calves, are the primary reservoir for STEC and EHEC on the dairy farm."

• Age related differences in phylogenetic diversity, prevalence of Shiga toxins, Intimin, Hemolysin genes and select serogroups of Escherichia. coli from pastured meat goats detected in a longitudinal cohort study - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7391229/ - "Overall, virulence genes and STEC [virulent e coli] were detected in isolates from goat kids in higher proportions than adult animals. Additionally, isolates with 2 or more virulence genes were significantly higher in pre-weaned and goat kids around weaning than in adult goats."

Illness outbreaks from petting zoos provide further confirmation that calves and kids can transfer pathogens in real-world conditions.

• Animal petting zoos as sources of Shiga toxin-producing Escherichia coli, Salmonella and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae -   https://pubmed.ncbi.nlm.nih.gov/33382208/ - “Animal petting zoos and farm fairs provide the opportunity for children and adults to interact with animals, but contact with animals carries a risk of exposure to zoonotic pathogens and antimicrobial-resistant bacteria... Of 163 faecal samples, 75 contained stx1, stx2 or stx1/stx2 genes, indicating the presence of STEC. Samples included faeces from sika deer (100%), sheep (92%), goats (88%), mouflons (80%), camels (62%), llamas (50%), yaks (50%), pigs (29%) and donkeys (6%)…”

This information makes some farmers and consumers uncomfortable, yet it is still important to consider in developing a plan for minimizing the risk of pathogens from raw milk.   

Staph aureus, Calves, and Kids

In addition to pathogens that can cause human illness, calf-sharing (and kid-sharing) can increase the chance that Staph aureus will be widespread in the dairy herd.  Staph aureus is a type of bacteria that colonizes inside the mammary tissue, thereby increasing the risk of recurrent mastitis. The presence of Staph aureus can also cause scar tissue in the udder, which may result in lower milk production over time.  Cows and dams can transfer Staph aureus to suckling calves and kids, such that Staph aureus can become widespread in the dairy herd.  

Bottle-Feeding Has the Lowest Risk for Pathogens

At the Raw Milk Institute, our goal is to help farmers better-understand the potential risks in raw milk production so that they can then take steps to minimize the risks.  We are not the raw milk police, and we do not forbid anyone from calf-sharing. However, we want to make sure that farmers are aware of the risks and can then plan for how to reduce the risks.  

To achieve the lowest risk-profile, calves and kids would be bottle-fed.  It is nonetheless very important to ensure that the calves and kids receive the colostrum in order to help build up their immune systems. Be aware that the manure from calves and kids can also be a source of pathogens.  

Studies and farmer experience have shown that early separation (within 24 hours of birth) reduces the stress of the separation on both calves and cows. Leaving the cow and calf together for longer periods increases the stress related to separation.

• Effects of early separation on the dairy cow and calf: 2. Separation at 1 day and 2 weeks after birth - https://pubmed.ncbi.nlm.nih.gov/11179551/ - “Behavioural observations were conducted on 24 Holstein dairy cow-calf pairs during the first 24h after separation. Before separation, cow-calf pairs were generally inactive. After separation, cows from the late-separation treatment group showed higher rates of calling, movement and placing the head outside the pen, than cows in the early-separation group.”

Calves who have been separated from their mothers will do best if they are kept with at least one other calf rather than in isolation. 

• The effect of individual versus pair housing of dairy heifer calves during the preweaning period on measures of health, performance, and behavior up to 16 weeks of age - https://pubmed.ncbi.nlm.nih.gov/33358809/ - Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing.

Raising calves can be time-intensive, so some farms choose to instead have their calves raised offsite at farms that specialize in calf-rearing.  

Managing the Risks of Calf-Sharing

For farms that choose to calf-share or kid-share, below are some risk management strategies that have been employed successfully in small dairy farms that have participated in the Raw Milk Institute’s Listing program.  

• Apply extra diligence to udder preparation and stripping.  Ensuring that the teats are well-cleaned, pre-dipped, and stripped prior to milking will reduce the chance of pathogens being present. (See our Udder Prep for Raw Milk article for more information.)

• Closely monitor the calves/kids for any signs of illness.  If the calves/kids are ever showing signs of illness (such as diarrhea, runny nose, etc.), the milk would potentially have a greater risk of pathogens.  The milk should then be either diverted and not used for direct human consumption or the calves/kids should be separated from the herd until the illness has cleared.

• Perform regular milk culture testing of your herd for Staph aureus to make sure it is not present. Staph aureus can show up intermittently so one test does not necessarily clear the herd.

• Have a "nurse cow" or “nurse dam” to feed the calves or kids, whose milk is not used for human consumption.  This method needs to be utilized carefully, as too many calves/kids per nurse cow/dam can result in a loss of body condition and health problems for the nurse cow/dam.

• As they grow to a few months old, some calves/kids can be especially hard on the teats when nursing.  This can result in damage or injury to the teats. If this occurs, it is best to separate the offspring from their mothers.

It is also worth noting that calf-sharing (or kid-sharing) will reduce the amount of milk that is available to sell to customers. This can become especially problematic as the calves/kids reach 5+ months of age.

Choosing not to calf-share or kid-share is a good option for farmers who want to have the lowest risk of pathogens in their raw milk.  However, calf-sharing and kid-sharing can be done successfully when farmers acknowledge and manage the risks. The techniques listed above will reduce the likelihood of anything going wrong, for the benefit of both the customers and farmers.

A less-detailed version of this article was published in the June-July 2023 issue of Graze Magazine.

References

1. Age related differences in phylogenetic diversity, prevalence of Shiga toxins, Intimin, Hemolysin genes and select serogroups of Escherichia. coli from pastured meat goats detected in a longitudinal cohort study - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7391229/ - "Overall, virulence genes and STEC [virulent e coli] were detected in isolates from goat kids in higher proportions than adult animals. Additionally, isolates with 2 or more virulence genes were significantly higher in pre-weaned and goat kids around weaning than in adult goats."

2. Role of calf-adapted Escherichia coli in maintenance of antimicrobial drug resistance in dairy calves - https://pubmed.ncbi.nlm.nih.gov/14766551/ - "The prevalence of antimicrobial drug-resistant bacteria is typically highest in younger animals, and prevalence is not necessarily related to recent use of antimicrobial drugs. In dairy cattle, we hypothesize that antimicrobial drug-resistant, neonate-adapted bacteria are responsible for the observed high frequencies of resistant Escherichia coli in calves."

3. Antibiotic resistance and transferable antibiotic resistance of Escherichia coli isolated from Swedish calves 5 and 30 days old - https://pubmed.ncbi.nlm.nih.gov/1094406/ - "In comparison with the 30-day-old calves, the 5-day-old calves had significantly more strains with transferable antibiotic resistance (95.8 percent as against 63.4 percent)."

4. Enterotoxigenic Escherichia coli Infections in Newborn Calves: A Review -

   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7130746/pdf/main.pdf - "Diarrhea caused by enterotoxigenic Escherichia coli is an infectious bacterial disease of calves that occurs during the first few days of life. The Escherichia coli that cause the disease possess special attributes of virulence that allow them to colonize the small intestine and produce an enterotoxin that causes hypersecretion of fluid into the intestinal lumen. These enterotoxigenic Escherichia coli are shed into the environment by infected animals in the herd and are ingested by newborn calves soon after birth."

5. Prevalence of Escherichia coli O157:H7 in range beef calves at weaning -

   https://www.cambridge.org/core/journals/epidemiology-and-infection/article/prevalence-of-escherichia-coli-o157h7-in-range-beef-calves-at-weaning/EBD00C9EB16D36476F75D825C05139B0 - "This study was designed to determine the prevalence of Escherichia coli O157:H7 infection of beef calves at weaning, prior to arrival at the feedlot or mixing with cattle from other sources. Fifteen range cow-calf herds, which weaned calves in October and November, were sampled in Kansas, Missouri, Montana, Nebraska and South Dakota... Thirteen of the 15 herds (87%) were found to have at least one positive isolation of E. coli O157:H7 in faecal samples...This study indicates that E. coli O157:H7 infection before weaning, prior to entry into feedlots, is widespread. Furthermore, serologic evidence suggests that most calves (83%) and all herds (100%) have been exposed to E. coli O157.

6. Diversity, Frequency, and Persistence of Escherichia coli O157 Strains from Range Cattle Environments -

   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC152399/ - "The number of XbaI-PFGE subtypes, the variable frequency and persistence of subtypes, and the presence of identical subtypes in cattle feces, free-flowing water sources, and wildlife feces indicate that the complex molecular epidemiology of E. coli O157 previously described for confined cattle operations is also evident in extensively managed range cattle environments."

7. A longitudinal study of Shiga-toxigenic Escherichia coli (STEC) prevalence in three Australian dairy herds -

   https://www.sciencedirect.com/science/article/pii/S037811359900173X?via%3Dihub -

   "In concurrence with previous studies, it appears that cattle, and in particular 1–14-week-old weanling calves, are the primary reservoir for STEC and EHEC on the dairy farm."

8. Comparison of Diversities of Escherichia coli O157 Shed from a Cohort of Spring-Born Beef Calves at Pasture and in Housing - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1065151/ - "Overall, there was no demonstrable difference in shedding between calves when housed and at pasture. However, when shedding occurred, the rate of shedding was greater among calves in pen S (0.025 < P < 0.05) and pen N (0.05 < P ≤ 0.10) than when at pasture"

9. Persistence of verocytotoxin-producing Escherichia coli O157:H7 in calves kept on pasture and in calves kept indoors during the summer months in a Swedish dairy herd -

   https://pubmed.ncbi.nlm.nih.gov/11407548/ - "The objective of this part of the study presented here was to examine the persistence of VTEC O157:H7 in calves that were kept on pasture and indoors, respectively, during the summer...The faecal samples from the calves kept on pasture were negative during the whole period...This suggests that calves on pasture may be less exposed to the bacteria or that they clear themselves. In the pen group, there were between one and six culture positive individuals per sampling occasion. One of the calves that was housed indoors was positive in faecal culture on four consecutive samplings." (One big limitation on this study is the very small sample size. There were only 6 calves in each group, which is a very small number so that makes this data somewhat less able to be used to draw widely-applicable conclusions.)

10. Animal petting zoos as sources of Shiga toxin-producing Escherichia coli, Salmonella and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae -   https://pubmed.ncbi.nlm.nih.gov/33382208/ - “Animal petting zoos and farm fairs provide the opportunity for children and adults to interact with animals, but contact with animals carries a risk of exposure to zoonotic pathogens and antimicrobial-resistant bacteria. The aim of this study was to assess the occurrence of Shiga toxin-producing Escherichia coli (STEC), Salmonella, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and methicillin-resistant Staphylococcus aureus (MRSA) in animal faeces from six animal petting zoos and one farm fair in Switzerland. Furthermore, hygiene facilities on the venues were evaluated. Of 163 faecal samples, 75 contained stx1, stx2 or stx1/stx2 genes, indicating the presence of STEC. Samples included faeces from sika deer (100%), sheep (92%), goats (88%), mouflons (80%), camels (62%), llamas (50%), yaks (50%), pigs (29%) and donkeys (6%), whereas no stx genes were isolated from faeces of calves, guinea pigs, hens, ostriches, ponies, zebras or zebus. Salmonella enterica subsp. enterica serovar Stourbridge (S. Stourbridge) was detected in faecal samples from camels. A total of four ESBL-producing E. coli strains were isolated from faeces of goats, camels and pigs... This study provides data that underscore the importance of hygiene measures to minimize the risk of transmission of zoonotic pathogens and MDR, ESBL-producing E. coli to visitors of animal petting venues.” 

11. Investigations on Transfer of Pathogens between Foster Cows and Calves during the Suckling Period - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8469241/ - “The present study aimed to compare the pathogens detected in the mammary glands of the foster cow with those in the oral cavities of the associated foster calves and to evaluate the resulting consequences for udder health, calf health and internal biosecurity... Transmission of P. multocida and S. aureus probably occurred during suckling. For S. sciuri and Sc. suis, environmental origins were assumed. Transmission from dam to foster cow with the suckling calf as vector could not be clearly demonstrated.”

12. Effects of early separation on the dairy cow and calf: 2. Separation at 1 day and 2 weeks after birth - https://pubmed.ncbi.nlm.nih.gov/11179551/ - “Behavioural observations were conducted on 24 Holstein dairy cow-calf pairs during the first 24h after separation. Before separation, cow-calf pairs were generally inactive. After separation, cows from the late-separation treatment group showed higher rates of calling, movement and placing the head outside the pen, than cows in the early-separation group.”

13. The effect of individual versus pair housing of dairy heifer calves during the preweaning period on measures of health, performance, and behavior up to 16 weeks of age - https://pubmed.ncbi.nlm.nih.gov/33358809/ - Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing. 

Managing Pathogen Risks from Fresh Cows and Does

For farmers who are producing raw milk for direct human consumption, it is important to understand the risks related to fresh cows and does. Freshening is a time of tremendous change as the udder moves into the production of colostrum and milk.  During this time of transition while the milk supply is being established, there is a higher likelihood of mastitis and pathogens being present in the udder. Although pathogens in well-produced raw milk are rare, they are still an important consideration and we encourage all raw milk farmers to take pathogens seriously.  

Fresh Cows and Pathogens

Our understanding of the increased pathogen risks in fresh cows/does is largely based on test data from RAW Farm in California. This dairy was founded by RAWMI Chairman Mark McAfee over 20 years ago, and it operates on a different scale than most raw milk dairies.  RAW Farm is milking over 800 head of cattle and serving thousands of customers with distribution to over 400 stores in California. With this relatively large scale of raw milk production, RAW Farm has implemented some unique risk management strategies to ensure that the milk they provide is ultra-low-risk.

RAW Farm utilizes frequent pathogen testing as part of their risk management strategy. After having a positive E coli 0157:H7 test in a fresh cow’s milk years ago, RAW Farm started performing more frequent testing on individual fresh cows.  The overall test dataset shows that although pathogen detections are still rare, nonetheless fresh cows are more likely to test positive for pathogens than cows whose milk supply is well-established.

Based on this experience, RAW Farm chooses to err on the side of being extra careful, so they withhold the milk from fresh cows from their bulk tank for a minimum of 28 days and do multiple sets of pathogen tests on each fresh cow before adding her milk to the bulk tank.  However, we would not expect small-scale farms to undergo the same rigorous, expensive protocol. 

Withhold Milk for 5-7 Days, Then Check To Make Sure All is Well

Our general recommendation is for raw milk farmers to ensure that milk from fresh cows/does is not used for direct human consumption for a minimum of 5-7 days after freshening. After that period, we recommend that intentional methods be used to ensure there is no inflammation or mastitis present. Some methods that have been used successfully at other farms include:

• udder inspection for signs of inflammation

• testing such as mastitis, coliform, pathogen, and/or somatic cell count tests

There are several types of on-farm mastitis tests available, including 4-Way California Mastitis Test, Mas-D-Tec, and Udder Check.  When combined with visual inspection, these tests serve as a verification step prior to using the milk for direct human consumption.

Milk Fresh Cows and Does Last

Another risk management strategy is to make sure that the fresh cows/does are milked last, to ensure that any potential pathogens do not contaminate the milk from other animals.  After milking the fresh cows/does last, the milking machine should be rigorously cleaned, with special care taken for any complex parts such as valves.

What to Do With The Withheld Milk

Right after freshening, the colostrum should ideally be fed to calves/kids, who will benefit from its immune-system strengthening properties. Once the colostrum has cleared, and assuming that the milk looks healthy, this milk can be used for making inherently-low-risk foods such as butter or aged-cheeses. Due to their low moisture content and low pH, these foods are very unlikely to harbor pathogens.   

Acknowledge the Risk and Make a Plan

Managing the increased pathogen risks for fresh cows/does need not be complicated.  Just as for other potential risks, we recommend that farmers acknowledge the risk and make a plan for how to handle it.  This will reduce the likelihood of anything going wrong, for the benefit of both the customers and farmers. With proper risk management, low-risk raw milk is achievable.

Want help in optimizing your own production of raw milk? Check out our FREE Listing Program for farmers!

This article was published in the May 2023 issue of Graze Magazine.

Join Us for Raw Milk Training in Oregon June 17-18

On June 17-18 2022, the Raw Milk Institute (RAWMI) will be providing Raw Milk Risk Management training in Oregon. This training is will be done in collaboration with Cast Iron Farm (RAWMI Listed farm in Oregon).

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About the Training

This 2-day intensive RAWMI training workshop will focus on the benefits of raw milk, grass-to-glass identification of risks, development of a risk management plan, and lessons learned from other raw milk dairies. It is our goal to assure that raw milk is safe and continues to be freely available for both farmers and consumers in Oregon.

The training will be hosted at Cast Iron Farm in McMinnville, Oregon. We'll be providing lots of practical tips for the production of safe raw milk. The training will include formal presentations as well as demonstrations and tours at Cast Iron Farm. This training has been shown to reduce outbreaks and illnesses, increase safety, and lower insurance costs.

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Cost and Registration

The cost for this 2-day training workshop is only $35.

If the cost is a barrier, feel free to contact Christine at Cast Iron Farm to learn about potential scholarships.

You can register for the class here:

http://castironfarm.com/rawmi-training-june-2023/

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Class Schedule

Saturday June 17th

• 9:30am - Arrival and introductions

• 10:00am - 45 minute presentation by Oregon Department of Ag outlining the new CAFO regulations for anyone owning dairy animals.  This will include time for Q&A. If you do not feel comfortable attending a presentation given by the state agency, feel free to join us after lunch.

• noon-1pm - Light lunch and snacks

• 1pm-3pm - RAWMI presentation by Mark McAfee on health benefits of raw milk, safety and risks of raw milk

• 3pm-3:20pm - Stretch break

• 3:30pm-5pm - RAWMI presentation on raw milk risk management from grass-to-glass

Sunday June 18th

• 9:30am - Milking demonstration and tour of Cast Iron Farm

• 10:30am-noon - RAWMI presentation about raw milk testing and and building a successful raw milk business

• noon-1pm - Light lunch and snacks

• 1pm - One-on-one questions and consultations with RAWMI to answer all your questions

Sunday afternoon tours of Godspeed Hollow, another RAWMI listed farm 20 minutes from Mcmminnville, can be arranged by appointment for those interested.

Rapid Chilling of Raw Milk Lowers Pathogen Risks and Improves Shelf-Life

For raw milk production, risk management and customer satisfaction go hand-in-hand.  Many of the strategies that result in low-risk raw milk also work well to keep customers happy with delicious, long-lasting milk. Rapid chilling is one such strategy that lowers the risk of pathogens while also improving the flavor and shelf-life of raw milk.

Although pathogens in well-produced raw milk are rare, they are still an important consideration and we encourage all raw milk farmers to take pathogens seriously.  The four main pathogens of concern that can be found in raw milk are E coli 0157:H7, Salmonella spp., Campylobacter spp., and Listeria monocytogenes. Illnesses from these pathogens can be serious or even fatal. 

In the rare case when pathogens are present in well-produced raw milk, illness will still not occur unless the pathogen load (or amount of pathogen present) is high enough to produce illness. If it is present in a small enough quantity, even the most virulent pathogen will not produce illness.  Generally, the presence of a single virulent bacterium is not sufficient to cause illness, and different pathogens have varying thresholds at which they must be present to induce human illness. 

However, bacteria multiply rapidly at warm temperatures and can double their count in as little as 20 minutes. At cold temperatures, bacteria growth slows down dramatically.  This means that farmers can greatly reduce the number of bacteria present in raw milk by quickly chilling the milk right after milking time. 

Aim for Chilling to 35-40 °F in Less Than an Hour

Our general recommendation is for farmers to chill their raw milk to 35-40 °F within an hour of milking.  This helps in ensuring that any bacteria present in the raw milk do not have much time in which to multiply.

Refrigerators do not generally work well for rapidly chilling raw milk.  Depending on the size of the milk jar or jug, it may take a few hours for warm milk to cool down to under 40 degrees in the refrigerator. Freezers also do not generally work well for chilling milk because the milk may freeze and break the glass jars. 

In order to achieve cold milk in a short time, other methods are needed. We work closely with dozens of farmers, and have seen that rapid milk chilling is achievable no matter the size of the farm.  Here are some of the different ways in which farmers can rapidly chill their raw milk to 35-40°F in an hour or less.  

Ice-and-Water Bath for Rapid Milk Chilling on Micro-Dairies

For small-scale farms, an ice-and-water bath can work well for milk chilling. A chest cooler can be used to hold the ice-and-water bath.  When using this method, there are a few important things to pay attention to:

• The milk jars should be submerged in the cold ice-and-water, but make sure that the water level does not reach lid of the milk container. Otherwise, there may be problems with water comingling with the milk in the jars.

• The size of the milk jar will make a big difference in how long it will take the milk to chill down.  We recommend that farmers use milk jars that are no larger than ½ gallon, or else the chilling time will be too lengthy.

• Some farmers who do not have ice maker machines have preferred to use either stainless steel ice cubes (which can be sanitized in the dishwasher) or frozen water bottles which can be reused over and over again.

• Make sure there is enough cold ice water to rapidly chill the milk.  If there are too many milk jugs in relation to the amount of ice water, then the chilling will not be quick enough.

• Some farmers like to add in a small submersible water pump (such as an aquarium or pond pump) to circulate the water in their ice water bath for quicker chilling. 

• Whatever method you use, you can check to see whether the milk is chilling rapidly enough by measuring the temperature in the middle of your milk jars after an hour.   
  

Bulk Milk Tanks

Bulk tanks are another option for milk chilling. Small bulk tanks can hold up to 15 gallons of milk, and many other sizes are available for farmers who are producing larger quantities of milk.  Bulk tanks with integrated cooling systems can quickly chill the milk to the desired temperature. When using a bulk tank, farmers need to be aware of the following:

• Bulk tanks need to be sized appropriately, or else there can be problems with the milk freezing if there is too little quantity of milk relative to the size of the tank.

• Milk stacking occurs when milk from multiple milkings is poured into the bulk tank. This can result in increased bacteria counts as the milk in the tank is re-warmed each time fresh milk is added.  Furthermore, milk stacking increases the risk of contamination from one batch of milk to another, thereby increasing the potential damage done by the presence of any undesirable bacteria/pathogens. We recommend that farmers minimize milk stacking by bottling their milk after every 1-3 milkings.

• Bulk tanks must be thoroughly cleaned after each time the milk is bottled.  The valve on the bulk tank, in particular, needs to be completely disassembled and scrubbed clean to ensure that it does not harbor bacteria. 

Sophisticated Chilling for Larger Farms

Larger farms may choose to use sophisticated chilling equipment, such as plate chillers.  These chillers will cool the milk down rapidly in just a few minutes before it even enters the bulk tank.  Farmers using plate chillers need to be aware of the following:

• Complex equipment can create more opportunities for bacteria biofilms to grow in nooks and crannies. Therefore, thorough cleaning is essential for plate chillers in between milkings.

• A clean-in-place (CIP) system will be required for thoroughly cleaning the plate chiller.  We recommend that farmers work with a dairy supply consultant to optimize the CIP for their individual pipeline systems. This should include a tepid rinse, followed by a hot wash with alkaline detergent, followed by a warm acid rinse. 

• The temperature of the water used for the hot alkaline wash will decrease as the water flows through the system, thereby reducing the effectiveness of the cleaning solution. It is recommended to ensure that the temperature of the wash water is at least 120 degrees at the outlet of the system.

• Over time, bacteria biofilms can become resistant to specific cleaners, especially in pipeline systems.  Therefore, it is recommended to periodically “shock” pipeline systems by using different alkaline and acid cleaners about once a month.

Rapid Milk Chilling is Achievable

Rapid milk chilling is an important strategy for risk reduction with raw milk.  As we have described, rapid chilling is achievable no matter the size of the farm. Besides reducing the risk of high bacteria counts in the milk, rapid chilling can also result in a longer shelf-life for the milk and help in preventing off flavors. Rapid chilling is a Win-Win for both farmers and customers.

This article was published in the April 2023 issue of Graze Magazine.

VIDEO: On-Farm Raw Milk Testing with Charm Sciences Peel Plates

The Raw Milk Institute is pleased to share with you this new video for learning how to do on-farm bacterial testing of raw milk. This video was put together by Kelsey Barefoot, who is on the RAWMI Board of Directors and tests the raw milk from her own farm in an on-farm lab.

Regular bacterial testing is one of the keys to ensuring that raw milk is low-risk. On-farm testing is economical and valuable for raw milk farmers, as it allows them to test their milk more frequently and detect trouble spots before they become a bigger issue.

This new video will show you:

• Materials needed for on-farm lab testing

• How to perform on-farm lab testing of raw milk using Charm Sciences peel plates

• How to interpret the results

The bacterial tests performed in an on-farm lab (coliform and Standard Plate Count) are used to provide a general indicator that milk is being produced in a way that is unlikely to lead to pathogens and pathogen growth. RAWMI Common Standards aim for a rolling three-month average of less than 5,000 cfu/mL for Standard Plate Count and less than 10 cfu/mL for coliforms.

For more information about on-farm milk testing, including materials lists and written procedures, go here:

On-Farm Lab Testing for Raw Milk Farmers

On-farm labs are a valuable and economical tool for raw dairy farmers

The three pillars of the Raw Milk Institute’s (RAWMI) Method for safe, low-risk raw milk are 1) farmer mentoring, 2) risk management plan for each farm, and 3) regular bacterial testing of raw milk.  This method works well and has been documented to lead to a significant reduction in raw milk-related illnesses and outbreaks. Researchers who have studied the safety of raw milk produced with the RAWMI Method have concluded that “raw milk can be produced with a high level of hygiene and safety.”

RAWMI’s farmer mentoring program and assistance in developing an individualized risk management plan are free for all farmers. However, milk testing costs can be an ongoing financial burden which make small-scale farmers hesitant to test their milk often. But there is a great solution to this: on-farm testing!

What is an On-Farm Lab?

Pioneered by Edwin Shank from The Family Cow dairy in Pennsylvania, on-farm labs are a tremendous resource for dairy farmers. On-farm labs can be set-up on the countertop in a small, clean workspace. Once the lab area is ready, farmers can easily test their milk for coliforms and Standard Plate Count with the use of a small incubator. 

Set-up costs for on-farm labs are in the range of $800-$1,000.  RAWMI is currently offering grants of up to $500 to offset lab costs for farmers who are Listed or going through our Listing program. After the initial set-up costs, raw milk testing costs are only $1-$3 for each test performed in the on-farm lab.

Benefits of On-Farm Labs

On-farm labs have numerous benefits for raw milk farmers. As Mark McAfee says, “What gets measured gets done.”  Ignorance is not bliss when it comes to raw milk. Testing allows farmers to dependably produce low-risk raw milk with confidence.

With on-farm labs:

• Farmers can test their milk for coliforms and Standard Plate Count.

• Ongoing testing costs are only $1-$3 per test.

• Farmers can inexpensively test their milk as often as desired, so they can identify patterns in their bacterial counts which help in identifying trouble spots ahead of time.

• The effects of new equipment or procedures on bacterial levels can be evaluated.

• Farmers can test more often as needed for troubleshooting high bacteria counts.

• Annual water tests can also be performed.

The bacterial tests performed in an on-farm lab (coliform and Standard Plate Count) are used to provide a general indicator that the milk is being produced in a way that is unlikely to lead to pathogens and pathogen growth.  The RAWMI Common Standards aim for a rolling three-month average of <5,000 cfu/mL for SPC and <10 cfu/mL for coliforms.

NOTE: RAWMI does not recommend on-farm testing for specific pathogens (such as e coli 0157:H7, salmonella, listeria mono, etc), due to potential hazards from accidental release of pathogens on the farm.

Two Different Systems for On-Farm Testing

There are currently two different systems for performing on-farm testing, developed by 3M (now owned by Neogen) and Charm Sciences.  Both of these systems work well for on-farm raw milk testing, and the basic lab equipment (incubator, lightbox, magnifier, etc) are the same with either system.

Neogen’s testing system uses petri-films and provides results in 24 hours.  Unopened packages of Neogen petrifilms are stored in the refrigerator or freezer for up to 18 months, with opened packages being stored at room temperature for up to one month.

Charm Sciences testing system uses peel-plates and provides results in 24-48 hours.  The peel plates can be stored at room temperature for up to 12 months. Testing costs are currently a bit lower with Charm Sciences peel-plates than with Neogen petrifilms. 

How to Do On-Farm Bacterial Testing for Raw Milk

Here are several free resources for farmers who are interested in doing on-farm milk testing.

RAWMI VIDEO: How to Test Raw Milk with Charm Sciences Peel Plates

Charm Sciences Peel Plate User Guide from The Barefoot Cow Dairy

5-page materials list and procedures for performing on-farm testing with Charm Sciences peel plates

On-Farm Lab Testing: A Guide to Raw Milk Bacteria Testing from Six S Dairy

Comprehensive 20-page guide to on-farm testing with Neogen (3M) Petri-Films, including materials list, procedures, results interpretation, and tips for success

Raw Milk Lab Materials List from The Family Cow Dairy

Short 1-page list of materials required for performing on-farm testing with Neogen (3M) Petri-Films

Raw Milk Lab Procedures from The Family Cow Dairy

Short 2-page list of procedures for on-farm lab testing with Neogen (3M) Petri-Films

Other Helpful Resources

• VIDEO: Charm Sciences Peel Plates

• 3M (Neogen) coliform interpretation guide

• 3M (Neogen) SPC interpretation guide

• VIDEO: 3M (Neogen) PetriFilms

• VIDEO: 3M (Neogen) Petrifilms vs Charm Sciences Peel Plate side-by-side demo

Why is Predictive Microbiology Crucial to Raw Milk Risk Assessment?

Earlier this month, readers of the feature article written by Sarah Smith, my colleague at the Raw Milk Institute (RAWMI), learned about pathogen growth in raw milk. RAWMI contracted with an independent laboratory to conduct a pilot study with an experimental design based on published studies on Predictive Microbiology, the science supporting models of the growth and survival of microbes under different experimental conditions. This article provides readers with more information about what Predictive Microbiology is and why it is important to dairy farmers and raw milk consumers in the 21st century.

Why is Predictive Microbiology important to dairy farmers and raw milk consumers?

Awareness of Predictive Microbiology is important because pathogen growth is modeled in the Exposure Assessment portion of Microbial Risk Assessments (MRAs; FDA/FSIS, 2003; FSANZ, 2009), and the models selected often intentionally overestimate pathogen growth by design, as ‘fail-safe’ models (Tamplin et al., 2002; Coleman et al., 2003a,b; Ross et al., 2003; Coleman, 2021). In other words, regulators rely on predictive microbiology models in estimating the level of risk, and the models that have been available thus far typically intentionally overestimate the risk of pathogen growth. 

The advantage for risk managers and regulators in selecting policies based on ‘fail-safe’ models that overestimate growth is the appearance of minimizing public health breaches or ‘failures’ (e.g., illnesses or outbreaks) if anything goes wrong along the food safety chain from production to consumption. The disadvantage for dairy farmers and raw milk consumers is that the growth models applied for raw milk MRAs are wrong, based on intentionally biased experiments that overestimate actual pathogen growth in raw foods and thus overestimate risk of illness to consumers.

For a quick overview of MRA, see the text box and figure in the forthcoming May 2022 article entitled Raw Milk Risks from a Microbiologist’s Perspective that I prepared for Weston A. Price Foundation’s Wise Traditions journal.

Science of Predictive Microbiology

Microbiologists including those at the USDA’s Agricultural Research Service in Wyndmoor, PA, began designing ‘factorial’ experiments for modeling pathogen growth in the 1990s, selecting rich nutrient culture broths amenable to testing a wide variety of levels of different ‘factors’ that influence microbial growth. The study designs were inexpensive and accurate, compared to more expensive and more complex analysis for different foods. The data from these experiments are generally well validated experimentally: that is, for growth in pure culture broths.

Such data formed the basis of free online tools for predicting growth, including the USDA’s Pathogen Modeling Program (PMP). The experiments were designed to include multiple levels of different factors including pH and salt or water activity that are similar to levels that can be measured in foods. The advantages of such tools based on broth culture experiments for government and academic risk assessors are that they might extrapolate the broth culture growth models to foods with similar levels of factors measured, and assume the models are still accurate. This could be beneficial because conducting pathogen growth studies in foods under diverse conditions of temperature and storage is expensive and time consuming.

Screenshot from USDA PMP

Now, with access to PMP, the risk assessor can select the inputs from those tested in multiple factor broth culture experiments from the sliders illustrated in the screen shot from PMP on the left. I illustrated a growth scenario with an appropriate refrigeration temperature (5°C or 41°F, from a range of 5-42°C or 41-107.6°F) and a pH (6.5, from a range of 4.5-8.5) relevant to raw milk.

The first problem for dairy farmers and raw milk consumers is that models based on optimal growth of pathogens in pure cultures described by rich broth culture models overestimate actual pathogen growth in raw milk. As early as 1997, university researchers published experimental results reporting that the rate of growth of the pathogen E. coli O157:H7 was significantly slower in raw milk than pasteurized (Wang et al., 1997). The authors noted that the difference in growth rates was likely due to the natural microbes in raw milk that outcompete pathogens and limit their growth in raw, not pasteurized, milk.

Another problem for farmers and consumers is that the broth culture study designs are typically biased by inclusion of only high initial pathogen levels (> 3 log10 colony forming units (CFU) per mL or >1,000 CFU/mL, from a range of 3 to 5.9 log10 CFU/mL).  Even in rich culture broth, growth rates are lower at low inoculum levels (~1 CFU/mL; Coleman et al., 2003). Biased growth models (based on rich nutrient broth, high initial inoculum, and/or absence of natural milk microbiota) result in biased MRAs that overestimate raw milk risks.

You may not be surprised to learn that some microbial risk assessment teams, including the Food Standards Australia New Zealand team (FSANZ, 2009), selected rich culture broth studies (Salter et al., 1998; Ross et al., 2003) that measured growth of harmless or commensal E. coli strains that are part of our healthy gut microbiota, not even pathogenic strains like O157:H7 that can cause illness and grow at slower rates. FSANZ excluded an available study on growth of the pathogen E. coli O157:H7 itself in raw and pasteurized milk reported by Wang and esteemed food scientist Mike Doyle at the University of Georgia (Wang et al., 1997).

Why do you think the FSANZ team decided not to cite Mike Doyle’s study, a study they should have known about? Likely because it measured lower pathogen growth rates in raw milk than in pasteurized milk (and broth). Thus, it seems that FSANZ likely excluded the study because the results did not support their notion that raw milk is inherently dangerous, and more dangerous than pasteurized milk. A short plain language summary prepared by the Australian Raw Milk Movement (ARMM) and the full 73-page technical report that I prepared for them (Coleman, 2021) are both available on the ARMM website. See the technical report for the more detailed section on pathogen growth and microbial ecology (pp. 30-40 of the 73-page report).

Why is Inoculum Level Important to Predict Growth in Raw Milk?

Well-produced raw milk has relatively low levels of coliform and aerobic bacteria. Farmers who follow RAWMI’s Common Standards for raw milk aim for coliform counts of <10 CFU/mL and Standard Plate Counts of <5,000 CFU/mL. However, don’t let these low coliform counts or low Standard Plate Counts in raw milk fool you.

Raw mammalian milks are complex ecosystems with dense and diverse microbes that benefit health. The natural microbes in raw milks have different requirements for culturing them, so studies that rely on specific culture media for assessing what microbes are present in raw milk are biased. The development of genomic methods that estimate presence of microbial genes or gene products in raw milks without culturing are more reliable for describing the raw milk microbes or microbiota (Oikonomou et al, 2020). Such studies are transforming our understanding of the microbiota of many natural systems in the recent decade, including raw mammalian milks.

The dense and diverse microbiota predominant in raw milk from healthy mammals is illustrated in the figure below by Oikonomou and colleagues (2020; authors’ Figure 2, pg. 4 of 15). The bacteria listed in red text were identified in the milk microbiota from all five types of mammals, bacteria in yellow from 3 or more mammals, and bacteria in blue in less than three mammals. None of these bacteria were identified as pathogens, but rather are natural microbes that appear to benefit human and animal offspring (and adult humans) by ‘seeding and feeding’ the gut. In other words, raw milk ‘seeds’ the gut with beneficial microbes and ‘feeds’ gut and microbial cells with nutrients. The raw milk microbiota also stimulates proper maturation and function of immune, neural, and respiratory systems (Coleman et al., 2021a,b; Dietert et al., 2022).

Oikonomou, et al., “Milk microbiota: what are we exactly talking about?” Frontiers in Microbiology

Predominant beneficial microbes including Pseudomonas, Staphylococcus, and certain lactic acid bacteria or LABs (including not just the familiar Lactobacillus, but also 11 other microbes: Lactococcus, Enterococcus, Streptococcus, Carnobacterium, Vagococcus, Leuconostoc, Oenococcus, Pediococcus, Tetragonococcus, Aerococcus and Weissella) are known to outcompete specific pathogens at refrigeration temperatures (Coleman et al., 2003a; Reuben et al., 2020).

A recent study in the Journal of Dairy Science (Reuben et al., 2020) illustrates the importance of incorporating data on the microbiota and microbial ecology of raw milks into Predictive Microbiology models and MRAs.  The authors demonstrated not merely suppression of growth of all pathogens tested (E. coli O157:H7, L. monocytogenes, and Salmonella) by LAB strains isolated from raw cow milk, but also ‘competitive exclusion’ of these pathogens inoculated at both 103 and 106 log10 CFU/mL. Clearly, the natural milk microbiota influences growth of pathogens.

In summary, the raw milk ecosystem differs greatly from sterile nutrient broth. If an MRA relies on pathogen growth models based on broth cultures, be skeptical of its value for predicting pathogen growth in raw milk. Pathogen growth rates in raw milk are likely lower due to suppression or exclusion of pathogens by the natural raw milk microbiota and compounds produced by these beneficial microbes.

How do Microbes in Raw Milk Outcompete and Exclude Pathogens?

The peer-reviewed literature is expanding as researchers document the mechanisms or pathways by which the raw milk microbes benefit health. Microbes in raw milk produce vitamins and enzymes that enhance gut health. Microbes also produce antimicrobial compounds including proteins (bacteriocins) and organic acids like lactic acid that reduce pH and indirectly suppress pathogen growth, modulate the immune system, and reduce inflammation. 

The natural raw milk microbiota also enhances gut mucosal barrier function, and competes with pathogens in the gut nutritionally and spatially (colonizing potential bacterial binding sites, enhancing ‘colonization resistance’ to pathogens, and reducing pathogen infection rates). Consider recent evidence for benefits and risks for the breastmilk microbiota (Coleman et al., 2021a,b) and the cow milk microbiota (Dietert et al., 2022). A large body of evidence also exists that documents mechanisms of interference of LABs with pathogens, including pathogen virulence expression.

Want More Perspectives from a Microbiologist and Risk Assessor?

Feel free to contact me for more information at peg@colemanscientific.org.

Key References Cited

1. Coleman, M. E., Sandberg, S., & Anderson, S. A. (2003a). Impact of microbial ecology of meat and poultry products on predictions from exposure assessment scenarios for refrigerated storage. Risk Analysis: An International Journal, 23(1), 215-228.

2. Coleman, M. E., Tamplin, M. L., Phillips, J. G., & Marmer, B. S. (2003b). Influence of agitation, inoculum density, pH, and strain on the growth parameters of Escherichia coli O157: H7—relevance to risk assessment. International Journal of Food Microbiology, 83(2), 147-160.

3. Dietert, R. R., Coleman, M. E., North, D. W., & Stephenson, M. M. (2022). Nourishing the Human Holobiont to Reduce the Risk of Non-Communicable Diseases: A Cow’s Milk Evidence Map Example. Applied Microbiology, 2(1), 25-52.

4. Food Standards Australia New Zealand (FSANZ). (2009). Microbiological Risk Assessment of Raw Cow Milk. Available at: https://www.foodstandards.gov.au/code/proposals/documents/-p1007%20ppps%20for%20raw%20milk%201ar%20sd1%20cow%20milk%20risk%20assessment.pdf.

5. Oikonomou, G., Addis, M. F., Chassard, C., Nader-Macias, M. E. F., Grant, I., Delbès, C., ... & Even, S. (2020). Milk microbiota: what are we exactly talking about? Frontiers in Microbiology, 11, 60.

6. Ross, T., Ratkowsky, D. A., Mellefont, L. A., & McMeekin, T. A. (2003). Modelling the effects of temperature, water activity, pH and lactic acid concentration on the growth rate of Escherichia coli. International Journal of Food Microbiology, 82(1), 33-43.

7. Reuben, R. C., Roy, P. C., Sarkar, S. L., Alam, A. R. U., & Jahid, I. K. (2020). Characterization and evaluation of lactic acid bacteria from indigenous raw milk for potential probiotic properties. Journal of Dairy Science, 103(2), 1223-1237.

8. Salter, M. A., Ross, T., & McMeekin, T. A. (1998). Applicability of a model for non-pathogenic Escherichia coli for predicting the growth of pathogenic Escherichia coli. Journal of Applied Microbiology, 85(2), 357-364.

9. Tamplin, M. L. (2002). Growth of Escherichia coli O157: H7 in raw ground beef stored at 10 C and the influence of competitive bacterial flora, strain variation, and fat level. Journal of Food Protection, 65(10), 1535-1540.

10. Wang, G., Zhao, T., & Doyle, M. P. (1997). Survival and growth of Escherichia coli O157: H7 in unpasteurized and pasteurized milk. Journal of Food Protection, 60(6), 610-613.

How Well Do Pathogens Grow In Raw Milk?

Low Risk of Pathogens in Intentionally-Produced Raw Milk

Despite raw milk’s association with decreased rates of asthma, allergies, eczema, ear infections, fever, and respiratory infections, government agencies in countries such as the USA, Canada, and Australia are still biased against raw milk. These Government agencies warn against raw milk consumption and, in some places, they even impose an outright ban on raw milk with potential heavy penalties and imprisonment for raw milk farmers.

The rationale that these Government agencies cite against raw milk is their belief that raw milk consumption leads to high rates of foodborne outbreaks, illnesses and deaths.  However, this belief is outdated and conflicts with the most up-to-date peer-reviewed research which has found that carefully produced raw milk is a low-risk food which is fundamentally different from pre-pasteurized milk. 

The table below contrasts pathogen test data from pre-pasteurized milk vs. carefully-produced raw milk intended for direct human consumption. As illustrated in the table, pathogen testing of pre-pasteurized milk samples has detected pathogens in up to 33% of samples.  In contrast, there were zero pathogens detected in thousands of milk samples from raw milk intended for direct human consumption. It is clear from this test data from bulk tanks or milk silos that the risk profile of pre-pasteurized milk is categorically different from raw milk intended for direct human consumption.

Data courtesy British Columbia Herdshare Association

Pathogen Loads and Illness

Carefully-produced raw milk has a low-risk of containing pathogens, but there is no such thing as a perfectly safe food. A CDC analysis of foodborne illnesses from 2009-2015 showed that the top food categories commonly linked to illnesses were chicken, pork, and seeded vegetables. Pasteurized milk is not perfectly safe, either, and is implicated in foodborne illnesses and outbreaks. 

In the very rare case that a pathogen could be present in carefully-produced raw milk, in order for a pathogen to cause illness four variables must align:

• A pathogen must be present

• The pathogen must be virulent and capable of producing harmful effects

• The pathogen load must be high enough to produce illness

• The person must be susceptible to the pathogen

If it is present in a small enough quantity, even the most virulent pathogen will not produce illness.  The presence of a single virulent bacterium is not sufficient to cause illness, and different pathogens have varying thresholds at which they must be present to induce human illness. 

For instance, even though Listeria monocytogenes is a known foodborne pathogen, the European Union allows Listeria up to 100 bacteria/gram in foods that do not permit growth because it is known that Listeria in lesser amounts is not sufficient to cause illness.

Some of the data cited by Government agencies against raw milk includes pathogen growth studies where it was found that pathogens multiply greatly over time.  However, these studies are not actually applicable to carefully-produced raw milk because they were performed in nutrient-rich broth instead of milk, they used tremendously high amounts of pathogens (such as 10 log 7, which corresponds to ten million pathogenic colony-forming units (CFU) of bacteria per mL), or they did not account for cold temperature storage.

Need for a NEW Pilot Study on Pathogen Growth for Raw Milk

In order to generate a stronger scientific basis for assessments of risks of pathogen growth in raw milk, the Raw Milk Institute (RAWMI) recently commissioned a pilot study on pathogen growth performed by an independent 3rd party lab certified to perform pathogen testing, Food Safety Net Services (FSNS).  RAWMI Advisory Board member Peg Coleman provided technical input on the study design based on predictive microbiology (Coleman et al., 2003a) and risk assessment (Coleman et al., 2003b) studies that she had conducted at the University of Maryland Eastern Shore and published through the USDA Agricultural Research Service. The new pilot study was partially paid for through donations.   

In this new pilot study, samples of well-produced raw milk were purposely inoculated with the four main pathogens of concern for raw milk: E coli 0157:H7, Salmonella spp., Campylobacter spp., and Listeria monocytogenes. Raw milk was inoculated at two levels (high and moderate counts per mL). The objective of this new pilot study was to document growth characteristics of these pathogens in carefully produced raw milk over a period of 14 days when stored at the refrigeration temperature recommended by FDA and USDA: 40°F (4.4 °C). The number of pathogenic bacteria present in the raw milk were counted on days 0, 3, 6, 9, 12, and 14.

Highlights of NEW Pilot Study Design

• The temperature for this study was chosen because 40°F (4.4°C) is the recommended maximum temperature for a home refrigerator.

• Inoculum Level I: target <10 CFU/mL. Although the study design called for inoculation with <10 CFU/mL, the actual amounts used in the study were measured in the range of 22-162 CFU/mL, thus a moderate level inoculum.

• Inoculum Level II: target 1,000 CFU/mL. Although the study design called for inoculation with 1,000 CFU/mL, the actual amounts used in the study were measured in the range of 600-8,300 CFU/mL.

Results of the NEW Pilot Study

The tables below show the results of the study at Inoculum Levels I and II.

Table of Results from Inoculum Level I, from FSNS Report, Determination of Growth Rate of Salmonella enterica spp., E. coli O157:H7, Campylobacter spp., and Listeria monocytogenes in Raw Milk

Table of Results from Inoculum Level II, from FSNS Report, Determination of Growth Rate of Salmonella enterica spp., E. coli O157:H7, Campylobacter spp., and Listeria monocytogenes in Raw Milk

The most relevant finding of the study is that at moderate Inoculum Level I, no pathogen growth is observed through at least 6 days of refrigerated storage. The very high Inoculum Level II results are less important to risk assessors since these levels of pathogens are not observed in naturally contaminated raw milk.

Over the study period of 14 days, the counts per mL of E coli 0157:H7, Salmonella spp., and Campylobacter spp. decreased over time. These results indicate that, when stored at the recommended refrigerator temperature, moderate to high counts of E coli 0157:H7, Salmonella spp., and Campylobacter spp. did not multiply over time in raw milk. Listeria monocytogenes exhibited some growth in this study after 9 days of refrigeration at both moderate and high level inoculum levels.

Click the button below to download the full report from FSNS, Determination of Growth Rate of Salmonella enterica spp., E. coli O157:H7, Campylobacter spp., and Listeria monocytogenes in Raw Milk.

Further Research

This study was designed as a small pilot study, and further research is needed to draw more-robust conclusions. Analysis of the NEW pilot study data are in preparation for submittal to a peer reviewed journal. Peg Coleman will also be providing a more detailed analysis of the study.

The new pilot study and the publication are intended to support a grant proposal to fund a full study that includes multiple producers of raw, lightly pasteurized, and typical pasteurized milks, with daily sampling after low and high inoculum levels. Nonetheless, the results of this NEW pilot study serve to provide an initial basis for challenging incorrect assumptions of the past that overestimated the growth of pathogens in clean, cold raw milk produced for direct human consumption by careful, trained producers.