USDA:- Agricultural Research Service.


Governed by United States Department of Agriculture
Mission Statement"As the chief in-house scientific research arm of the USDA, the Agricultural Research Service has a mission to conduct research to develop and transfer solutions to agricultural problems of high national priority and provide information access and dissemination to ensure high-quality, safe food, and other agricultural products, assess the nutritional needs of Americans, sustain a competitive agricultural economy, enhance the natural resource base and the environment, and provide economic opportunities for rural citizens, communities, and society as a whole."
Acting DirectorEdward B. Knipling
Web Page

ARS has primary responsibility to:

  • Provide initiative and leadership in agricultural research.

  • Conduct research on broad regional and national agricultural and related problems.

  • Conduct research in support of Federal action and regulatory agencies.

  • Provide technical expertise to meet national food, food safety, and environmental emergencies.

  • Serve as an agricultural science resource to the executive and legislative branches.

The Food Safety Initiative (FSI)  highlights food safety and, in particular, the control of food borne pathogens, as an important concern of the entire Federal Government. Reduction in the potential health risks to consumers from human pathogens in food is the most important food safety goal. ARS has the resources, including appropriate physical facilities, state-of-the-art laboratory equipment, and scientific expertise and experience to address and make significant contributions in all of these areas.

Paper TrailSee PARA's Paper TrailNew window link indicator for communications between PARA and various agencies of the U.S. Government.

Before proceeding further, we would encourage you to read the Important Developments Page prior to reading the rest of this webpage. This will give you some background which may be helpful in evaluating the action or inaction taken by ARS, and to assess PARA's Concerns in light of significant developments that have taken place around the world.


PARA's Concerns

USDA-ARS pasteurization research of dubious value

In 1996, Dr.  Stabel, of the USDA Agricultural Research Service, and a member of the National Johne's Working Group, conducted a laboratory simulation of commercial High Temperature Short Time (HTST) milk pasteurization process. See here for the full text of the USDA-ARS researchNew window link indicator.

This simulation study is the basis upon which the FDA Center for Food Safety and Applied Nutrition has decided dairy safety policy for the United States. The USDA ARS researchers found that MAP did not survive their simulation of pasteurization, a result that is in disagreement with almost every other pasteurization study ever conducted, including studies from the USA, England, Northern Ireland and Australia.

To read what other scientists have stated about the USDA-ARS research, see the following articles/letters

On close examination of the methodologies of the USDA ARS research, it is not difficult to understand why this research arrived at results that are in disagreement with every other study. Although the USDA researchers may have attempted to accurately simulate the conditions of commercial HTST pasteurization, what they failed badly to simulate was the conditions which MAP bacteria experience in real world milk taken from real-world cows with Johne's Disease. Among the additional injuries to which the USDA researchers subjected their bacteria were

  • Starved: The USDA researchers grew their supply of MAP bacteria "until they reached a concentration of 108 to 109 cells per ml (A540=1.15)", meaning that the bacteria had left "log-phase growth" and were in decline through lack of available nutrients, i.e. they were weakened by starvation before they were submitted to pasteurization.

  • Frozen: The USDA researchers stored their bacteria at -80oC (-112oF). Storage of MAP at this temperature has been demonstrated to kill a percentage of the bacteria, obviously leaving whatever bacteria were left alive "sublethally injured". When ice crystals form inside bacteria, the bacteria's DNA chains are severed and their cell walls are sliced open.

  • Blasted: The USDA researchers "sonicated" the MAP bacteria, at 35 watts for 15 seconds. Sonication is a process used in vaccine preparation to kill and rip apart bacteria, using resonant sound waves.

  • Heated: This is the only way that the USDA researchers should have treated the MAP bacteria, i.e. pasteurizing them. Note however that the USDA researchers used heat treatment of 72oC (+161.6oF), which is 0.3oC higher than the 71.7oC (161.0oF) used in commercial HTST pasteurization.

  • Blasted again: After pasteurizing the MAP bacteria, The USDA researchers "sonicated" the bacteria again at 35 watts for 15 seconds.

  • Inadequate culture time: The USDA researchers cultured their samples for a maximum of 12 weeks. In the veterinary world, MAP cultures are held for a minimum of 16 weeks before they are declared negative. This is particularly important for bacteria that have been "sublethally injured" by pasteurization (and "starvation", and "freezing" and "blasting"). In contrast, Sung and Collins cultured their samples for 8 months (32 weeks).

  • Inadequate culture media: The USDA researchers used solid culture media (HEYM), as opposed to the liquid culture media used by all other researchers in pasteurization studies. All of the other researchers that have studied pasteurization have found the liquid culture media to be more sensitive at recovering MAP that had been "sublethally injured" by pasteurization. To quote Grant et al:- "If only conventional culture on HEYM had been used to detect survivors after HTST pasteurisation in this study, the number of milk samples containing viable Myco. paratuberculosis would have been considerably underestimated".

The scientific methods used in the USDA-ARS study have also been questioned, on the following basis.

  • The USDA researchers omitted necessary details in describing their experiment, making it impossible to reproduce the research. For example, the numbers of bacteria that the USDA researchers added to milk are not definitively specified. They state:- "In these experiments, raw milk (1 to 2 liters) was inoculated with two concentrations of M. paratuberculosis (104 and 106 cells per ml) and mixed thoroughly prior to introduction into the holding vessel." However, they do not specify if "104 and 106 cells per ml" is the concentration of the inoculum or the final concentration in milk.

  • The USDA researchers studied only 2 strains of MAP. In contrast, Grant et al studied 10 and 11 strains respectively in their two experiments. Condron et al studied at least 6 strains.

  • The USDA-ARS researchers did not conduct enough control experiments to ensure that their methodology was correct, e.g. they should have run their simulation without heating the milk at all, to assure them that the MAP bacteria were not sticking to the inside of the holding tube, for example.

  • The USDA researchers based their conclusions about HTST pasteurization on the results of 4 culture samples, making it impossible to draw any statistically significant conclusions from their work. In contrast, Condron et al cultured 296 samples, and Grant et al cultured 123 and 114 samples in their two respective experiments.

  • The USDA researchers did not use standard food microbiology techniques to conduct their experiments, i.e. they did not measure D-values or Z-values.

PARA is concerned about the quality of the ARS research. If it is high quality research, and sound enough to base national dairy safety policy, then why have researchers around the world, including experienced food microbiologists, criticized the research extensively, on a number of different counts?


The most important thing to note about the dubious quality of the USDA-ARS research is that it provides a very convenient argument point which distracts attention away from the real question.

Simulation research is by definition an approximation of reality, and is thus incapable of definitively answering the real question. While the researchers argue endlessly back and forth about the parameters of simulations, the real question goes unaddressed. Arguing over "turbulent vs. laminar flow", "clumped vs. non-clumped", "frozen vs. not frozen", etc, etc, etc, is a convenient distraction from the real question -


Are the MAP bacteria present in retail supplies of dairy products (milk, cheese, infant formula, butter, cream, yogurt, ice cream, etc), viable and capable of multiplying?


The USDA-ARS research only simulated "High-Temperature Short-Time" (HTST) pasteurization. However, not all dairy products are treated with HTST pasteurization. A percentage of milk supplied by local dairies uses the "Low Temperature Holder" (LTH) pasteurization method. The LTH method is most often used to make ice-cream. Powdered milk is freeze-dried or vacuum-dried. One-third of cheese on sale in the United States is made from milk that is not pasteurized at all.

It is PARA's contention that the only research which is capable of answering the real question, is to


Test retail supplies of cows milk, cheese, butter, cream, infant formula, yoghurt, ice cream, etc to determine if the MAP bacteria in those products are alive or not.


This should have been done in 1994, when two of the world's foremost experts on MAP submitted a grant proposal to USDA New window link indicator to test retail dairy products for the presence of viable MAP bacteria!  That proposal was, of course, rejected, three times.

This critical research has been undertaken...not by ARS, and not the FDA...but by the Marshfield Clinic in Marshfield, Wisconsin.  

Marshfield Clinic Retail Milk Study

The Marshfield Clinic Retail Milk Study is testing retail supermarket milk, taken from the shelves of supermarkets, for the presence of MAP. This study is being conducted by Dr. Jay L. E. Ellingson, Director of Marshfield Laboratories Food Safety Services.  In its July/August 2002 newsletter published by the Marshfield Clinic, Dr. Ellingson states:  "Mycobacterium paratuberculosis is considered a suspect zoonotic agent because it causes Johne's disease in cattle, and some studies in the UK say it causes Crohn's disease in humans.  The question is whether people get Crohn's disease by ingesting food product derived from infected cattle." 

This is the first and only retail supermarket milk testing program for the presence of MAP ever undertaken in the United States.  Results of the study will be published in the summer of 2003.   For more information, visit the page entitled "MAP in food: The case for retail testing."


Action you can take

Please visit PARA's "How to Help" section to learn how you can get involved in creating awareness about this vital issue. 

 Contact PARA:
Paratuberculosis Awareness & Research Association, 1999-2003.