Thursday, May 13, 2010

Beef Safety In Perspective: by Ashley Mason

Beef Safety in Perspective

by Ashley Mason

This paper was used to satisfy the thesis requirements for an Honors Degree at Oklahoma State University. Ms. Mason graduates from Oklahoma State University in May, 2010 with a degree in agricultural economics and accounting. She can be reached at Her thesis advisor, Bailey Norwood, can be reached at

Food safety is a controversial agricultural topic. Food processors are doing all they can to ensure safe food -- after all, who makes money by making their customers sick? Meanwhile, the cases where consumers do get sick receive enormous attention. Some may even say these cases are exploited by groups wishing to injure the food industry. Though food is safer than at any point in history, there are approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths each year from food-borne illnesses.[1] The average American is further from the farm yet more concerned about how their food is produced. Books by authors such as Michael Pollan, interest in alternative diets such as organic foods and local-grown foods, recent efforts by the Humane Society of the United States to ban conventional livestock production techniques, and documentaries such as Food, Inc. are causing consumer anxiety over the technological changes in meat production over the last fifty years. Though consumers are concerned about many facets of modern livestock production, consumers consistently state that food safety is the most important issue.[2]

The growing interest in food safety, and more specifically food-borne illnesses, makes funding for research studies about food-borne pathogens and their behaviors more readily available. A pathogen of particular interest is Escherichia coli O157:H7. In beef, E. coli O157:H7 (hereafter, simply E. coli) is typically transmitted by contaminated cattle feces that is transferred from the animals' hides to carcasses during the harvesting process. While the pathogen does not make cattle sick, it can be deadly to humans. Research has been conducted to determine what cattle management practices may encourage the growth of E. coli, with particular emphasis on pre-harvest intervention strategies.

In order to understand what practices may increase the risk of E. coli contamination, it is important to understand the steps of the pre-harvest beef production process. In the following description, we will take a look at various studies investigating connections between E. coli contamination and management practices.

A Beef Production Primer

Cattle start their lives at a cow-calf operation. Calving typically occurs in the spring to take advantage of more favorable weather and grass availability. However, calves can be born at any time during the year. During this time, calves graze alongside their mothers in herds on pastures. Though the calves consume exclusively milk at the beginning of their life, within 3 to 8 weeks the calves will begin consuming forage as well. While nursing, approximately 83% of the calves will come into contact with E. coli. The contamination happens before weaning and without any outside animals — and thus, outside contamination — being introduced into the herd.[3] It would seem that calves are infected at a relatively early age, which may present an imposing obstacle for developing effective pathogen management practices. It may be difficult to get ahead of the E. coli contamination if calves are shedding (meaning E. coli are present in the feces) the pathogen within months of their birth. This does not imply that beef is inherently unsafe, but that the presence of pathogens is a natural and expected occurrence, one that is easily negated by with processing technologies and cooking meat thoroughly. Also, the cows in these herds are kept on pasture, with little to no grain supplement, which immediately makes the claims asserting that grain diets are the cause of E. coli contamination in beef questionable.

After the 6-10 month nursing period, the calves are weaned from their mothers. At this point they typically go to a stocker operation[4] where they may graze on young wheat, be cared for in a semiconfined production system, or be raised on one of the many other types of stocker operations until they are about 600 to 800 pounds. The transition from the cow-calf to the stocker operation entails a number of activities that may be related to E. coli contamination. Parting from their mother and being transported to a new location is stressful; this stress weakens the immune system of cattle which, as we shall see, may be related to higher E. coli levels. The calves are also introduced to new cattle, increasing the chance that E. coli will spread to calves previously free of the pathogen.

Indeed, a study conducted on 24 cattle operations at 224 sites finds that stocker calves ready to enter the feedlot are four times more likely to shed E. coli than nursing calves at the cow-calf operation.[5] One might think that the relationship between E. coli and age is caused by the fact that older calves are more likely to reside on a stocker operation than a cow-calf operation, but this is not the case. The researchers find that it is the age of the calf that causes greater E. coli shedding, not differences between the cow-calf or the stocker operation.

After the calves have gained 100-300 pounds at the stocker operation they are sold to a feedlot. The feedlot places the calves into small pens with about 100 other calves of similar age and size. The pens are large enough for the animals to move freely, but small enough that no grass will grow, and manure may accumulate to significant depths before the pens are cleaned. Almost every time the calves lie down they will come into contact with cattle manure, increasing the risk of E. coli entering the harvesting facility via the cattle-hide. In drier conditions the manure is less likely to stick on the cattle-hides, reducing the chance of carcass contamination. It is partly for this reason that most feedlots are located in dry climates, where the lack of rain reduces the extent to which the manure has a muddy composition, reducing the amount of manure brought into the harvesting facility.

Feedlots contribute towards beef value in a number of ways. The number of cow-calf operations is large and spread across substantial tracts of land. Somehow, these millions of calves from almost every region of the U.S. must find their way to a relatively small number of harvesting centers, which can typically accommodate thousands of cattle each day. Additionally, calves tend to be born in similar time periods, which implies that if these calves are raised in a similar manner they will all be ready for harvest at the same time. This is undesirable, as harvesting facilities need to operate year-round. Feedlots provide the service of coordinating the funneling of calves across space and time, so that calves are delivered year-round to the few but large harvesting facilities. By serving as a medium through which stocker calves make their way to harvesting plants, feedlots solve the coordination-across-space problem. Feedlots help manage the temporal-coordination problem by offering high prices when they have few cattle on feed, encouraging producers to remove stocker-calves from pasture earlier, and offering low prices when their cattle numbers are high.

In addition to the coordinating value feedlots provide, they feed cattle a high-grain diet which encourages better tasting meat. This ration typically contains 70-90% grain; such as ground corn, flaked corn, soybean meal, ground milo, and the like. When the cattle reach a weight of 1200-1400 they will be sold for harvest.

Some producers are capitalizing on America’s new healthy living craze by offering beef from cattle that have spent their entire lives on grass or forage based diets. They claim that this meat is lower in overall fat content, but higher in the more healthy types of fat (e.g., omega-3 fatty acids). Recently, there have been claims that grass-fed beef has lower rates of E. coli than conventionally fed beef. The Food, Inc. documentary asserted this as a fact. If only cattle by-passed the feedlot stage, gaining all their weight from forage-based diets, deaths and illness from E. coli contamination would be greatly reduced -- so feedlot critics claim. The purpose of the present research is to explore the link between the feedlot stage of beef production and E. coli. Previous research on the topic is described, as well as other research that helps us understand the extent to which dietary alterations in cattle feed can help reduce food-borne illness in humans.

Exploring the Link Between Cattle Feed and E. Coli Contamination

A study cited in Food, Inc. was conducted with three mature, nonlactating Holstein cows. The researchers varied the proportion of corn in the cattle feed and measured the amount of E. coli subsequently shed in cattle manure.[6] The theoretical rationale for this connection involves the fact that as cattle are fed increasing amounts of grain, the pH in the colon decreases -- E. coli is typically found in the colon of cattle. With a lower pH in the colon, more of the E. coli cells can potentially develop an acid resistance which would enable these cells to better survive in the human digestive tract, and hence cause more human illness. A link is detected in the study, meaning that E. coli is present in larger numbers as corn comprises a larger portion of the feed ration. Moreover, the study finds that E. coli levels can be reduced by 80% after five days on a forage-based (e.g., grass or hay) diet.

The latter result merits further discussion. Even if a switch from grain to forage diets lowers the E. coli count, abrupt changes in cattle feed can shock the digestive system, causing sickness in cattle. Illness impairs the immune system of cattle, making them more susceptible to other forms of contamination (perhaps salmonella) that could also cause human sickness. If the switch to forage-based diets can be performed over a period of time these concerns may be negated, and hence worth considering as a feedlot management strategy. Additional research is also needed to determine the degree to which carcass quality and yield would be affected by a change from a grain-based to a forage-based diet shortly before slaughter.

While this study seems shocking, one must wonder whether a sample size of three cows is sufficient to truly cause alarm. More importantly, the relationship between corn-based diets and E. coli shedding is rarely replicated in other trials. In the study performed by Renter, Sargeant, and Hungerford, they discovered that higher E. coli shedding is really the result of cattle age, and that past studies failed to control for age when exploring the link between corn and E. coli. Finally, it is worth noting that Laegreid, Elder, and Keen, who measure E. coli in calves consuming both milk and forage, tend to find E. coli in almost all cattle. All studies considered, claims that corn-based feed rations encourage E. coli contamination do not appear tenable.

Additionally, bacteria developing acid resistance in the grain-fed cow’s lower pH colon may not be as important as previously suggested. Little is understood about E. coli’s behavior. Some have found that the bacteria are able to become acid resistant relatively quickly in the human digestive system, suggesting that resistance might occur in humans regardless of whether the resistance initially occurred in the digestive tract of cattle.[7] Without a clearer understanding of how the pathogen reacts in different environments, it is difficult to determine the role that acid resistance may play in E. coli’s ability to infect humans.

A Larger View of Food Safety

The questionable link between corn in cattle feed and E. coli contamination suggests there may be better ways to improve beef consumption safety. There are a number of other management practices that can reduce E. coli contamination in human food. Even if corn-based diets encourage E. coli contamination, it might be more effective to combat the pathogen through methods other than reducing corn in the feed ration. These include antibiotics, immunization, probiotics or prebiotics in animal feed, and better beef harvesting and processing intervention activities. Irradiation can also kill pathogens residing in meat without significantly altering the composition of the meat, and only needs to be utilized to treat ground beef, as most pathogen related beef recalls involve ground beef. It is a shame that such an effective technology was given such an unfortunate name. If E. coli contaminates food by jumping from hide to carcass, better hide removal or cleaning techniques might provide the same reduction in contamination at a lower cost. However, each of these possible solutions produces its own unique set of challenges from the point of view of government regulatory agencies, producers and consumers. For example, organic beef would be unable to utilize antibiotics as a preventative practice if they wished to maintain their organic certification. Also, getting these measures accepted by various government regulatory agencies can take many years and requires substantial testing. While these strategies may help mitigate some risk of passing E. coli to consumers, most are many years away from implementation and some may be cost-prohibitive to undertake.

Consumer education may be the most cost-effective route in the fight against food borne illness. By teaching households and restaurants about proper food preparation and disposal techniques, it would be possible to put the power to end food-borne illness into the hands of consumers themselves for much lower costs than attempts to mitigate the risk earlier in the production cycle. In order to alleviate some of the fears associated with modern beef harvesting practices, we have found that tours of these modern facilities tend to make a favorable impression. They are also easy to arrange.

Though it may seem irresponsible to make decontamination of beef the responsibility of the consumer, the reader should note that consumers do not desire risk-free food consumption. Just as consumers drive cars every day, knowing that the very act entails some chance of death, millions of hamburgers are eaten everyday with the knowledge that this consumption incurs some risk. The consumer who prefers ground beef any way other than well-done knows that doing so increases the risk of illness. Daily life involves trading some amount of safety for convenience and price. The optimal risk of food illness is not zero risk. Consumers accept slightly greater risk in return for lower food prices, which consumers may use to reduce risk of harm in other ways. Spending less money for beef so that there is more money for prescription drugs may, ultimately, result in greater health. Or, they may spend the money on something they enjoy that increases risk of death even more – that is their choice. The job of food processors is to provide the level of risk that consumers want, not zero risk.

In order to find the best solution to help reduce or eliminate E. coli infections, every step of the production cycle from farm-to-fork should be carefully evaluated for potential improvement and implementation costs of recommended management practices should be considered.


It seems that food-borne illness is making the headlines more often. Because food safety is of great concern to consumers, individuals who dislike beef production for other reasons attempt to reduce beef demand by making beef appear to pose a significant health risk. It is not a coincidence that individuals who dislike the level of animal welfare, greenhouse gas emissions, and nutrient runoff associated with beef production are quick to make beef seem unsafe and unhealthy. Such individuals are often influential, and so it is important that these criticisms are addressed when they are unfounded.

While some evidence suggests that the use of corn in feedlot feed rations may be associated with higher levels of E. coli contamination, there is also evidence suggesting otherwise. When the documentary Food, Inc. discussed the study of three cows making this link, it failed to mention the other studies finding otherwise. Nor did it mention the other, potentially more effective methods of reducing food contamination. The fact that Food, Inc. reports only the studies making the feedlot stage of beef production appear undesirable suggests that it is more concerned with demonizing beef than it is with consumer education. Ignoring facts can often make for a better story, but as John Adams stated, “facts can be stubborn things.”

[1] ASAS Centennial Paper: Developments and future outlook for preharvest food safety. S. P. Oliver, D. A. Patel, T. R. Callaway, M. E. Torrence; Journal of Animal Science, Vol 87, No 1, January 2009, 419-437.

[2] Norwood, Lusk, and Prickett. October 8, 2007. “Consumers Share Views on Farm Animal Welfare.” Feedstuffs. 79(42):14-16.

[3] “Prevalence of Escherichia coli O157:H7 in range beef calves at weaning.” W.W. Laegreid, R.O. Elder, and J.E. Keen. Epidemiology and Infection. (1999), 123, 291-298.

[4] “Stocker” and “feeder” calves are two words used to describe calves that have recently been weaned. There are some distinctions between the two words. For an excellent treatment of these terms, see: Peel, D. 2003. “Beef Cattle Growing and Backgrounding Programs.” The Veterinary Clinics: Food Animal Practice. 19:365-385.

[5] “Distribution of Escherichia coli O157:H7 within and among cattle operations in pasture-base agricultural areas.” David G. Renter, DVM, PhD; Jan M. Sargeant, DVM, PhD; Laura L. Hungerford, DVM, MPH, PhD; American Journal of Veterinary Research, Vol 65, No. 10, October 2004, 1367-1376.

[6] “Grain Feeding and the Dissemination of Acid-Resistant Escherichia coli from Cattle.” Francisco Diez-Gonzalez, Todd R. Callaway, Menas G. Kizoulis, James B. Russell; Science, Vol 281, September 1998, 1666-1668. Note: although this study considers all types of E. coli, E. coli O157:H7 tends to be positively correlated with E. coli in general.

[7] “The adaptive response of Escherichia coli O157:H7 in an environment with a changing pH.” R. de Jonge, K. Takumi, W. S. Ritmeester, F. M. van Leusden; Journal of Applied Microbiology, Vol 94, 2003, 555-560.