Cattle Today

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USE OF DIRECT-FED MICROBIALS PROVIDES INNOVATIONS IN IMPROVED ANIMAL PERFORMANCE AND FOOD SAFETY

by: Stephen B. Blezinger
Ph.D., PAS

The U. S. beef cattle industry is experiencing challenges like never before and one of the most critical challenges to our industry is food safety. The American consumer and governmental agencies are requiring that beef sold in our restaurants, grocery stores and meat markets be as safe and pathogen free as possible. Meat packing companies are looking to the feedyards and the cattle producers to implement strategies to help achieve this goal.

Solving this problem will not be simple. The demand for food industry control of potentially contaminating pathogens starts, as noted, at the consumer's level, who are stating, through their buying patterns at the meat case, that they need a product in which they can have confidence. Subsequently retailers look to wholesalers and the packing companies. The packers are looking to the feedyards and the cattle producers to take the necessary steps to help reduce this problem by adopting safety standards and procedures at ALL points along the production chain. This issue is key and it will take adjustments in management procedures by all entities involved in beef production to address this issue.

The Source of the Problem

It has been well documented through scientific and medical research that the predominant organism at the root of food safety issues is Escherichia Coli (E. coli) 0157:H7, otherwise known as enterohaemorrharic E. coli. E. coli O157:H7 is one of hundreds of strains of the bacterium. Although most strains are harmless and live in the intestines of healthy humans and animals, this strain produces a powerful toxin and can cause severe illness. It also possesses other significant attributes which contribute to its' ability to cause disease. One of the more notable of its' characteristics is the size of the infectious dose: this is incredibly small in comparison with those for most other food-borne pathogens. Figures as low as two bacteria per 25g food have been quoted capable of creating a disease condition.

E. coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers. Since then, most infections have come from eating undercooked ground beef. The combination of letters and numbers in the name of the bacterium refers to the specific markers found on its surface and distinguishes it from other types of E. coli. Another pathogen of concern includes strains of Salmonella, with both E. coli and Salmonella commonly existing in the gastrointestinal tracts of cattle. These organisms are endemic and commonly found in virtually all phases of production. While they may not cause a problem in the host animal they can cause illness and even death in humans. Cattle become “infected” with this organism through exposure in their natural environment. Once the organism is ingested it travels to the intestine where is adheres to the tract lining. Meat is “contaminated” by the organism during the slaughter and processing stages when intestinal contents can come in contact with other meat surfaces and subsequently become mixed in with ground beef.

As reported by the Center for Disease Control, in humans, an E. coli infection can lead to bloody diarrhea and even kidney failure. In some persons, particularly children under 5 years of age and the elderly, the infection can also cause a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. About two to seven percent of infections lead to this complication. In the United States, hemolytic uremic syndrome is the principal cause of acute kidney failure in children, and most cases of hemolytic uremic syndrome are caused by E. coli O157:H7.

Most illness have been associated with eating undercooked, contaminated ground beef. Person-to-person contact in families and childcare centers is also an important mode of transmission. Infection can also occur after drinking raw milk and after swimming in or drinking sewage-contaminated water. The USDA Food Safety and Inspection Service (FSIS) has estimated that consumption of meat contaminated with pathogenic bacteria annually results in thousands of deaths and millions of illnesses in the U. S. alone. The government estimates the annual losses in production and medical costs may reach as high as $35 billion. The problem is well documented and identified.

Developing an Answer

Having recognized this problem, recent proactive efforts by the U.S. beef industry have resulted in recommendations of expanded research and accelerated use of intervening methodologies by industry leaders. Control and treatment techniques such as the irradiation of beef products post slaughter, use of new vaccines in cattle and direct feeding of certain additives are all under serious investigation as contributing solutions. Of these, the use of feed additives has gained significant interest, largely due to simplicity of administration. One particular group of feed additives showing significant promise in this area is probiotic or direct-fed microbial (DFM) products. The use of DFM's has grown significantly over recent years largely as a means of enhancing the health and performance of the animal. The use of bacterial-based DFM's in ruminant diets for specific applications has become widely recogized. Products of this nature often contain lactobacilli with Lactobacillus acidophilus being one of the most common. Other commonly used bacteria include various species of Bifidobacterium, Enterococcus, and Bacillus.

Most bacterial-based DFM's are beneficial because they have effects in the lower gut and not in the rumen. For example, Lactobacillus acidophilus produces lactic acid, which may lower the pH in small intestines to levels that inhibit the growth of pathogenic microbes, one of the reasons for the current interest. Early research with DFM in ruminants first involved applications for young calves fed milk, calves being weaned, or cattle being shipped. These animals, in many cases are highly stressed or had a microbial gut ecosystem that was not fully mature. Young cattle have immature digestive tracts that are obviously more prone to upset by pathogenic bacteria. Cattle that are shipped are often on limited feed and water for prolonged periods of time during transit. During these periods microbial populations may decrease in numbers thus resulting in digestive tracts that are in less than optimal condition. Large doses of beneficial organisms were thought to re-colonize a stressed intestinal environment and return gut function to normal.

There have been several hypotheses put forth to explain the usefulness of DFM's. One of the most common explanations for improved animal health or production suggests that the addition of beneficial bacteria prevent the colonization of pathogens in the lower gut by competing for space and nutrients. Production of antimicrobial end products such as acids and antibiotics has also been discussed. Some of the proposed mechanisms for how DFM's work include:

*Production of antibacterial compounds (acids, antibiotics).

*Competition with undesirable organisms for space and/or nutrients in the digestive tract.

*Production of nutrients (e.g. amino acids, vitamins) or other growth factors which stimulate growth and reproduction of other microorganisms in the digestive tract.

*Production and/or stimulation of enzymes.

*Breakdown and/or detoxification of undesirable compounds

*Stimulation of the immune system in the host animal.

In the past most DFM feeding applications have been during stress periods, especially during periods starting at receiving and for a period shortly thereafter. Research at several major universities is showing a benefit to ongoing feeding of bacterial cultures as a means of improving intakes, stabilizing intakes and improving average daily gains. In light of the current concern over food safety the usefulness of these products in reducing pathogen levels in beef cattle is actively being researched. Results are very promising. In a recent study by Brashears and Galyean, (2002) the feeding of several strains of beneficial bacteria, including Lactobacillus acidophilus showed a significant reduction (P<.05) in the incidence of E. Coli O157:H7 in the feces of finishing cattle. Ongoing work has shown that levels of E. coli increases in cattle during the finishing period. Feeding of specific strains of beneficial bacteria has shown to reduce the levels of pathogenic proliferation.

Studies of this nature are eliciting positive responses from a number of meat packers. Many packers are making strong recommendations to their supplying feedyards to feed probiotics to help with this issue. Their position is that if the level of E. coli entering the facility via the animal is reduced, their ability to further reduce contamination is vastly improved.

The research into this area is ongoing by universities and a number of companies. In particular several bacterial strains developed by Lallemand Animal Nutrition (LAN; Milwaukee, WI) have shown significant results in reducing the concentrations of E. coli O157:H7 and Salmonella via a process known as competitive exclusion. Competitive exclusion is a process by which beneficial bacteria are used to colonize the lining of the intestinal walls, reducing the area available for attachment by pathogenic microbes. The results so far confirm earlier theories that part of the effect noted through the feeding of beneficial bacteria results from this reduction in the area of the intestinal lining available to the pathogen for attachment.

Certain, specific strains of Lactobacilli and Propionibacterium developed by LAN have proven effective at reducing the numbers of these pathogens under different environmental conditions. Probiotic research has shown the effectiveness of gut colonization of beneficial bacteria in reducing pathogenic populations through competitive exclusion of these harmful organisms. In recent in vitro collaborative work by LAN and AgTech (Waukesha, WI. A 15-year-old biotech research company), it was found that several bacterial strains were highly effective in inhibiting the growth and development of strains of Salmonella and E. coli including E. coli O157:H7. The results indicate that in particular the BG2FO4 strain of Lactobacillus Acidophilus was very effective in inhibiting all strains of pathogenic E. coli tested. It is also important to note that the inhibition was a result, not only of competitive exclusion but also as a result of the action of extracellular bacteriocins produced by the Lactobacillus. The results also indicated inhibition of several strains of Salmonella. As a result, it was concluded that Lactobacillus Acidophilus BG2FO4 exhibits a high degree of pathogen oriented anti-microbial activity and is an excellent choice for use in beef cattle for this purpose.

Conclusions

Research has and continues to reveal useful methodologies for the control of pathogenic bacterial populations in finishing beef cattle. Through a combination of internal and external research projects, LAN is providing solutions to the consumer demand for safer beef products and is establishing through research and application its' place in the beef industry. The tremendous body of knowledge in this exciting and productive field of study is resulting in microbial product lines that are proving highly effective in enhancing cattle health and performance.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached at Route 4 Box 89, Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at sblez@peoplescom.net.

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