Corn is a staple in conventional beef cattle diets. It is fed whole or processed in a variety of ways, including steam flaked, dry rolled, and high moisture.
The method used to process corn is determined by animal type, geographical location, and economics.
In the upper Midwest, it is often fed to cattle in the form of dry rolled corn or high moisture corn, while in the Southern and Western states it is often fed as steam flaked corn when used in feedlot diets.
Each type of corn processing method has its own advantages and disadvantages. Whole corn, for instance, is harder to digest, but inexpensive to produce, and easy to store.
Dry rolled corn, on the other hand, is slightly more expensive to produce, but it is more highly digested when consumed.
Finally, steam flaking corn is one of the most expensive processing methods, and it requires the highest capital investment. It does, however, produce the most digestible corn product of the three mentioned.
In the past, when it came down to choice of processed corn, there were two main factors that needed to be considered. The first was the cost to process it. This would include drying cost, corn processing cost, and facility cost, among other things.
The second consideration was the digestibility of the corn. A more heavily processed corn is generally more digestible. This means that the animal will utilize more of the corn kernel and obtain a greater amount of nutrients from the corn.
A less processed corn kernel will not be fully digested and will thus be excreted as waste. It was up to the producer to determine what was more economic: a low processing cost with a higher nutrient waste, or a greater use of nutrient with a higher processing cost.
Now, however, these two considerations are not the only factors that a producer must account for when choosing corn.
With the ever increasing concern that beef may become contaminated with Escherichia coli O157:H7 during cattle harvest, it behooves producers to contribute to reducing the prevalence of E. coli O157:H7 in cattle.
This has led to a great deal of investigation into what causes an increase or decrease in E. coli O157:H7 prevalence. Diet, environment, and production practices have all been considered and examined for their effect on E. coli O157:H7 prevalence in the herd.
And the result of all the research was the discovery that the type of method used to process corn may have an effect on E. coli O157:H7 prevalence in the herd. It has been found in a host of studies that there is a distinct link between corn processing method and E. coli O157:H7 prevalence in a beef cattle herd.
Of the methods examined, a majority of studies found that feeding steam flaked corn resulted in a greater amount of E. coli O157:H7 fecal shedding by beef cattle than when feeding dry rolled corn.
Data suggests that E. coli O157:H7, a particularly virulent and foodborne form of E. coli, colonizes and grows in the hindgut of ruminants.
The hindgut is likely more hospitable for E. coli O157:H7, as suggested by Fox et al., due to its higher pH, lower volatile fatty acid production, and lack of ciliated protozoa. Thus, changes to the hindgut environment will have a greater impact on E. coli O157:H7 prevalence than changes to the rumen environment.
What does all of this have to do with the type of corn? Well a more processed corn, like steam flaked corn, will be mostly digested in the rumen. That means that the corn will alter the rumen environment, changing pH, volatile fatty acid production, and so on. A less processed corn, such as dry rolled corn, will not be as fully digested in the rumen. Thus, it will have less of an effect on ruminal pH, volatile fatty acid production, etc.
However, the dry rolled corn will proceed into the lower gastrointestinal tract where it will continue to ferment in the hindgut. This will lead to a change in pH and volatile fatty acids in the cecum and colon. These environmental changes may consequently have an effect on E. coli O157:H7 survival in the lower gastrointestinal tract.
It will, in theory, become more difficult for the E. coli O157:H7 to survive and flourish, leading to a reduction of E. coli O157:H7 numbers in the tract, as well as the numbers being excreted.
As a beef cattle producer, this information can be used to reduce E. coli O157:H7. By feeding a diet with a less processed corn source (i.e. dry rolled corn, whole corn, etc.) the cattle digestive tract may be altered in a way that will make it more difficult for E. coli O157:H7 to survive in individual animals, thereby reducing overall E. coli O157:H7 prevalence in the herd.
It should be noted, however, that a recent UMN study found no correlation between E. coli O157:H7 and the type of corn processing.
These contrasting research results suggest that there are situations where environmental factors may have a greater impact on E. coli O157:H7 prevalence than the type of processed corn used.
As public concern for E. coli O157:H7 contamination of food continually increases, it is becoming more and more important for producers and processers to reduce E. coli O157:H7 contamination risk. Altering the cattle diet may be one method of control; however, many factors likely contribute to E. coli O157:H7 prevalence in cattle herds and a producer should work closely with both their nutritionist and veterinarian to control E. coli O157:H7.
For more information regarding beef feedlot nutrition or any other beef-related topic, please visit the U of M Beef Team website at: http://www.extension.umn.edu/beef.