Research on Hay Feeding Effects on E. coli Shows Promise, Yields Questions

Livestock Update, November 1998

John Hall, Extension Animal Scientist, Beef, Animal and Poultry Sciences, Virginia Tech

In a recent article in the journal Science, researchers from the USDA Agriculture Research Service at Cornell reported that shifting cattle from a high grain diet to a predominately hay diet resulted in a significant reduction in acid resistant E. coli concentrations in the large intestine. The results they reported raised some interesting possibilities as well as some additional questions. Agents need to be aware of some of the following facts in regard to this article when answering questions posed by the public in response to this highly publicized research.

In reviewing both the paper and analyses of the paper, I found:

1. Switching to the hay diet did result in significant reductions in acid resistant E. coli bacteria in the gut of cattle.
2. The researchers did not differentiate between type of E. coli, specifically they did not measure amounts of O157:H7
3. Some reviewers of the article were not particularly impressed with the methods used to determine bacterial numbers and acid resistance. They felt more refined methods should be used.
4. All cattle were mature dairy cattle and small numbers were used.
5. Adoption of this method by the feedlot industry would require massive shifts in the nutrition and marketing of finished cattle. Substantial increases in hay inventory and grinding for use by finished cattle would drive cost of production higher. Once cattle were put on the hay diet, there would be no turning back -- cattle would have to be marketed in 5 to 7 days. Therefore, cattle could not easily be held due to price or weather difficulties.
6. We have no data on the effects of switching to a hay diet for 5 days on carcass quality and palatability characteristics of the carcass.

In summary, my response to the general public's inquiries about this research are that it looks promising, but we need more information from large scale studies from Universities set up to do large scale feedlot research such as Iowa State, South Dakota State, University of Nebraska, University of Oklahoma and Texas A&M. Information on the types of bacteria that decrease, carcass quality and palatability are needed. In addition, before a large-scale change in the industry occurs, we need to know if this will reduce pathogen levels below safety methods already in place at processing plants and the cost to the feedlot sector.

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