Recently, Cornell University issued a press release to the consumer media promoting a research trial on E. coli. It contained sweeping, categorical statements that received big play.
Originally published in Science magazine, the research itself is interesting. The editorial comment in the press release is shocking, however, because theory is presented as fact.
The headline theory is that E. coli 1057:H7 can be eliminated by feeding hay to feedlot cattle five days before slaughter. The problem is that none of the cattle used in the study (all dairy cows) tested positive for 0157:H7. The researchers extrapolated this conclusion based on another one of their theories: that pathogenic E. coli can only come from ruminants fed grain rations.
Misleading By Omission Most distressing, the editorial comment implies that cattle are responsible for all 0157:H7 infections. Ground beef actually makes up a small portion of total infections. Fruits and vegetables (eaten raw) make up a much larger percentage.
The authors implicitly answer this by stating that manure is sometimes used to fertilize vegetables, totally ignoring the well-known human contamination route (more later).
Specifically, the researchers claim that the acidic nature of the human stomach can destroy E. coli. However, if the E. coli develop in a grain-fed ruminant, the acidic nature of the fermentation products makes the E. coli acid-tolerant (and able to survive the human stomach), they say.
The researchers devised a laboratory experiment to "prove" this theory. In the opinion of most scientists, however, "in vitro" (test tube) analysis should never be considered final proof. The "in vivo" (real) world can be quite different.
In this case, there is a lot of epidemiological evidence to the contrary. As mentioned, this theory overlooks the well-known fact that human to human contact is a common source of many types of pathogenic E. coli.
The Human Factor Indeed, in Third World countries, the most common source of pathological E. coli infections is contaminated water - water contaminated with human waste (a common cause of dysentery). With respect to E. coli 0157:H7, human to human contact is also well known to be a source of infection. Ladies have contracted it changing diapers. Children at day care centers have become infected through contact with a "carrier" child.
When I eat a hamburger, I don't worry about the meat (if it's well cooked), but the lettuce. OSHA requires farm workers to be provided with portable toilets and hand washing facilities. While we can be certain the potties are being used, we cannot be sure about the wash basins.
The Center for Disease Control has listed farm and food workers as a potential for contamination. This is the greatest worry - foods that cannot be cooked. (Lettuce is reported as the leading source of infections by E. coli 0157:H7).
The Acid Tolerance Theory Aside from the well-known fact that humans can be carriers, a little knowledge of ruminant nutrition and common sense would question this "acid tolerance" theory. While rumen fluid from a feedlot ration will be about pH 5.5 (vs. 6.5 for a hay ration), the human stomach is a pH 2.0.
The pH scale is logarithmic, meaning the acidity in rumen fluid from grain rations will be about 10 times more acid than forage rations, but it will be no less than 1,000 times less acid than the human stomach.
It is hard to believe the relatively moderate differences in pH for various rations can be the source of all pathogenic E. coli.
If there is an area of this research that is assuredly correct, it's that grain that bypasses to the large intestine would support larger bacterial populations. However, an all-hay diet would greatly increase the likelihood of fecal contamination (on the carcass). Therefore, it is vital we know if the "acid tolerance" theory is correct.
The Effects Of Hay Feeding As for the economic and practical aspects of feeding hay the last five days before slaughter, could we do it? The only unknown at this point is dark cutters. My gut feeling is that it would not be much of a problem, but there is enough concern in the industry that this should be researched.
In terms of cost, we would lose about 111/42-2 lbs. of gain/day for the five days. There would also be more "fill" on the cattle, thereby increasing trucking costs slightly. The net cost (excluding any potential problem with dark cutters) would run somewhere on the order of about $10/hd.
Certainly the cost would be reasonable. The real question is "does this hay feeding work?" We don't know. This study is little more than speculation. But even if works, there are practical considerations to ponder.
Most packers contend E. coli contamination comes not from fecal matter in the digestive tract, but mud and manure on the hide. Most contamination occurs when the hide is stripped.
Switching to hay would increase the volume of manure by 50 to 150% and make it much more liquid. Defecation would be more frequent, and with high-quality hay can be "projectile" in nature. The result is cattle confined closely before slaughter would have hides much more soiled with manure.
Therefore, while the "science" of this study is in question, there are some very serious practical questions as well.