Safety Practices

Reducing Bacterial Load

Abstracted by Eldon J. Hans, Past BQA Coordinator, ICA

Bacteria in Cattle

The following are important findings of Sofos, et.al of Colorado State University in a March 1998 response to a request from the NCBA BQA Advisory Board:

I. Items that should be considered prior to conducting studies of preslaughter pathogen interventions are as follows:

a.) Live animals cannot be sterile because the environment to which animals are exposed isn’t sterile.

b.) Cleaner animals would reduce the odds of pathogen presence in/on carcasses, cuts and endproducts.

c.) Even if animals carry the least contamination possible, that’s not the whole story because carcasses, cuts and endproducts can be subsequently contaminated.

d.) No Critical Control Point (CCP; kill step) will likely be identified for preharvest use on live animals.

e.) Good Management Practices or Good Production Practices (GMPs/GPPs) would be helpful for presenting cleaner animals for slaughter.

f.) In a farm-to-table food safety approach, GMPs/GPPs vs. Poor Management Practices or Poor Production Practices (PMPs/PPPs) can be cumulative.

g.) NCBA food safety research studies have concentrated on slaughter/post-slaughter microbiological interventions because that is where meat is exposed to environmental contamination.

II. Facts currently known about E. coli O157:H7 preharvest are the following:3

a.) Is distributed throughout the United States.

b.) Occurs in dairy, feedlot and range cattle.

c.) Does not cause clinical symptoms in carrier animals.

d.) Can be transmitted among cattle.

e.) Persists on farms for at least two years.

f.) Is shed variably among herds.

g.) Is shed intermittently by individuals.

h.) Is shed more often in warm weather.

i.) Colonizes in deer, sheep, horses, dogs, flies and birds.

j.) Has no host or long-term reservoir that has been identified.

k.) Is present in multiple sources on the farm.

l.) Occurs as the same strain, on many sites, in many states; birds could be responsible for its widespread distribution.

m.) Prevalence is not related to new-animal introduction into a herd.

n.) Prevalence is not related to spreading manure on pastures or rangelands.

III. Knowledge of prevalence of E. coli O157:H7 preharvest includes the following information:

a.) Presence in Feces: Individuals, 0 to 5 percent; cows, up to 19 percent; herds 1 percent to 75 percent; higher in young than in old animals; feedlot cattle, 1.6 percent; among feedlots, 63 percent.

b.) Causes of Increase in the Feedlot: On feed, <20 days; entry, <700 lb.

c.) Has no Effect in the Feedlot: Animal health; pen density; antibiotics, probiotics; urea.

d.) Things Worthy of Study: Coccidiostats; drinking water; not in feed ingredients but in rations in feedbunks; moistened feed; propionic acid.

IV. Current knowledge of prevalence of Salmonella preharvest includes the following information:

a.) Found in 5.5 percent of fresh fecal pat samples in feedlot pens.

b.) Found in 38 percent of feedlots (in fecal pats).

c.) Found in feed ingredients and in rations in feedbunks.

d.) Shed more often as cattle time-on-feed increases.

e.) Prevalence is highly variable within feedlots.

f.) Prevalence is higher during warm months.

g.) Serotypes causing human illness are found infrequently.

In October 1998, the Washington State University reported a study which examined the prevalence of E. coli O157:H7 in feedlot cattle sampled at slaughter plants. Hair and fecal samples from 240 cattle at four slaughter plants were collected immediately post-stunning.

Fecal samples were positive for E. coli O157:H7 at a rate of 5.8 percent, while only 1.7 percent of hide samples were positive samples collected from holding pens at one of the slaughter plants, where 15 out of 919 samples were found positive (1.6 percent) for E. coli O157:H7.

No cattle were positive for both hair and fecal samples.

This suggests that fecal testing of preharvest cattle is not a dependable way to determine which cattle have the greatest potential for contaminating carcasses with E. coli O157:H7. Although hide incidence is at a lower rate, it has been shown to be a more common source of bacterial contamination. By providing a cleaner holding environment for cattle, it may be possible to minimize hide contamination regardless of presence of E. coli O157:H7 in feces.