United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health April 2013 

_________________________________________________________________________________________________________________________ 

Preharvest Food Safety 

Practices in U.S. Feedlots, 2011 

Pathogens that cause foodborne illness, such as 

Salmonella and E. coli O157:H7, can be found in cattle 

feces and on hides. In some cases, beef has been 

implicated as the source of human illness caused by 

foodborne pathogens. USDA’s Food Safety and 

Inspection Service (FSIS) monitors the safety of meat at 

slaughter through the Hazard Analysis and Critical 

Control Points (HACCP) system. Because of the HACCP 

system, many new advances and decontamination 

technologies have been developed to improve the safety 

of meat. These in-plant interventions have been highly 

effective at reducing the occurrence of pathogens on 

carcasses such as E. coli O157:H7. However, these 

interventions do not prevent all foodborne pathogens. If 

the load of foodborne pathogens in cattle entering the 

plant is large, there is greater likelihood of carcass 

contamination at slaughter.a

 

Controlling potential foodborne pathogens at the 

farm level before cattle go to slaughter might decrease 

pathogen loads and augment in-plant interventions to 

reduce or eliminate the risk of contamination. FSIS 

recognizes the importance of preharvest practices in 

protecting food safety and recommends that slaughter 

establishments receive their cattle from beef producers 

that implement one or more documented preharvest 

practices to reduce fecal shedding of foodborne 

pathogens.b

 However, at present, there are a number of 

impediments to widespread implementation of 

preharvest practices designed to reduce foodborne 

pathogens including: 1) limited data on the effectiveness 

of available practices, 2) lack of financial incentives, and 

3) limited numbers of products or processes approved 

by regulatory authorities. 

NAHMS 2011 Feedlot study 

The U.S. Department of Agriculture’s National 

Animal Health Monitoring System (NAHMS) conducted 

the Feedlot 2011 study, an in-depth look at large 

feedlots (1,000 or more head capacity) in 12 States1

 

and small feedlots (fewer than 1,000 head capacity) in 

13 States.2

 Some of the results presented in this 

information sheet reflect only large feedlots, while others 

include both large and small feedlots. 

 

1

 Arizona, California, Colorado, Idaho, Iowa, Kansas, Nebraska, New 

Mexico, Oklahoma, South Dakota, Texas, Washington. 

2

 Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, 

Nebraska, Ohio, Pennsylvania, South Dakota, Texas, Wisconsin.

Large feedlots accounted for 82.1 percent of the 

January 1, 2011, inventory of feedlot cattle in all U.S. 

feedlots but only 2.8 percent of all feedlots. Small 

feedlots accounted for 16.0 percent of the inventory on 

all U.S. feedlots and 92.9 percent of all U.S. farms with 

cattle on feed. 

Vaccines 

Current research suggests that vaccines can reduce 

fecal shedding of foodborne pathogens in cattle.b

 In the 

United States, one E. coli O157 vaccine has a 

conditional license for use in cattle, and several 

Salmonella vaccines are licensed (or have a conditional 

license) for use in cattle. At this time, a low percentage 

of feedlots vaccinate at least some cattle for E. coli or 

Salmonella (table 1). 

Table 1. Percentage of feedlots that gave any cattle 

placed on feed the following vaccines, by feedlot 

capacity 

 Percent Feedlots 

Feedlot capacity (number head)

Vaccine 

1,000–

7,999 

8,000 or 

more 

All feedlots 

(1,000 or more)

Salmonella (e.g., 

Salmonella

Newport SRP®)

4.9 10.1 6.5 

E. coli (e.g., 

Epitopix SRP® 

or Econiche®) 

1.4 4.6 2.4 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Monitoring foodborne pathogens 

A low percentage of feedlots monitored (e.g., 

through testing) for either E. coli O157 or Salmonella

(table 2). 

Table 2. Percentage of feedlots monitoring the 

following food safety pathogens in cattle, by feedlot 

capacity 

Percent Feedlots 

Feedlot capacity (number head)

Food safety 

pathogen 1,000–7,999 

8,000 or 

more 

All feedlots

(1,000 or 

more)

E. coli O157 5.9 13.2 8.0 

Salmonella 5.3 10.7 6.9 

Preharvest food safety prevention practices in 

feed or water 

Feed or water management practices have been 

examined in research studies to investigate their effect 

on the prevalence of cattle shedding pathogens. Table 3 

reports the frequency of use of some of these practices 

by U.S. feedlots. Many are infrequently used in feedlots, 

especially among those with capacity of fewer than 

1,000 head. Because most past research has focused 

on E. coli O157, the description of effects below will be 

limited to this pathogen. This is not an exhaustive list of 

practices available for prevention of foodborne 

pathogens. 

The management practices in table 3 have varying 

effects on the presence of E. coli O157. For example, in 

most but not all studies, feeding distiller’s grains has 

been shown to increase E. coli O157 shedding in cattle.b

In addition, a number of studies have shown that fasting 

prior to slaughter increases O157 shedding in cattle.b

Most research shows that treating water with chlorine 

has a negligible effect on O157 shedding.a

 The use of 

ionophores has had inconclusive results on O157 

shedding, but there may be an interaction between 

ionophore use and ration components.c

 While some 

research has shown a decrease in O157 shedding 

following a change from a high grain ration to a high 

forage ration prior to slaughter, as a whole results are 

inconclusive.c

 In addition, this practice has a detrimental 

effect on performance (body weight) and is not practical. 

The addition of seaweed extract to rations has been 

evaluated, but the effect on O157 shedding is 

insufficient to recommend its use.d

 As a whole, results to 

date indicate that beta-agonists in rations have minimal 

effects on O157 shedding.c

 Of the management 

practices in table 3, probiotics in rations may have the 

most promise at reducing O157 shedding, but not all 

probiotics are equally effective.a None of these practices 

appears to be effective alone at reducing the prevalence 

of foodborne pathogens, but there is potential for 

combinations of practices (e.g., vaccines and probiotics) 

to control these pathogens. However, these 

combinations of practices have yet to be fully evaluated. 

Table 3. Percentage of feedlots by management 

practice and by feedlot capacity 

 Percent Feedlots 

Feedlot capacity 

(number head)

Management practice 1–999 

1,000 or 

more 

Fed distiller grains as 

part of the ration 25.6 90.5 

Fasted prior to 

transportation to slaughter 11.3 15.9 

Provided water that 

was treated with chlorine 7.9 8.2 

Gave an ionophore, such as 

Rumensin® or Cattlyst® 28.7 90.5 

Switched from a high grain 

ration to a primarily hay 

ration at finish 

7.3 3.3 

Fed seaweed extract 

(e.g., Tasco-14®) prior 

to slaughter 

0.0 0.6 

Fed a beta-agonist 

(OptaFlexx® or ractopamine) 3.9 36.9 

Fed a beta-agonist (Zilmax® 

or zilpaterol) 1.6 10.6 

Fed probiotics in feed 

(e.g., Lactobacillius 

acidophilus, Bovamine®) 

8.3 28.5 

Summary 

Preharvest practices specifically targeted toward 

reducing shedding of foodborne pathogens (e.g., 

vaccines, seaweed extract, chlorine treatment of water, 

or switching from grain to hay diets) are not commonly 

practiced in U.S. feedlots. Practices that have additional 

benefits other than the potential to reduce foodborne 

pathogens (e.g., feeding of ionophores or probiotics) are 

more commonly practiced, especially in large feedlots. 

References 

a. Loneragan GH, Brashears MM. 2005. Pre-harvest interventions to 

reduce carriage of E. coli O157 by harvest-ready feedlot cattle. Meat 

Science 71:72–78. 

b. USDA–Food Safety and Inspection Service. 2010, Pre-harvest 

management controls and intervention options for reducing 

Escherichia coli O157:H7 shedding in cattle. Available at: 

http://www.fsis.usda.gov/PDF/Reducing_Ecoli_Shedding_In_Cattle_05

10.pdf 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

c. Callaway TR, Edrington TS, Loneragan GH, Carr MA, Nisbet DJ. 

2013. Shiga-toxin-producing Escherichia coli (STEC) ecology in cattle 

and management based options for reducing fecal shedding. 

Agriculture, Food & Analytical Bacteriology. 3:39–69. 

d. Beef Industry Food Safety Council. Production best practices (PBP) 

to aid in the control of foodborne pathogens in groups of cattle. 

Available at: 

http://www.bifsco.org/CMDocs/BIFSCO/Production%20Best%20Practi

ces.pdf 

_____________________________ 

For more information, contact: 

USDA–APHIS–VS–CEAH–NAHMS 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

http://nahms.aphis.usda.gov

#667.0213 

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