This study was designed to discover relationships between characteristics of feedlot pens and the percentage of cattle shedding Escherichia coli O157:H7. Twenty-nine pens from five Midwestern feedlots were each sampled once between June and September, 1999. Feces were collected from all cattle in each pen. E. coli O157:H7 was isolated from the feces of 714 of 3162 cattle tested (23%), including at least one animal from each of the 29 pens. Pen prevalence did not differ between feedyards, but did vary widely within feedyards. Muddy pens were more likely to have a higher pen prevalence than normal pens

Blackford, Mark

Gray, Jeff

Hungerford, Laura

Klopfenstein, Terry J.

Milton, Todd

Moxley, Rodney A.

Smith, David R.

Younts, Spring

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department January 2001 The Relationship of the Characteristics of Feedlot Pens to the Percentage of Cattle Shedding Escherichia coli O157:H7 Within the Pen David R. Smith University of Nebraska-Lincoln, dsmith8@unl.edu Mark Blackford University of Nebraska-Lincoln Spring Younts University of Nebraska-Lincoln Rodney A. Moxley University of Nebraska-Lincoln, rmoxley1@unl.edu Jeff Gray University of Nebraska-Lincoln See next page for additional authors Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Smith, David R.; Blackford, Mark; Younts, Spring; Moxley, Rodney A.; Gray, Jeff; Hungerford, Laura; Milton, Todd; and Klopfenstein, Terry J., "The Relationship of the Characteristics of Feedlot Pens to the Percentage of Cattle Shedding Escherichia coli O157:H7 Within the Pen" (2001). Nebraska Beef Cattle Reports. 321. https://digitalcommons.unl.edu/animalscinbcr/321 This Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Authors David R. Smith, Mark Blackford, Spring Younts, Rodney A. Moxley, Jeff Gray, Laura Hungerford, Todd Milton, and Terry J. Klopfenstein This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/animalscinbcr/321 Page 81 — 2001 Nebraska Beef Reportrelief from heat stress conditions.Although RH over the mound isincreased, the decrease in microclimatetemperature associated with waterapplication results in either no effect ora concomitant lowering of THI. Thedecrease in temperature is significant inallowing for a maximization of the heatgradient between animal and environ-ment in order to allow greater heat dissi-pation. Our performance and TT datasuggest preventing cattle from gettingtoo hot during the day by providingexternal cooling in the morning is supe-rior to providing external cooling in theafternoon. However, providing externalcooling in the afternoon tended toenhance intake during very hot envir-onmental conditions.1Shane Davis, graduate student, AnimalScience; Terry Mader, professor, Animal Science;Wanda Cerkoney, research technician.Figure 5. Effect of water application to feedlot mounds on tympanic temperature of steers.abValues within a time with different superscripts differ (P < .05).106105104103102101100Temperature, oFCONAMPM080010001200140016001800200022002400020004000600Time of day, haabaaaaaaaaabaaaaaaaaaaaaaaaa aaaabbbbbbbbbbbbbbbThe Relationship of the Characteristics of FeedlotPens to the Percentage of Cattle SheddingEscherichia coli O157:H7 Within the Pen(Continued on next page)David SmithMark BlackfordSpring YountsRodney MoxleyJeff GrayLaura HungerfordTodd MiltonTerry Klopfenstein1The food-borne pathogenEscherichia coli O157:H7 wascommonly found in pens of feed-lot cattle, and the percentage ofcattle shedding the organism mayhave been influenced by the penenvironment.SummaryThis study was designed to discoverrelationships between characteristicsof feedlot pens and the percentage ofcattle shedding Escherichia coliO157:H7. Twenty-nine pens from fiveMidwestern feedlots were each sampledonce between June and September,1999. Feces were collected from allcattle in each pen. E. coli O157:H7was isolated from the feces of 714 of3162 cattle tested (23%), including atleast one animal from each of the 29pens. Pen prevalence did not differbetween feedyards, but did varywidely within feedyards. Muddy penswere more likely to have a higherpen prevalence than normal pens.IntroductionEscherichia coli bacteria are com-monly found as normal inhabitants ofthe intestinal tracts of humans andanimals. Unfortunately, some strainsincluding E. coli O157:H7, though gen-erally harmless for cattle, carry traitsthat allow them to cause serious food-borne disease in humans.Many segments of the food indus-try have adopted the principles ofhazard-analysis-critical-control-points(HACCP) to minimize the likelihoodthat food will be contaminated withpotentially dangerous pathogens.Unfortunately, there is insufficientknowledge of the epidemiology and2001 Nebraska Beef Report — Page 82ecology of E. coli O157:H7 to designand implement HACCP-based foodsafety programs in cattle feedyards.Cattle in feedlots rarely are handledas individuals. Most conceivable con-trol points for reducing human food-borne pathogens in feedlot cattle wouldbe directed towards pens of cattle.Therefore, epidemiologic studies withthe objective of identifying manage-able factors (control points) to reducehuman food-borne pathogens in thefeedlot should relate the characteristicsand pathogen status of managed groupsof cattle (pens), rather than characteris-tics of cattle as individuals. The objec-tive of this study was to describe thepercentage of cattle shedding E. coliO157:H7 in feces within Midwesternfeedlot pens and to identify potentialrisk factors for pen prevalence.ProcedureStudy designThe study design was cross-sectionalobservational at the level of the feedyardpen. The percentage of cattle within apen shedding detectable levels of E. coliO157:H7 was described and comparedto concurrent characteristics of thefeedlot pen relating to the cattle andthe pen environment. Approximately 30g of feces was collected from the rec-tums of all cattle within each pen whilethey were restrained in a handling chutefor routine management procedures(re-implanting). Concurrent sampleswere collected of water from water tanks,and partially consumed feed fromfeedbunks of the same pens. Concurrentinformation was collected aboutcharacteristics of the pen that may berisk factors for the prevalence of cattleshedding E. coli O157:H7. These fac-tors included number of cattle, days onfeed, average body weight, class and sexof cattle, culture results from water orfeed, water-tank temperature and pH,and subjective assessments of pencondition and water-tank cleanliness.Source of cattleFive feedyards, typical of commer-cial feedlots in the region, were asked tovoluntarily participate in the study. Theone time cattle capacity in these feedyardsranged from 3,000 to 12,000 head;approximately 40,000 head collectivelyin pens of 50 to 300 head. Pens wereopen-dirt lots, maintained by scraping,typically once per month. The feedlotsinvolved in this study fed primarilydry-rolled corn, high-moisture corn,wet corn gluten feed, wet distillersgrains, alfalfa hay, corn silage, andother byproducts. Cattle pens wereselected from the 5 commercial feed-yards at the time of routine re-process-ing. Pens were bypassed, or pens withfewer cattle were chosen for sampling,during weeks when more pens wereavailable than could be managed by theculturing capacity of the laboratories.Sampled pens ranged from 36 to 231(median 107) cattle. At sampling, cattlehad been in the feedyards 19 to 108(median 51) days and the mean bodyweight per pen ranged from 764 to1175 lbs (median 930 lbs).MicrobiologyCulture methods were specific to thetype of sample but included selectiveenrichment and immunomagneticseparation. Isolates were confirmed bystandard methods including PCR.Methods for recovery of E. coliO157:H7 from feces were modificationsof those recently reported (Laegreid etal., 1999. Epidemiol Infect. pp291-298).Statistical methodsThe dependent variable was the pen-prevalence of E. coli O157:H7 definedas the percentage of cattle within a penfrom which the organism was isolatedfrom feces. The correlation between themagnitude of pen-prevalence of E. coliTable 1. Continuous or ordinal variables describing 29 feedlot pens from 5 Midwestern USfeedyards and the correlation of the variable to the percentage of cattle within pens foundshedding Escherichia coli O157:H7 in the feces.Range of values Spearman’s rankVariable (Median) correlation coefficient P-valuePen size 336-231 (107) r = 0.08 0.67Days in the feedyard 19-108 (51) r = -0.21 0.28Average body weight 764-1175 (930) r = 0.00 1.00Temperature of water in tank 53.7-67.5 (61.1) r = -0.17 0.37pH of water in tank 6.2-8.2 (7.2) r = -0.10 0.62Cleanliness of water in tank 1-5 (3) r = -0.02 0.93pH of feed in bunk 4.2-7.3 (4.8) r = -0.11 0.55Figure 1. Percentage of cattle shedding detectable Escherichia coli O157:H7 in each of 29 pens offeedlot cattle in five Midwestern feedyards. Prevalence levels of fecal-shedding forindividual pens are represented by bars arranged in order of increasing prevalence byfeedyards of origin.9080706050403020100Percent of pen shedding O157:H71 1 1 1 1 2 2 2 2 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5Feedlot codePage 83 — 2001 Nebraska Beef ReportO157:H7 (rank order of pen-prevalence)and variables representing pen charac-teristics which were at least ordinal wastested using Spearman’s rank correla-tion. Association of the magnitude ofpen-prevalence with categorical vari-ables was tested using non-parametricmethods.ResultsE. coli O157:H7 was isolated fromthe feces of 714 of 3162 cattle tested(23%), including at least one animalfrom each of the 29 pens. The pen preva-lence of cattle shedding detectablelevels of the organism ranged from 0.7%to 79.8% (median 17.1%). Feedyardsdid not differ by pen prevalence (Kruskal-Wallis P=0.81); however, within eachfeedyard the pen prevalence differedwidely (chi square P<0.001; Figure 1).E. coli O157:H7 was recovered fromthe water tanks of seven pens and thefeed from the bunk of one pen. Penprevalence was not associated withrecovery of the agent from feed(Wilcoxon rank sums P=0.31), or water(Wilcoxon rank sums P=0.15). Penprevalence was not correlated with thetemperature, pH, or cleanliness of waterfrom the water tanks, or pH of the feed,number of cattle, mean body weight ornumber of days in the feedyard (Table1).The condition of the pen surface,subjectively evaluated as dry, normal, orwet, was associated with the level of penprevalence (Kruskal-Wallis P<0.05; Fig-ure 2). Specifically, wet pen conditionswere associated with higher pen preva-lence than pens in normal condition(Wilcoxon rank sums, P=0.01).The prevalence of fecal sheddingwithin feedlot cattle herds and pens hasbeen reported to be low. However, thereliability of E. coli O157:H7 preva-lence estimates in cattle may vary by thediagnostic method employed, the num-ber of cattle sampled and the type ofsamples collected. The overall 23 per-cent of fecal shedding observed in thisstudy is consistent with other reportssuggesting that at times the organismmay be widespread in beef cattle popu-lations. For example, in a recent Cana-dian study, the organism was recoveredfrom 19.7 percent of fecal samples col-lected at slaughter from yearling cattleand cull cows during the summer months(Van Donkersgoed et al. 1999 CanadianVet J. pp 332-338).The pen prevalence of fecal sheddingdid not differ between the five feedyards.This finding suggests that E. coliO157:H7 may be ubiquitous to feedlotcattle populations. In a multistate cross-sectional study, researchers cultured thefeces of 120 cattle each (4 pens x 30 fecalpats) in 100 feedyards (Hancock et al.1997 J Food Prot. pp 462-465). Thissampling strategy may prevent detectionof low prevalence pens. Despite a lowoverall prevalence of shedding (1.6%),E. coli O157:H7 was found in 61% of thefeedyards surveyed. Other surveys, us-ing serology (Laegreid et al. 1998 ConfRes Workers Anim Dis P26) and bacte-rial culture of feces (Sargeant et al. 1998Conf Res Workers Anim Dis Abstract41), suggest that exposure to E. coliO157:H7 is widespread and most beefcattle have been exposed to the organ-ism before weaning. Because of com-mingling, widespread exposure of cattleto E. coli O157:H7 after arrival in largecattle feedlots is plausible, at least dur-ing certain seasons. Cattle recentlyarriving in the feedyard have been dem-onstrated to be at greater risk for shed-ding E. coli O157 than cattle on feedlonger (Dargatz et al. 1997 J Food Protpp 466-470).All pens we observed had some cattleshedding the organism in the feces. Inspite of the apparent ubiquity of theorganism, the pen-prevalence of cattleshedding E. coli O157:H7 varied greatlywithin each feedyard. Pens with highand low prevalence of fecal sheddingwere observed in each feedyard. Fac-tors that explain the variability in pen-prevalence of E. coli O157:H7 fecalshedding may be risk factors that couldbe managed as control points in aHACCP-based feedlot productionfood safety program.The environmental condition of thepen was the only pen characteristic thatwas associated with pen prevalence.Figure 2. Percentage of cattle shedding detectable Escherichia coli O157:H7 in pens subjectivelyclassified by pen environment as: 1-dry and dusty, 2-normal condition, 3-wet andmuddy. Compared to pens with normal environmental conditions, pens classified as wetand muddy had significantly greater pen prevalence of E. coli O157:H7.Pen Condition1009080706050403020100Percent of pen shedding O157:H7    1 2     3Pen Condition Score(Continued on next page)2001 Nebraska Beef Report — Page 84Pens with the greatest percentage ofcattle shedding E. coli O157:H7 weremore likely to be wet and muddy at thetime of sample collection. Pens withdusty conditions were intermediate inthe percentage of cattle shedding theorganism. The association between theenvironmental condition of a pen and thepercentage of cattle shedding E. coliO157:H7 seems plausible. Compared tothe normal pen conditions, muddy ordusty conditions would be expected tofacilitate fecal-oral transmission ofenteric agents because of greater oppor-tunity for the agent to move with water ordust particles.It is unlikely that selection bias wasintroduced by voluntary recruitment ofthe feedyards or selection of cattle pensby convenience. There was no priorknowledge of the E. coli O157:H7 statusof any of the feedyards. Pens wereselected for inclusion in the study withconsideration for the feedyards’re-implanting schedule and the work-load of the laboratories. When there wasan option, pens with fewer cattle werepreferentially chosen for study to mini-mize costs. Pens were selected withoutknowledge of the results from previouspens in the feedyards.The results of this study suggest thatE. coli O157:H7 should be consideredan ubiquitous organism in pens offeedlot cattle and that factors in the penenvironment may help to explain theprevalence of cattle shedding the organ-ism. The limited time-period of the study(summer months) and the cross-sectionalnature of the study did not permitobserving the effect of time dependentvariables on the outcome of pen preva-lence. It would be interesting to observechanges in pen prevalence over time aspen conditions change.1David Smith, assistant professor, Veterinaryand Biomedical Sciences, Lincoln; MarkBlackford, graduate student, Animal Science,Lincoln; Spring Younts, graduate student,Veterinary and Biomedical Sciences, Lincoln;Todd Milton, assistant professor, Animal Science,Lincoln; Rodney Moxley, professor, Jeff Gray,assistant professor, Veterinary and BiomedicalSciences, Lincoln; Laura Hungerford, associateprofessor, Great Plains Veterinary EducationalCenter, Clay Center; Terry Klopfenstein, professor,Animal Science, Lincoln.A Diagnostic Strategy to ClassifyPens of Feedlot Cattle by thePrevalence of Escherichia coliO157:H7 Fecal Sheddingfood-safety would be maximized ifHACCP principles were applied at alllevels of food production and process-ing. Unfortunately, there is insufficientknowledge of the epidemiology and ecol-ogy of E. coli O157:H7 to design andimplement HACCP-based food safetyprograms in cattle feedyards.Research or development of on-farmHACCP programs to control E. coliO157:H7 in feedlot production systemshave been hampered by difficulty indetermining the infection status of cattleat any point in time. The difficulty indiagnosis results because infection withE. coli O157:H7 in cattle occurs withoutclinical signs, except in calves, and be-cause there is a lack of field-validatedmethods to monitor livestock for foodsafety pathogens.Determining if individual live cattleare shedding E. coli O157:H7 is expen-sive and impractical. For example, cul-ture of the feces from most, if not all,animals in a feedlot pen requires con-siderable labor and supplies. Handlingfinished cattle prior to shipping is notdesirable because of the loss in value tocattle due to shrink, dark cutters andbruising. It may be possible to controlE. coli O157:H7 in feedlots withoutknowing the infection status of indi-vidual cattle because control points orinterventions for reducing human food-borne pathogens in feedlot cattle wouldmost likely be directed towards pens ofcattle. Therefore, the E. coli O157:H7status of pens of feedlot cattle is animportant outcome for feedlot produc-tion food safety research and HACCPmonitoring.Research and development ofHACCP-based feedlot food safety pro-grams could advance if pens of cattle,rather than individuals, could be accu-rately and economically classified byDavid SmithSpring YountsMark BlackfordRodney MoxleyJeff GrayLaura HungerfordTodd MiltonTerry Klopfenstein1This diagnostic strategy can beused in food-safety research or as amonitoring tool in animal produc-tion food-safety programs to clas-sify feedlot pens by the percentageof cattle shedding Escherichia coliO157:H7.SummaryThis study evaluated two pen testingstrategies to predict the percentageof cattle in a pen shedding detectableE. coli O157:H7. Culture of a compos-ite fecal sample most accuratelydetected pens with 37% or more cattleshedding E. coli O157:H7 in feces. Anew pen test device most accuratelydetected pens with 16% or more indi-viduals shedding. The likelihood of de-tecting E. coli O157:H7 with eithermethod increased as pen prevalenceincreased. If both pen-level test meth-ods were used together, pens could beclassified as high, medium or low preva-lence with less labor and expense thantesting individual cattle.IntroductionThe principles of hazard-analysis-critical-control-points (HACCP) weredeveloped to minimize the likelihoodthat food will be contaminated with po-tentially dangerous pathogens. Ideally

The Relationship of the Characteristics of Feedlot Pens to the Percentage of Cattle Shedding \u3ci\u3eEscherichia coli\u3c/i\u3e O157:H7 Within the Pen

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1320&amp;context=animalscinbcr

The Relationship of the Characteristics of Feedlot Pens to the Percentage of Cattle Shedding \u3ci\u3eEscherichia coli\u3c/i\u3e O157:H7 Within the Pen

Abstract

Similar works

Full text

Available Versions

DigitalCommons@University of Nebraska