1
2
3
4
5
6
7
8
9
Does Feeding Distillers Grains in Rations
Increase E. coli O157:H7?
Terry Klopfenstein, Dave Smith, Galen Erickson and Rod Moxley
University of Nebraska-Lincoln
Introduction
In 1997 Hudson Foods in Columbus, NE, recalled 25 million pounds of ground beef
10
because it was positive for E. coli O157:H7. A few months later Beef America, a regional packer
11
in Norfolk, NE, had a ground beef recall. Both recalls bankrupted the companies. That got our
12
attention in Nebraska especially, but across the national beef industry as well. Meat and Poultry
13
Magazine calculated that the ten-year cost of E. coli O157:H7 from ’93 to ’03 was about $2.7
14
billion. The public health cost was estimated at $989 million per year. We have learned a
15
considerable amount about E. coli O157:H7 in the past 15 years.
16
Background on E. coli O157:H7
17
Prior to 1998, it was believed that the prevalence of E. coli O157:H7 in feedlot cattle was
18
low ─ perhaps 2 to 3% of all cattle being positive. New analytical techniques essentially
19
increased this prevalence by a factor of about 10. This procedure uses an IMS technique which
20
effectively ”finds” the E. coli O157:H7 in cattle feces. Feces have been the most common
21
material measured to determine if cattle are positive for E. coli O157:H7. Cattle feces contain
22
hundreds of types of bacteria measured in millions or more of bacteria per gram. Some of these
23
are coliform bacteria, including generic E. coli, which are not typically pathogens. So finding the
24
E. coli O157:H7 is like “finding the needle in the haystack”.
25
Using the IMS and other more sensitive analytical techniques, we followed 100 steers
26
through a summer feeding period ─ sampling them weekly. Prevalence was low (Figure 1) until
27
mid July and then increased from less than 10% to 80% over a two-week period. Prevalence then
1
28
declined to about 30%. We did not identify reasons for the dramatic change (Khaitsa et al.,
29
2003). We sampled cattle in 74 pens in five commercial feedlots (Figure 2). Prevalence averaged
30
30% in the summer and each of the 44 pens sampled in the summer had at least one positive
31
animal (Smith et al., 2001). The range was from 1 to 80% positive animals ─ the variation
32
largely unexplained (Smith et al., 2001). Prevalence was only 6.1% in winter months and 14 of
33
30 pens had no positive animals. Still the range in prevalence was 0 to 56%. We concluded that
34
probably all feedlots have E. coli O157:H7 positive cattle and prevalence is higher in the summer
35
than winter and prevalence is highly variable and the variation is largely unexplained.
36
Elder et al. (2000) sampled cattle entering the packing plant and then the carcasses after
37
slaughter. They showed a positive relationship between E. coli O157:H7 positive cattle entering
38
the plant and the number of positive carcasses. It is believed the carcass gets contaminated from
39
the hide as it is being removed. Because the contamination is on the surface of the carcass, the
40
trim has the E. coli O157:H7 and is mixed into the ground beef as it is processed. The packing
41
industry has done an excellent job in intervention (Koohmaraie et al., 2005). This includes
42
carcass washes, steam pasteurization, organic acid rinses and “test and hold”. Test and hold is a
43
procedure where trimmings are sampled and tested for E coli O157:H7 and “held” before
44
processing. Only trimmings testing negative are ground. The small number of positives are heat
45
processed to destroy the organism. With these excellent interventions, the percentage of positive
46
samples declined from about 0.8% in 2000 to about 0.2% the past four years.
47
Unfortunately, 2007 was not a good year for ground beef safety and recalls. There were
48
eight recalls in 2006 and all of them were initiated because of company sampling. In 2007, there
49
were 20 recalls and nine of theses recalls resulted from illness investigation. This was(is) a
50
problem for the cattle industry and health officials looked for reasons why E. coli O157:H7
2
51
seemed to be a greater problem in 2007 compared to the previous four years. Because the ethanol
52
industry grew in 2007 and had attracted attention because of the effect on corn prices, some
53
theorized that feeding ethanol byproducts was the cause of the E. coli O157:H7 recalls. Late in
54
2007, research from Kansas State showing a connection between distillers grains (DG) feeding
55
and E. coli O157:H7 shedding was reported. The media, looking for a good story, made the
56
Kansas State research findings look like a food safety crisis. Let’s look at the data from Kansas
57
State and Nebraska and see if it confirms the media hype.
58
59
Distillers Grains and E. coli O157:H7 Shedding
The Kansas State researchers have reported four studies. Jacob et al. (2008a) reported a
60
study using 370 feedlot cattle sampled at 122 and 136 days on feed. Prevalence overall was fairly
61
low (under 10%). On day 122 cattle were statistically more likely to shed E. coli O157:H7 when
62
fed 25% DG in the diet. On day 136 there was no effect of feeding DG. Jacob et al. (2008b)
63
sampled cattle for 12 weeks during the feeding period. Samples were fecal samples collected
64
from the pen floor. Feeding DG significantly increased E. coli O157:H7 shedding although there
65
was no difference on five of the 12 sampling periods.
66
The third Kansas State study was a challenge experiment where calves were inoculated
67
with nalidixic acid resistant E. coli O157:H7. This allowed the researchers to estimate the
68
number of E. coli O157:H7 shed. Fecal samples were collected for 42 days. E. coli O157:H7
69
shedding was not different for calves fed DG during the first five weeks but was statistically
70
greater during the last week of sampling. Based on these three studies, the Kansas State
71
researchers concluded that DG feeding increased E. coli O157:H7 shedding. In each of the three
72
experiments there were sampling times when DG statistically increased shedding, however, as
3
73
with most results in E. coli O157:H7 research, the results were somewhat inconsistent making
74
interpretation of the results somewhat difficult.
75
Recently, the Kansas State researchers have reported to the Kansas Livestock Assoc.
76
results of an experiment supported by the Kansas Beef Council and NCBA (Nagaraja et al.,
77
2008). Seven hundred cattle were fed for 150 days ─ half were fed DG. Pen floor samples were
78
collected weekly or every two weeks and a total of 3,560 samples were collected and analyzed.
79
This is a large scale study with good statistical power. Overall prevalence was fairly low (5.1%).
80
“Although prevalence of E. coli O157:H7 in pen floor fecal samples was numerically higher on
81
some sampling weeks in cattle fed DDGS, there was no significant effect of DDGS (P = 0.2)”.
82
All of the Kansas State studies were conducted with steam-flaked corn (SFC) diets with
83
or without 25% (DM basis) DG. This may be important as we compare the Nebraska research to
84
the Kansas State research. Corrigan (2007) has shown that DG do not respond the same in SFC
85
diets compared to dry-rolled corn (DRC) or high moisture corn diets (HMC) (Figure 3). If cattle
86
gains and efficiencies respond differently to DG levels in SFC and DRC or HMC diets, then it is
87
possible that any effect on E. coli O157:H7 might respond differently as well. The Nebraska E.
88
coli O157:H7 research is with DRC or HMC only.
89
It is logical that the diet fed to cattle could influence the growth of E. coli O157:H7 in the
90
hindgut. Research has shown that the primary reservoir of E. coli O157:H7 is the hindgut and
91
that the E. coli O157:H7 attach to the intestinal wall of the hindgut. Interestingly, the E. coli
92
O157:H7 have no effect on cattle performance. There are two opposing theories on how the diet
93
affects E. coli O157:H7 in the hindgut. The first theory is that starch escaping digestion in the
94
rumen and small intestine is fermented in the hindgut producing volatile fatty acids and lowering
95
pH. This is theorized to inhibit growth of the E. coli O157:H7. Fox et al. (2007) showed support
4
96
for this theory. Steam flaking reduced starch in the hindgut and increased E. coli O157:H7
97
shedding. However, Depenbusch et al. (2008) said “E. coli O157:H7 was not related to fecal pH
98
or starch”. We reanalyzed the data of Peterson et al. (2007a) where diets with decreasing
99
amounts of corn were fed ─ decreasing the amount of starch in the diet. Amount of starch in the
100
101
diet was not related to E. coli O157:H7 shedding (P = .22).
The opposing theory is that starch in the hindgut is the substrate for E. coli O157:H7 so
102
by reducing the amount of starch getting to the hindgut, E. coli O157:H7 would be reduced.
103
Peterson et al. (2007a) and Folmer et al. (2003) showed this did not work. While it is logical that
104
diet affects E. coli O157:H7 growth in the hindgut, clearly neither of the two opposing “starch
105
theories” have been “proven” so we look for other possible theories.
106
The Nebraska research on the effect of DG on E. coli O157:H7 shedding was reported by
107
Peterson et al. (2007b). The research was primarily focused on vaccination as an E. coli
108
O157:H7 intervention. Because the study was superimposed on a nutrition study, we reanalyzed
109
the data (Figure 4). Wet DG were fed as 0, 10, 20, 30, 40 and 50% of diet dry matter replacing
110
DRC and HMC. In this experiment samples of the hindgut mucosa were analyzed as well as
111
fecal samples. Results were similar but more consistent for the mucosal samples (Figure 4).
112
There was a significant effect of level of DG on E. coli O157:H7 shedding, however, it was not a
113
linear relationship. None of the levels of DG feeding were statistically different from the control
114
(ODG). The 10, 20, and 30% DG levels numerically decreased the shedding of E. coli O157:H7.
115
Interesting, this is within the range of feeding (25%) the Kansas State researchers used. Our
116
research is with DRC and HMC while their research is with SFC which may well make a
117
difference.
5
118
At the 40 and 50% DG feeding level, E. coli O157:H7 shedding numerically increased
119
compared to the control. Note that the statistical difference is between the 10, 20, and 30% DG
120
levels and the 40 and 50% levels. So does DG decrease or increase E. coli O157:H7 shedding?
121
The media (Des Moines Register, January 27, 2008) chose the negative approach ─ “studies at
122
the University of Nebraska suggest feeding DG increases levels of a DEADLY form of E. coli
123
bacteria”.
124
Peterson et al. (2007b) were studying vaccination. The pattern of E. coli O157:H7 in
125
hindgut mucosa for unvaccinated cattle is similar to that discussed previously (Figure 5).
126
However, there was only one positive steer among the vaccinated cattle and that was at the 50%
127
DG feeding level. So which is more important, finger pointing at feed ingredients such as DG or
128
looking for interventions? Over four studies involving 1,784 cattle, vaccination has reduced E.
129
coli O157:H7 shedding by 65%. This is equivalent to the effect of winter versus summer on
130
shedding. Feeding a direct-fed microbial (Peterson et al. (2007a) reduced shedding over two
131
years by 35%. These two interventions plus others being researched have considerable merit.
132
Conclusions
133
1. It is reasonable to think that what we feed cattle might affect the bacterial population of
134
the hindgut. This has already been demonstrated in different studies.
135
2. Research at Kansas State and University of Nebraska-Lincoln both suggest that under
136
some feeding levels and some other, as yet unknown, conditions, DG may increase E.
137
coli O157:H7 shedding.
138
3. Results of E. coli O157:H7 research in general and specifically with DG feeding are
139
inconsistent. To date, there has been no demonstrably consistent effect of DG feeding on
140
E. coli O157:H7 shedding.
6
141
4. Response in E. coli shedding to DG feeding may be affected by DG level and other
142
dietary ingredients such as the corn type. The issue is highly complex and more research
143
is needed to address the many factors, including those feed components given
144
concurrently with DG, that could be involved.
145
5. Interventions and research on interventions is much more important than “finger
146
pointing” at different feedstuffs, especially when data are inconsistent and more research
147
is needed.
148
6. At this point, there is no scientific evidence that feeding DG, at least at levels being used
149
commercially, is the cause of a food safety crisis! Additionally, there is no scientific
150
evidence to suggest that the feeding of DGs is the cause of the 2007 recalls.
151
152
References
Corrigan, Mark C., Galen E. Erickson, Terry J. Klopfenstein, Kyle J. Vander Pol, Matthew A.
153
Greenquist, and Matthew K. Luebbe. 2007. Effect of corn processing and wet distillers grains
154
inclusion level in finishing diets. Nebraska Beef Cattle Report. MP-90:33-35.
155
Depenbusch, B. E., T. G. Nagaraja, J. M. Sargeant. J. S. Drouillard, E. R. Loe, and M. E.
156
Corrigan. 2008. Influence of processed grains on fecal pH, starch concentration and shedding
157
of E. coli O157:H7 in feedlot cattle. J. Anim. Sci. 86:632-639.
158
Elder, R. O., Keen, J. E., Siragusa, G. R., Barkocy-Gallagher, G. A. Koohmaraie, M., and
159
Laegreid, W. W. (2000). Correlation of enterohemorrhagic Escherichia coli O157 prevalence
160
in feces, hides, and carcasses of beef cattle during processing. Proceedings of the National
161
Academy of Sciences of the United States of America, 97-2999-3003.
7
162
Folmer, Jeffrey, Casey Macken, Rod Moxley, David Smith, Mindy Brashears, Suzanne Hinkley,
163
Galen Erickson, and Terry Klopfenstein. 2003. Intervention strategies for reduction of E. coli
164
O157:H7 in feedlot steers. Nebraska Beef Report. MP 80-A:22-23.
165
Fox, J. T., B. E. Depenbusch, J. S. Drouillard, and T. G. Nagaraja. 2007. Dry-rolled or steam-
166
flaked grain-based diets and fecal shedding of E. coli O157:H7 in feedlot cattle. J. Anim. Sci.
167
85:1207-1212.
168
Jacob, M. E., J. T. Fox, S. K. Narayanan, J. S. Drouillard, D. G. Renter, and T. G. Nagaraja.
169
2008a. Effects of feeding wet corn distiller’s grains with solubles with or without monensin
170
and tylosin on the prevalence and antimicrobial susceptibilities of fecal food-borne
171
pathogenic and commensal bacteria in feedlot cattle. J. Anim. Sci. 2008. In press Eprint
172
available. doi:10.2527.
173
Jacob, M. E., J. T. Fox, J. S. Drouillard, D. G. Renter, and T. G. Nagaraja. 2008b. Effects of
174
dried distillers’ grains on fecal prevalence and growth of Escherichia coli O157 in batch
175
culture fermentations from cattle. Appl. Environ. Microbial. 74:38-43.
176
Jacob, M. E., G. L. Parsons, M. K. Shelor, J. T. Fox, J. S. Drouillard, D. U. Thomson, D. G.
177
Renter, and T. G. Nagaraja. 2008c. Feeding supplemental dried distiller’s grains increases
178
fecal shedding Escherichia coli O157 in experimentally inoculated calves. Zoonoses Publ.
179
Hlth (Accepted for Publication).
180
Khaitsa, M. L., D. R. Smith, J. A. Stoner, A. M. Parkhurst, S. Hinkley, T. J. Klopfenstein, and R.
181
A. Moxley. 2003. Incidence, duration and prevalence of Escherichia coli O157:H7 fecal
182
shedding by feedlot cattle during the finishing period. J. of Food Protection, Vol. 66, No. 11,
183
1972-1977.
8
184
Koohmaraie, M., T. M. Arthur, J. M. Bosilevac, M. Guerini, S. D. Shackelford, and T. L.
185
Wheeler. 2005. Post-harvest interventions to reduce/eliminate pathogens in beef. Meat
186
Science 71:79-91.
187
Nagaraja, T. G., J. Drouillard, D. Renter, S. Narayanan. 2008. Distillers grains and food-born
188
pathogens in cattle: Interaction and intervention. KLA News and market Report Vol. 33, No.
189
35.
190
Peterson, R. E., T. J. Klopfenstein, G. E. Erickson, J. Folmer, S. Hinkley, R. A. Moxley, and D.
191
R. Smith. 2007a. Effect of Lactobacillus Strain NP51 on Escherichia coli O157:H7 fecal
192
shedding and finishing performance in beef feedlot cattle. J. Food Prot. 70, No. 2:287-291.
193
Peterson, R. E., T. J. Klopfenstein, R. A. Moxley, G. E. Erickson. S. Hinkley, G. Bretschneider,
194
E. M. Berberov, D. Rogan, and D. R. Smith. 2007b. Effect of a vaccine product containing
195
type III secreted proteins on the probability of E. coli O157:H7 fecal shedding and mucosal
196
colonization in feedlot cattle. J. Food Protection. Vol. 70, No. 11:2568-2577.
197
Smith, D. R., M. P. Blackford, S. M. Younts, R. A. Moxley, J. T. Gray, L. L. Hungerford, C. T.
198
Milton, and T. J. Klopfenstein. 2001. Ecological relationships between the prevalence of
199
cattle shedding Escherichia coli O157:H7 and characteristics of the cattle or conditions of the
200
feedlot pen. J. Food Prot. 64 (12) 1899-1903.
9
Longitudinal study
Research Feedyard
Khaitsa et al. 2003. J Food Prot 66 (11)
1972-1977.
100%
90%
Conditions of natural
O157:H7 exposure
70%
Prevalence
Feces from100 steers
(10 pens of 10) cultured
each week
80%
60%
50%
40%
30%
E. coli O157:H7 recovered
every week and at least
once from every animal
20%
10%
0%
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19
Week
Conclusions
E. coli O157:H7 is ubiquitous to cattle populations
Variable in prevalence by TIME and PLACE
Figure 1.
This project was supported by the National
Research Initiative of the USDA Cooperative
State Research, Education and Extension
Service, grant number #0002501.
Prevalence of cattle shedding E. coli O157:H7
Summer 1999 / 2002
44 pens of cattle
Prevalence
Summer E. coli O157:H7
• 4,952 cattle, 44 pens
– 1,501 culture positive (30%)
– EVERY pen (100%)
– Variable prevalence (1(1-80%)
Winter E. coli O157:H7
• 2,941 cattle, 30 pens
– 179 culture positive (6.1%)
– 16/30 pens (53%)
– Variable prevalence (0(0-56%)
• Significant difference by season
Smith DR, et al. 2001.
J Food Prot 64 (12) 1899-1903
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1
4
7
10 13 16 19 22 25 28 31 34 37 40 43
pens ranked by prevalence
Prevalence of cattle shedding E. coli O157:H7
Winter 2000 / 2001 / 2002
30 pens of cattle
Prevalence
Seasonal prevalence
of fecal shedding in
commercial feedyards
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29
pens ranked by prevalence
Figure 2.
10
WDGS & Grain Processing
6.5
Feed/Gain
6.0
5.5
5.0
y = -0.0186x + 6.1219
R2 = 0.9617
4.5
DRC
HMC
SFC
y = -0.0085x + 5.4226
4.0
R2 = 0.767
3.5
y = -0.0003x + 5.4653
R2 = 0.0078
3.0
0
10
20
30
40
Level of diet DM (WDG)
Corrigan et al., 2007 Nebraska Beef Rep.
Figure 3.
Effect of level of distiller’s grains on
E. coli O157:H7 colonization by cattle
b
0.25
0.2
Probability
Wet distiller’s
grains plus
solubles
replaced
corn in each
treatment
diet
b
0.15
0.1
0.05
ab
a
a
a
0
00DG 10DG 20DG 30DG 40DG 50DG
Diet
Figure 4.
11
Colonization of
non-vaccinated cattle
Colonization of
vaccinated cattle
Figure 5.
12