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M. J. Schneider, R. G. Tait, Jr., W. D. Busby and J. M. Reecy
performance and carcass traits using treatment records and lung lesion scores
An evaluation of bovine respiratory disease complex in feedlot cattle: Impact on
doi: 10.2527/jas.2008-1283 originally published online Jan 30, 2009;
2009.87:1821-1827. J Anim Sci
http://jas.fass.org/cgi/content/full/87/5/1821
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ABSTRACT: The objective of this study was to in-
vestigate the effects of bovine respiratory disease (BRD)
complex on economically important production traits
with the use of health records in combination with lung
lesion scores obtained at slaughter. Records from 5,976
animals were used in this study from cattle that were
managed in Midwestern feedlots. Average daily gain for
3 different feeding periods (acclimation, on-test, and
overall test) along with final BW were evaluated as per-
formance measures. Hot carcass weight, LM area, sub-
cutaneous fat cover, and marbling score were collected
at slaughter. All calves were monitored by experienced
feedlot personnel and treated according to the specific
health protocol of each feedlot. Incidence of BRD was
observed at a rate of 8.17%, and lung lesions at slaugh-
ter were present in 61.9% of cattle from a subpopula-
tion (n = 1,665). From this group of cattle, the overall
incidence of BRD, which was defined as cattle that had
lung lesions, that were treated for BRD in the feedlot,
or both, was 64.4%. Incidence of BRD in the feedlot de-
creased ADG during both the acclimation period (0.37
± 0.03 kg) and the overall test period (0.07 ± 0.01 kg).
Incidence of BRD also had significant effects on HCW
and marbling score with reduction of 8.16 ± 1.38 kg
and 0.13 ± 0.04, respectively, in treated cattle. The ad-
verse effects on production traits tended to increase as
the number of treatments increased. Potential decrease
in performance and carcass merit observed in this study
were associated with a decline of $23.23, $30.15, and
$54.01 in carcass value when comparing cattle never
treated with cattle treated once, twice, or 3 or more
times, respectively. The presence of lung lesions did not
have a significant effect on any of the traits; however,
there was an association between the presence of active
bronchial lymph nodes and less productivity of feedlot
cattle.
Key words: bovine respiratory disease, cattle, treatment record
©2009 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2009. 87:1821–1827
doi:10.2527/jas.2008-1283
INTRODUCTION
Bovine respiratory disease (BRD) complex is the
biggest health obstacle the cattle industry faces due to
the economic ramifications. The economic cost associ-
ated with BRD has been reported to cost the industry
$750 million annually (Griffin, 1997). The average cost
of 1 treatment was estimated at $15.57 (Faber et al.,
1999). This cost is amplified to $92.26 (McNeill et al.,
1996) when indirect costs are also considered such as
the reduction of ADG and less carcass value due to a
less desirable quality grade.
Bovine respiratory disease complex is commonly ob-
served throughout the feedlot phase due to the stress
factors that cattle face such as transportation, commin-
gling from different sources, and feedlot processing. The
incidence rate of clinical BRD was reported as 14.4% by
USDA-APHIS (2001), from a study of feedlots from 12
states in 1999. Lung lesions at slaughter are extremely
common with an observed prevalence ranging between
29.7 and 77% (Wittum et al., 1996; Bryant et al., 1999;
Thompson et al., 2006) in feedlot cattle.
The first objective of this study was to examine the
effects of BRD incidence and the frequency of treat-
ments on economically important performance and
An evaluation of bovine respiratory disease complex in feedlot cattle:
Impact on performance and carcass traits using treatment
records and lung lesion scores1,2
M. J. Schneider,* R. G. Tait Jr.,* W. D. Busby,† and J. M. Reecy*3
*Department of Animal Science, Iowa State University, Ames 50011;
and †Cooperative Extension Service, Iowa State University, Lewis 51544
1
This journal paper was funded by contributions from the Nation-
al Beef Cattle Evaluation Consortium and from the USDA Coopera-
tive State Research, Education, and Extension Service. This journal
paper of the Iowa Agriculture and Home Economics Experiment
Station, Ames (project No. NRSP-8) was supported by Hatch Act
and State of Iowa funds.
2
The authors thank the Tri County Steer Carcass Futurity (TC-
SCF) organization for allowing the use of their records to complete
this research. We greatly appreciate everyone for being extremely
helpful throughout this process. In addition, thank you to Dee Grif-
fin from the USDA Meat Animal Research Center (Clay Center, NE)
and Mike Wells from Pfizer (Kalamazoo, MI) for their willingness to
train on lung scoring.
3
Corresponding author: jreecy@iastate.edu
Received July 9, 2008.
Accepted January 19, 2009.
1821
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carcass traits. The second objective was to examine
the effect of lung lesion scores, an indicator of overall
BRD, obtained at slaughter on these same traits in
feedlot cattle. The third objective was to evaluate the
economic impact of BRD.
MATERIALS AND METHODS
All procedures were approved by the Iowa State Uni-
versity Animal Care and Use Committee.
The data analyzed within this study came from the
Tri County Steer Carcass Futurity (TCSCF) test lo-
cated in Southwest Iowa. Data included performance,
carcass, health records, and a portion of the cattle had
lung lesion scores collected at slaughter. This study uti-
lized 5,976 cattle, which entered the feedlot between
2003 and 2006. These cattle were consigned to TCSCF
and were fed in 10 different feedlots. The fed cattle
utilized in this study were from herds across the Mid-
west and Southeast United States. In total, 105 cattle
(1.43%) died in the feedlot, in which 49% of deaths
were attributed to BRD, 40% of deaths were due to
reasons unrelated to BRD, and 11% of deaths were re-
lated to unknown causes.
Calves were processed on arrival to the Iowa feedlots
where they were tagged, weighed, implanted, and vac-
cinated. Bulls and horned cattle were omitted from the
test. Cattle were fed a receiving diet for a period of 4
to 6 wk at which time on-test BW were collected and
cattle were started on an 80% concentrate diet. Pens of
cattle were marketed at least 2 different time periods
5 wk apart based on last known BW of cattle and the
visual appearance of market readiness by the feedlot
management. Carcass data were collected on slaugh-
tered cattle at the packing plant by trained TCSCF
personnel.
Health Management
Cattle were observed regularly by feedlot personnel
for signs of sickness. Cattle were classified as having
been treated for BRD when observed with BRD symp-
toms. Symptoms of BRD included labored breathing,
coughing, decreased appetite, depression, droopy ears,
eye discharge, fever, nasal discharge, and death. The
specific health management for each feedlot was deter-
mined by the particular feedlot manager.
Lung Lesion Scoring
Cattle were slaughtered at a commercial packing
plant (Tyson Foods, Denison, IA), where lungs were
scored at chain speed as they passed by on a conveyor
belt. Scoring was recorded and then matched to live
identification at a later time. The lung lesion scoring
system implemented in this study (D. Griffin, USDA
Meat Animal Research Center, Clay Center, NE, per-
sonal communication) consisted of slight modifications
to procedures used by Bryant et al. (1999). Scoring was
as follows: 0 = normal, no lesions observed; 1 = affect-
ed area involved less than 1 anterior ventral (AV ) lobe
and less than 5% lung volume; 2 = adhesions, affected
area, or both in more than 1 AV lobe with greater than
5% but less than or equal to 10% of lung volume; 3 =
adhesions affecting more than 1 AV lobe, greater than
10% to less than or equal to 15% lung volume affected,
a small portion of lung missing, or a combination of
these; 4 = more than 15% missing lung volume; and
5 = active bronchial lymph nodes. All scores were as-
signed by visual observations only; no physical han-
dling of lungs was performed.
Overall BRD
Overall BRD incidence was defined as an animal that
expressed symptoms of BRD and was treated, had lung
lesions present at slaughter, or a combination of both.
Cattle that were pulled and treated expressed visual
symptoms such as labored breathing, coughing, de-
creased appetite, depression, droopy ears, eye discharge,
fever, or nasal discharge. This definition was used to
evaluate animals that were thought to be truly affected
by respiratory problems during the feedlot phase and
to estimate the effects of overall BRD on performance
and carcass traits.
Statistical Analysis
The GLM procedure (SAS Inst. Inc., Cary, NC) was
used to estimate the effects of BRD on performance
and carcass traits. The number of records evaluated
for each trait is listed in Tables 1 and 2. Performance
traits analyzed included acclimation ADG (early feed-
ing period; initial 4 to 6 wk), on-test ADG (late feeding
period; end of acclimation period until slaughter), over-
all ADG (total feedlot period), and final BW. Carcass
traits consisted of HCW, LM area, subcutaneous fat
cover (fat), and marbling score (MarbS; 2.00 = Prac-
tically Devoid00; 3.00 = Traces00; 4.00 = Slight00; 5.00
= Small00; 6.00 = Modest00; 7.00 = Moderate00; 8.00 =
Slightly Abundant00; 9.00 = Moderately Abundant00;
10.00 = Abundant00).
Bovine respiratory disease incidence is defined as a
binary classification of 0 for untreated and 1 for infect-
ed based on at least 1 feedlot treatment. The number
of BRD (NoTrt) treatments was defined as the follow-
ing: 0 if cattle were never treated for BRD, 1 if cattle
were treated once for BRD, 2 if cattle were treated
twice for BRD, and 3+ if cattle were treated thrice or
greater (thought to be suffering from chronic illness
with BRD). Lesion presence was measured as with or
without (binary) the presence of lung lesions at slaugh-
ter. Lung score was measured as an ordinal variable
associated with different levels of severity as described
previously. Overall, BRD was defined as the combina-
tion of BRD incidence, lung lesions, or both, observed
at slaughter time.
Schneider et al.
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Analysis was completed for BRD incidence, number
of BRD treatments, lesion presence, lung score, and
overall BRD using the following model to estimate the
effect of BRD on performance traits:
yijklm = TRTi + CGj + Sexk + DelWtl
+ SDm(CGj) + εijklm,
where yijklm = the trait measured on calf l, in treatment
i, in contemporary group j, of sex k, and in slaughter
date m; TRTi = fixed effect of BRD incidence i, NoTrt
i, lesion presence i, lung score i, or overall BRD i; CGj
= fixed effect of contemporary group j (based on group
of cattle that entered feedlot together and fed together
through the feedlot phase); Sexk = fixed effect of sex k
(steer or heifer); DelWtl = linear effect of the delivery
weight of calf l; SDm(CGj) = fixed effect of final slaugh-
ter date m nested within contemporary group j; εijklm =
residual with
e seijklm ~N0, 2
()
.
For the analysis of car-
cass measures, similar fixed effects were fitted; however,
the linear effect of DelWt was replaced with the linear
effect of age at slaughter (AgeH).
Economic Analysis
An analysis was also conducted to evaluate the mon-
etary values associated with the different BRD treat-
ment classifications. All economic results are reported
in the form of US dollars. The first analysis was made
on the actual income that cattle received. This income
was calculated by multiplying the HCW by the base
carcass price with the addition of carcass premiums
or discounts paid per animal. The difference in value
directly due to ADG and carcass quality grade was also
investigated. The live price used in this study was de-
termined by averaging the price of live cattle during
the time period that cattle were slaughtered (USDA,
Livestock Marketing Information Center, 2007b). The
average price, $87.10/45.5 kg, was then multiplied
by the overall ADG of each calf throughout the feed-
lot period, and then multiplied by days on feed. The
Table 1. Significance value for fixed sources of variation for growth traits in feedlot cattle by type of bovine respi-
ratory disease (BRD) measurement used
Item n R2
Model effect1
TRT CG SD(CG) Sex DelWt
BRD incidence2
Acclimation ADG 5,795 0.55 <0.01 <0.01 <0.01 <0.01 <0.01
On-test ADG 5,976 0.51 0.24 <0.01 <0.01 <0.01 <0.01
Overall ADG 5,976 0.50 <0.01 <0.01 <0.01 <0.01 <0.01
Final BW 5,976 0.63 <0.01 <0.01 <0.01 <0.01 <0.01
No. of BRD treatments3
Acclimation ADG 5,795 0.55 <0.01 <0.01 <0.01 <0.01 <0.01
On-test ADG 5,976 0.51 0.10 <0.01 <0.01 <0.01 <0.01
Overall ADG 5,976 0.50 <0.01 <0.01 <0.01 <0.01 <0.01
Final BW 5,976 0.63 <0.01 <0.01 <0.01 <0.01 <0.01
Lesion presence4
Acclimation ADG 1,665 0.38 0.46 <0.01 0.01 <0.01 0.13
On-test ADG 1,665 0.53 0.37 <0.01 <0.01 <0.01 <0.01
Overall ADG 1,665 0.53 0.64 <0.01 <0.01 <0.01 <0.01
Final BW 1,665 0.61 0.81 <0.01 <0.01 <0.01 <0.01
Lesion score5
Acclimation ADG 1,665 0.38 0.18 <0.001 <0.01 <0.01 0.12
On-test ADG 1,665 0.53 0.03 <0.001 <0.01 <0.01 <0.01
Overall ADG 1,665 0.54 0.01 <0.001 <0.01 <0.01 <0.01
Final BW 1,665 0.61 <0.01 <0.001 <0.01 <0.01 <0.01
Overall BRD6
Acclimation ADG 1,665 0.38 <0.01 <0.01 <0.01 <0.01 0.11
On-test ADG 1,665 0.53 0.49 <0.01 <0.01 <0.01 <0.01
Overall ADG 1,665 0.53 0.52 <0.01 <0.01 <0.01 <0.01
Final BW 1,665 0.61 0.39 <0.01 <0.01 <0.01 <0.01
1TRT = BRD incidence, No. of BRD treatments, lesion presence, lesion score, and overall BRD; CG = contemporary group; SD(CG) = final
slaughter date within contemporary group; sex = steer or heifer; age = day age at slaughter.
2BRD incidence = untreated (0) vs. treated (1).
3NoTrt is equal to 0 = nontreated cattle; 1 = cattle treated once; 2 = cattle treated twice; 3+ = cattle treated 3 or more times.
4Lesion presence = cattle with no lung lesions vs. cattle with lung lesions.
5Lesion score is equal to 0 = normal, no lesions observed; 1 = affected area involved less than 1 anterior ventral (AV) lobe and less than 5%
lung volume; 2 = adhesions, affected area more than 1 AV lobe with greater than 5% of lung volume, or both; 3 = adhesions affecting more than
1 AV lobe, greater than 10% lung volume affected, a small portion of lung missing, or a combination of these; 4 = more than 15% missing lung
volume; and 5 = active bronchial lymph nodes.
6Overall BRD is equal to cattle treated, cattle with lung lesions, or both. Acclimation ADG = early feeding period; on-test ADG = late feeding
period; overall ADG = total feedlot period, and final BW = last BW before slaughter.
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differences in premiums or discounts paid for USDA
Prime, Choice, Select, and Standard quality grades
were determined by averaging these values over this
same time period (USDA, Livestock Marketing Infor-
mation Center, 2007a). The value given to each USDA
quality grade was as follows: $8.35/45.5 kg for Prime,
$0.00/45.5 kg for Choice, $−10.33/45.5 kg for Select,
and $−18.63/45.5 kg for Standard. The differences in
the quality grade were then multiplied by the HCW of
each animal.
RESULTS AND DISCUSSION
In total 5,976 animals were utilized to analyze the
effects of BRD incidence on performance and carcass
traits, whereas the number of cattle with lung lesion
data observed was 1,665 (Table 1). The majority of
the cattle fed were steers, 4,791 (80%), whereas 1,185
were heifers (20%). The average BW upon entering the
feedlot was 288 ± 44 kg, average age upon delivery was
287 ± 60 d, and mean on-test BW was 343 ± 49 kg.
Mean acclimation ADG was 1.54 ± 0.69 kg, mean on-
test, ADG was 1.44 ± 0.29 kg, mean overall ADG was
1.46 ± 0.25 kg, and mean final BW was 539 ± 50 kg.
The average HCW was 331 ± 32 kg, the mean LM area
was 80.90 ± 7.87 cm2, the mean subcutaneous fat was
11.18 ± 3.30 mm, and the mean marbling score was
5.30 ± 0.82.
Incidence rate of BRD in this study of feedlot cattle
totaled 8.17%, which is similar to the 8.7% reported in
feedlots of similar size (USDA-APHIS, 2001). A total
of 488 cattle were treated for BRD, of which 53% were
treated once, 34% were treated twice, and 13% were
treated thrice or more. The average day of first treat-
ment was 40 d after entering the feedlot and 75% of
treated cattle had been treated by d 55. This underlines
the observation that first few weeks upon entering the
feedlot is the most critical time period to observe cattle
for BRD.
Table 2. Significance value for fixed sources of variation for carcass traits in feedlot cattle by type of bovine re-
spiratory disease (BRD) measurement used
Item n R2
Model effect1
TRT CG SD(CG) Sex AgeH
BRD incidence2
HCW 5,976 0.36 <0.01 <0.01 <0.01 <0.01 <0.01
LM area 5,976 0.24 0.08 <0.01 <0.01 <0.01 <0.01
Fat 5,976 0.23 <0.01 <0.01 <0.01 <0.01 0.11
MarbS 5,976 0.30 <0.01 <0.01 <0.01 <0.01 <0.01
No. of BRD treatments3
HCW 5,976 0.36 <0.01 <0.01 <0.01 <0.01 <0.01
LM area 5,976 0.24 0.22 <0.01 <0.01 <0.01 <0.01
Fat 5,976 0.23 <0.01 <0.01 <0.01 <0.01 0.11
MarbS 5,976 0.31 <0.01 <0.01 <0.01 <0.01 <0.01
Lesion presence4
HCW 1,665 0.36 0.26 <0.01 <0.01 <0.01 <0.01
LM area 1,665 0.19 0.20 <0.01 0.19 <0.01 <0.01
Fat 1,665 0.20 0.39 <0.01 <0.01 <0.01 0.27
MarbS 1,665 0.28 0.94 <0.01 0.03 <0.01 <0.01
Lesion score5
HCW 1,665 0.36 <0.01 <0.01 <0.01 <0.01 <0.01
LM area 1,665 0.19 0.16 <0.01 0.16 <0.01 <0.01
Fat 1,665 0.20 0.14 <0.01 <0.01 <0.01 0.29
MarbS 1,665 0.28 0.64 <0.01 0.03 <0.01 <0.01
Overall BRD6
HCW 1,665 0.36 0.08 <0.01 <0.01 <0.01 <0.01
LM area 1,665 0.19 0.09 <0.01 0.18 <0.01 <0.01
Fat71,665 0.20 0.25 <0.01 <0.01 <0.01 0.25
MarbS81,665 0.28 0.93 <0.01 0.03 <0.01 <0.01
1TRT = BRD incidence, No. of BRD treatments, lesion presence, lesion score, and overall BRD; CG = contemporary group; SD(CG) = final
slaughter date within contemporary group; sex = steer or heifer; age = day age at slaughter.
2BRD incidence = untreated (0) vs. treated (1).
3No. of BRD treatments is equal to 0 = nontreated; 1 = treated once; 2 = treated twice; and 3 = treated 3 or more times.
4Lesion presence = no lung lesions vs. lung lesions present.
5Lesion score is equal to 0 = normal (no lesions observed) 1 = affected area involved less than 1 anterior ventral (AV) lobe and less than 5%
lung volume; 2 = adhesions, affected area, or both in more than 1 AV lobe with greater than 5% of lung volume; 3 = adhesions affecting more
than 1 AV lobe, greater than 10% lung volume affected, a small portion of lung missing, or a combination of these; 4 = more than 15% missing
lung volume; and 5 = active bronchial lymph nodes.
6Overall BRD is equal to cattle treated, cattle with lung lesions, or both.
7Fat = subcutaneous fat cover.
8MarbS = marbling score.
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For lung lesion scoring, the lungs of 1,665 cattle were
observed at slaughter, with 61.9% of the lungs having
lesions present. The percentage of cattle with lung le-
sions was similar to the results reported by Wittum et
al. (1996) and Bryant et al. (1999), but greater than
reported by Thompson et al. (2006). The distribution
of lung lesion scores were as follows: 0 = 38.1%; 1 =
26.9%; 2 = 16.2%; 3 = 11.7%; 4 = 3.1%; and 5 = 4.0%.
Lung lesions were found in 60.6% of cattle that were
never treated for BRD, possibly indicating that feedlot
observation simply missed a large number of cattle that
suffered from BRD, many of these cattle suffered from
subclinical disease, that lesions observed were from in-
stances of BRD exposure before arrival to the feedlot,
or a combination of these. Lesions were also observed in
most (74%) cattle that had been treated at least once.
It is also important to note that treatment for BRD
within these feedlots may not be completely effective
in limiting the impact of disease or that some cases
were severe enough to cause long-term effects within
the respiratory system. These results indicate that lung
lesions are present not only in cattle with known infec-
tion of BRD, but also in cattle thought to be healthy
and that a more accurate evaluation of BRD incident
is determined with the use of both phenotypes. Also,
a portion of treated animals (26%) did not have lung
lesion present at slaughter, indicating that treatment
for those cattle may have prevented any damage that
infection may cause to the lungs.
Overall, BRD in this study was defined as any animal
treated for BRD, any animal having lung lesions pres-
ent at slaughter, or both. The estimated overall BRD
incidence totaled 64.4% of cattle and may be a more
accurate assessment of the true incidence of BRD in
this population. This value is greater than the number
of cattle treated for BRD (8.17%), but only slightly
larger than cattle with lung lesions present at slaughter
(61.9%).
Performance Traits
Sources of variation for growth traits in feedlot cattle
by BRD incidence, number of treatments, lung lesion
presence, lung scores, and overall BRD are presented in
Table 1. Significant differences between treated and un-
treated cattle as well as the number of treatments were
observed for acclimation ADG (P < 0.01), overall ADG
(P < 0.01), and final BW (P < 0.01); however, there
was no significant impact on on-test ADG. Treatment
for BRD was associated with a reduction of 0.37 ± 0.03
kg in acclimation ADG (Table 3) and a reduction of
0.07 ± 0.01 kg in overall ADG, indicating that cattle
suffer the largest losses in performance during the early
feeding period after entering the feedlot and some de-
gree of subsequent compensatory BW gain is observed
in treated cattle. The overall ADG reduction observed
in this study is similar to the results reported by Bate-
man et al. (1990) and Gardner et al. (1999). The es-
timates among cattle in different treatment categories
illustrate that as the number of treatments increased
performance decreased.
The analysis of lesion presence revealed no signifi-
cant effects (P > 0.05) on performance traits (Table 1).
However, severity of lung scores had significant effects
on on-test ADG (P < 0.05), overall ADG (P < 0.01),
and final BW (P < 0.01). In regard to on-test ADG,
Table 3. Least squares means for performance and carcass traits where the effect of bovine respiratory disease
(BRD) was found to be significant
Item
Least squares mean
Untreated SE Treated SE Diff1SE
BRD incidence2
Acclimation ADG,3** kg/d 1.51 0.01 1.14 0.03 0.37 0.03
Overall ADG,4** kg/d 1.44 0.01 1.37 0.01 0.07 0.01
Final BW,5** kg 531 0.90 520 1.75 11 1.65
HCW,† kg 323 0.75 315 1.46 8.16 1.38
LM area,† cm279.48 0.19 78.90 0.39 0.58 0.32
Fat,6** mm 11.68 0.08 10.92 0.18 0.76 0.25
MarbS,7 ** 5.38 0.02 5.25 0.04 0.13 0.04
Overall BRD8
Acclimation ADG,3** kg/d 1.48 0.03 1.41 0.02 0.07 0.03
HCW,† kg 330 1.68 327 1.39 3 1.73
LM area,† cm281.42 0.39 80.77 0.32 0.65 0.39
1Diff = untreated minus treated.
2BRD incidence = untreated (0) vs. treated (1).
3Acclimation ADG = early feeding period.
4Overall ADG = total feedlot period.
5Final BW = last BW before slaughter.
6Fat = subcutaneous fat cover.
7MarbS = marbling score. 2.00 = Practically Devoid00; 3.00 = Traces00; 4.00 = Slight00; 5.00 = Small00; 6.00 = Modest00; 7.00 = Moderate00;
8.00 = Slightly Abundant00; 9.00 = Moderately Abundant00; 10.00 = Abundant00.
8Overall BRD is equal to cattle treated, cattle with lung lesions, or both.
**P-value = ≤ 0.01; †P-value ≤ 0.10.
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overall ADG, and final BW, there were no differences
observed between lesion scores of 0, 1, 2, 3, or 4 (P >
0.05); however, when compared with lungs classified
as a 5, which represents presence of active bronchial
lymph nodes, significant differences (P < 0.05) were
detected.
Carcass Traits
The significance of each fixed effect included in the
model for carcass traits are listed in Table 2. Incidence
of BRD and number of treatments described a signifi-
cant amount of variation in HCW (P < 0.01), subcu-
taneous fat cover (P < 0.01), and marbling score (P <
0.01). Untreated cattle had more desirable estimates
for all carcass traits when compared with treated cattle
(Table 3). Specifically, a reduction of 8.16 ± 1.38 kg in
HCW, 0.58 ± 0.32 cm2 for LM area, 0.76 ± 0.25 mm
in fat cover, and 0.13 ± 0.04 in marbling score was
observed in cattle treated for BRD. Similar to perfor-
mance traits, HCW and marbling score decreased as
the number of BRD treatments increased. In addition,
untreated cattle were fatter at slaughter (P < 0.01) and
tended to be heavier muscled (P < 0.08).
Greater than 71% of cattle that were never treated
graded Choice or better, whereas cattle treated once,
twice, and thrice or more graded Choice or greater 57,
55, and 52%, respectively, of the time. Frequency dif-
ferences were significant when comparing any of the
treated categories with untreated cattle (P < 0.05).
There were, however, no significant differences (P >
0.05) between the treated categories. These findings
have important economic consequences due to the fact
that there are considerable discounts paid for Select and
Standard carcasses. When untreated cattle are com-
pared with the chronically ill cattle that were treated
at least 3 times, the frequency of cattle that fell within
the Standard grade was 5 times greater. These results
are similar to that of McNeill et al. (1996).
The presence of lung lesions at slaughter did not have
a significant (P > 0.05) impact on the carcass traits
evaluated; however, lung scores had a significant effect
on HCW (P < 0.01). The difference for HCW was seen
when comparing lungs with or without active bronchial
lymph nodes. Contrary to Gardner et al. (1999), lung
score had no significant effect on marbling score. Dif-
ferences between these results could be due to the dif-
ferences in the lung scoring systems implemented or the
genetic background of the 2 populations.
Overall BRD
When the incidence of BRD and the presence of lung
lesions were combined the effects that overall BRD has
on performance and carcass traits was able to be ex-
amined. Results for overall BRD are presented in Table
3. Overall BRD significantly effected acclimation ADG
(P < 0.01) with a difference of 0.07 ± 0.03 kg/d be-
tween treated and untreated cattle. It is possible that
the difference in acclimation ADG was primarily due to
the difference observed in treated cattle. Interestingly,
overall BRD incidence had no significant effect on on-
test or overall ADG. This indicates that when the com-
bination of treatment and lung lesion are considered,
cattle were able to compensate for losses in BW gain
during the later feeding period, or some cattle exhibit-
ing lung lesions may have been affected by BRD before
their arrival to the feedlot. Also of interest is that cattle
falling within the overall BRD category of untreated
tended to have heavier HCW (P < 0.08) and be heavier
muscled (P < 0.09).
Economics of BRD Treatment
The differences in carcass value when considering
the carcass premiums and the actual price received
are presented in Figure 1. When untreated cattle were
compared with BRD treatment classifications of 1, 2,
and 3+, there was a difference of $23.23, $30.15, and
$54.01, respectively, from untreated cattle. Cattle pro-
ducers are interested in increasing profitability, and
cattle not suffering from BRD were more valuable in
this study (P < 0.01).
Due to the fact that these value estimates only reflect
differences within a specific marketing scheme, an anal-
ysis of economic value due to performance and quality
grade separately was conducted. Differences in value
due to differences in ADG were $15.76, $22.09, and
$46.70 when comparing cattle that were never treated
for BRD with cattle in the 1, 2, and 3+ classifications,
respectively. The decreased economic values attributed
to differences in quality grade when compared with cat-
tle that were never treated were $7.48, $9.58, and $7.70
for 1, 2, and 3+ classifications, respectively. These val-
ues underestimate total economic losses associated with
BRD in this study as they do not account for the extra
cost of treatment associated with medicine cost, labor,
veterinarian fees, and death loss.
Figure 1. Least squares means for actual cattle gross income.
Treatment of cattle for bovine respiratory disease (BRD) is classified
as 0 = no treatment; 1 = treated once; 2 = treated twice; and 3+ =
treated 3 or more times. a–cLeast squares means with different letters
are statistically different (P < 0.10).
Schneider et al.
1826
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Conclusions
The results of this study indicate that BRD morbid-
ity and the extent of treatment have major consequenc-
es on performance and carcass traits. Substantial per
animal losses in income were observed for cattle treated
for BRD, which may be attributed to the effects of
BRD due to the combination of decreased performance
and carcass quality.
The presence of lung lesions did not greatly influence
any of the traits considered within this study; how-
ever, the greatest loss of production was in cattle that
had active bronchial lymph nodes at slaughter. This
outcome was somewhat different than other reports on
the effects of lung lesions on performance and carcass
traits. Thus, there is a need to determine the extent to
which lung lesions observed at slaughter could be from
infection before entering the feedlot, and second, re-
searchers must be cognizant of limitations to physically
manipulate lungs and the consequence that this may
have on possible misclassification of lungs.
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