What We know (and don’t know) About Pneumonia in Beef Calves Prior to Weaning - David R. Smith, DVM, PhD, DACVPM, Mississippi State University College of Veterinary Medicine, from the 2014 NIAA Annual Conference titled 'The Precautionary Principle: How Agriculture Will Thrive', March 31 - April 2, 2014, Omaha, NE, USA. More presentations at http://www.trufflemedia.com/agmedia/conference/2014_niaa_how_animal_agriculture_will_thrive

1. What we know (and don’t know) about
pneumonia in beef calves prior to weaning
David R. Smith, DVM, PhD
Mississippi State University
College of Veterinary Medicine

2. Is pneumonia an emerging disease
of pre-weaned beef calves?
Where do emerging diseases come from?
System Dynamics
• Emergence of a novel agent
• Acquire new virulence factors
• Introduction into a new geo-political region
• Emergence of a known, previously controlled, agent
• Emergence of a susceptible host (genetic, nutritional …)
• Emergence of a production system that favors a
particular pathogen
Increased Awareness
• Mitigation of a disease of greater impact
• Social interest –everyone’s suddenly talking about it…

3. Pre-Weaning
Pneumonia in
Beef Calves

4. Pre-Weaning Pneumonia
in Beef Calves
Host-pathogen interactions
Population dynamics

5. Bovine Respiratory Disease
• Recent NAHMS surveys confirm that BRD is the leading
cause of mortality in U.S. feedlot cattle, weaned dairy
heifers, and nursing beef calves 3 weeks of age or older
–all classes of cattle
• BRD deaths alone cost producers over $643 million
annually (2010 estimate, USDA NASS)
• Thus BRD has a significant impact on the profitability of
cattle operations and on the health and welfare of cattle

6. Cost of pre-weaning pneumonia
29,000,000 US beef cow inventory
24,650,000 85% calves born alive
147,900 0.6% excess death loss due to BRD
400 weaned calf lbs
1.90$ price per pound
112,404,000$ 760.00$ losses due to excess BRD mortality
1,479,000 6% treated calves
36,975,000 25 lbs weaning wt lost from treated calves
70,252,500$ losses due to lost weaning wt from BRD
22,185,000$ 15.00$ cost to treat a calf for BRD
204,841,500$ Total cost of BRD prior to weaning.

7. JAVMA, Vol 243, No. 4, August 15, 2013 538-547
Objective—To identify herd-level risk factors for bovine respiratory
disease (BRD) in nursing beef calves.
Design—Population-based cross-sectional survey.
Sample—2,600 US cow-calf producers in 3 Eastern and 3 Plains
states.
Results –Bovine respiratory disease had been detected in at least 1
calf in 21% of operations

8. JAVMA, Vol 243, No. 4, August 15, 2013 538-547
“Detection of BRD in calves was significantly
associated with large herd size, detection of BRD in
cows, and diarrhea in calves. Calving season length
was associated with BRD in calves in Plains states
but not Eastern states.
Cumulative incidence of BRD treatment was
negatively associated with large herd size and
examination of cows to detect pregnancy and
positively associated with calving during the winter,
introduction of calves from an outside source,
offering supplemental feed to calves, and use of an
estrous cycle synchronization program for cows.”

9. AABP Research Summaries, Milwaukee, WI. Sept 19, 2013
A survey of veterinarians in 6 U.S. states regarding their
experience with nursing beef calf respiratory disease
Amelia R. Woolums, Roy D. Berghaus, David R. Smith, Brad J. White,
Terry J. Engelken, Max B. Irsik, Darin K. Matlik, A. Lee Jones, Isaiah
J. Smith
Results
Respondents reported that 18% of their cow-calf clients had nursing
calf BRD in the previous year, with 5% of their cow-calf clients
having 5% or greater incidence, and 14% of their clients having at
least one calf die of BRD.

10. AABP Research Summaries, Milwaukee, WI. Sept 19, 2013
A survey of veterinarians in 6 U.S. states regarding their
experience with nursing beef calf respiratory disease
Amelia R. Woolums, Roy D. Berghaus, David R. Smith, Brad J. White,
Terry J. Engelken, Max B. Irsik, Darin K. Matlik, A. Lee Jones, Isaiah
J. Smith
Results
From a list of possible risk factors for nursing calf BRD, at least 50% of
respondents selected “weather”, “inadequate colostrum consumption”,
“introducing new cattle”, “failure to give nursing calves BRD vaccines”,
“failure to give cows BRD vaccines”, “calf diarrhea in the herd”,
“vitamin/mineral deficiency for cows/calves”, “protein/energy deficiency
for cows/calves”, “BVDV PI cattle in the herd”, and “calving cows and/or
heifers in confinement” as contributing to nursing calf BRD.
Component causes!

11. Component causes
• Disease is not observed until the sum of
component causes complete a sufficient
cause
• The agent may be necessary for disease
• The agent alone may not be sufficient to cause
disease
Mannh.
hemol.
BVDV
Cold
D
E
BVDV
Dust
X
Z
Mannh.
hemol.
Mannh.
hemol.
PI3
Dust
N
O
Sufficient cause 1 Sufficient cause 2 Sufficient cause 3…

12. • Infection is common but disease is rare
• Until something makes the system “unstable”
–then an apparent disease outbreak
• Complete a sufficient cause
• Introduce a new risk factor
• e.g. Bovine respiratory disease complex
• e.g. Salmonella
• Loss of herd immunity
• Age (e.g. neonatal calf diarrhea)
• Immunosuppression
• Remove antigenic challenge (e.g. stop vaccinating)
 Disease control programs may create naïve subpopulations –
susceptible to outbreaks! eg. BVDV
Component Causes
Explain Endemic Stability

13. Time dependent factors of the
production system affect
pathogen exposure and the
immune response
• Passive
immunity
• Age
• Pathogen
survival
• Pathogen
exposure
• Stressors
• Nutrition
• Parasitism
• Pregnancy
Weaning
Surgery
Mud
Heat
Cold
Nutrition,
Genetics…
Commingling

14. Immunity
Exposure
Time
Exposure and
immunity as a
function of
time
BRD in Pre-weaned
Calves: When and
Why?

15. Agents

16. Immunity Active immune
response
Passive Acquired
Antibodies from
colostrum
Age

17. Immunity
Passive
Antibodies from colostrum
Age
T1/2 of antibodies
from colostrum is 16
days
Roth. 2009. Current Vet Therapy
Food Anim Pract
0%
20%
40%
60%
80%
100%
0 30 60 90 120 150 180

18. Immunity
Antibodies from colostrum
Age
T1/2 of antibodies
from colostrum is 16
days
Roth. 2009. Current Vet Therapy
Food Anim Pract
2048
512
128
Initial antibody titer

19. Immunity Active immune
response
Age
The immune system is functional, but
unprimed, at birth
Prior to 5-8 months of age the immune
response is weaker, slower, and easier
to overcome.
Cortese. 2009. Vet Clin NA, 25(1)221-227

20. Kirkpatrick JAVMA, Vol 233, No. 1, July 1, 2008

21. Kirkpatrick et al. JAVMA, Vol 233, No. 1, July 1, 2008
Early: 67d, 190d
Late: 167d, 190d

22. Kirkpatrick et al. JAVMA, Vol 233, No. 1, July 1, 2008 Early: 67d, 190d
Late: 167d, 190d

23. Age and
immunity to
BRD
Incidence of BRD by
age
• 14 years
• Pre-weaning data
• 14,792 steer calves
• Surviving to
feedlot finish
Smith DR. 2013.
Unpublished

24. Pre-weaning BRD
Herd 1
• Age distribution of
87 pneumonia
cases from among
296 pre-weaned
calves from a
Nebraska ranch
• 29% cumulative
incidence

25. Pre-weaning BRD
Herd 2
• Age distribution of
49 pneumonia
cases from among
255 pre-weaned
calves from a
Nebraska ranch
• 19% cumulative
incidence

26. Pre-weaning BRD
Herd 3
• Age distribution of 96
summer pneumonia
cases from 2,065 calves
born over a 4 year
period.
• 5% cumulative incidence

27. Pre-weaning BRD
Herd 4
• Age distribution of 138
summer pneumonia
cases from 630 calves
born in 2012
• 22% cumulative
incidence

28. 110,412 calves
20 years

29. “…there seem to be two periods of increasing BRD
transmission rate (0 to 20, and 70 to 100 d of age)….
Epidemiological studies of these phases may lead to
management alternatives to decrease BRD incidence.”
Snowder et al. 2005. J Anim Sci
110,412 calves
20 years

30. “The greater incidence between 75 and 170 d of age
may be partially attributed to increased commingling of
animals during the breeding season when cows were
frequently gathered for AI.”
Snowder et al. 2005. J Anim Sci
110,412 calves
20 years

31. Herd immunity
• Transmission is hindered because a
majority of animals are immune –inefficient
transmission means the pathogen may “die
out” (R0 <1) before everyone is exposed
• Results in protection of susceptible animals
within the group
• Better to be the susceptible calf within a pen of
well-immunized cattle, than the only one
vaccinated
• For this reason successful vaccine programs are
“group-based”

32. BRSV SN titers
179 calves serially
sampled
As calves in the
population age the
distribution of titers
shifts to the left
Leaving a smaller
proportion of calves
protected and a
larger proportion of
calves susceptible
Data provide by A Woolums

33. BRSV SN titers
179 calves serially
sampled
As calves in the
population age the
distribution of titers
shifts to the left
Leaving a smaller
proportion of calves
protected and a
larger proportion of
calves susceptible
Data provide by A Woolums

34. BRSV SN titers
179 calves serially
sampled
As calves in the
population age the
distribution of titers
shifts to the left
Leaving a smaller
proportion of calves
protected and a
larger proportion of
calves susceptible
Data provide by A Woolums

35. Epidemic Curve
Herd 1
• Epidemic
curve of BRD
in Herd 1.
• Lines
represent the
proportion of
calves at least
100 or 120
days of age
each week.

36. Epidemic Curve
Herd 2
• Epidemic
curve of BRD
in Herd 2.
• Lines
represent the
proportion of
calves at least
100 or 120
days of age
each week.

37. Epidemic Curve
Herd 4
• Epidemic curve of BRD in Herd 4.
• Lines represent the proportion of
calves at least 100 or 120 days of
age each week.

38. Age and
immunity to
BRD
Incidence of BRD by
age
• 14 years
• Pre-weaning data
• 14,792 steer calves
• Surviving to
feedlot finish
Smith DR. 2013.
Unpublished

39. Age and BRD
by year
Mean days of age at
BRD treatment = 89.4
Median = 91.4
• 14 years
• Pre-weaning data
• 14,792 steer calves
• Surviving to feedlot
finish
• Error bars = 1 stdev
Smith DR. 2013.
Unpublished

40. BRD by year
• 14 years
• Pre-weaning data
• 14,792 steer calves
• Surviving to feedlot
finish
• Significant
differences by year
in BRD cumulative
incidence
Smith DR. 2013.
Unpublished

42. Ranch vs
Feedlot BRD
Incidence of BRD
on the ranch
appeared
unrelated to
incidence of
feedlot BRD
Smith DR. 2013.
Unpublished
Line of equivalence
Ranch incidence greater
Feedlot incidence greater

43. Ranch vs
Feedlot BRD
Some years calves
with BRD on the
ranch were at
greater risk for
BRD in the
feedlot, some
years it was the
opposite.
Smith DR. 2013.
Unpublished

44. Calf gender is associated with BRD risk
5,078 calf records from 4
ranches and 20
management groups.
Adjusting for age of the
dam, heifer calves were less
likely (OR = 0.83) and bull
calves more likely (OR =
1.46) than steers to develop
BRD prior to weaning
(p=0.01)

45. Age of the dam is associated with BRD risk
5,078 calf records from 4
ranches and 20
management groups.
Adjusting for gender,
compared to calves born to
cows 4 years or older, calves
with two year old dams and
3 year old dams had 1.67
and 1.11 times greater odds
for BRD (p=0.0004)

46. Conclusions from ranch BRD
outbreak investigations
Calf level characteristics:
• Age of the dam affects BRD risk
• Gender of the calf may affect BRD risk
Herd level characteristics:
• Two patterns of occurrence of pneumonia
• sporadically in young calves
• large sudden outbreaks in older calves

47. Conclusions from ranch BRD
outbreak investigations
The explanation of these two patterns
may be:
• failure of passive transfer resulting in more
sporadic cases in very young calves
• Loss of herd immunity resulting in outbreaks of
pneumonia in older calves.

48. Conclusions from ranch BRD
outbreak investigations
• Herd immunity (or lack of it) may play an important role in the
occurrence of pneumonia in ranch calves.
• Increased incidence of BRD in calves ~90-150 days of age
• Sudden outbreaks of BRD when a large portion of the herd is in this age
range
• Lose endemic stability
• Susceptible = potentially infective resulting in overwhelming exposure
• Other time related environmental/management factors may
affect pathogen exposure and host susceptibility

49. Acknowledgements
• Amelia Woolums, UGA
• Dale Grotelueschen, UNL GPVEC
• Suzanne Genova, MSU
• Russ Daly, SDSU
• Gerald Stokka, NDSU
• Al Doster, Dustin Loy, Bruce Brodersen UNL VDC
• Many ranchers and veterinarians throughout the US
A contribution of the Beef Cattle Population Health Program at Mississippi State University.
Supported by the Mikell and Mary Cheek Hall Davis Endowment for Beef Cattle Health and
Reproduction.
Supported in part by a grant from Zoetis