Fa Med - Bovine Respiratory Disease Complex

Front 1

The study of ruminant respiratory disease is inseparably linked with:

Back 1

-production medicine

Front 2

What is production medicine?

Back 2

Physiology of the normal and diseased animal and disease agent are affected by:
-prevention & therapy
-production system
-food safety & market system

Front 3

Typical timeline of the beef industry

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Birth ---> weaning (205 days/6.8 months) ---> direct placement in feedlot ----> slaughter (14-15 months)

Birth ---> weaning (205 days) ---> background stocker (6)---> feedlot (4) ----> slaughter (17-18 months)

Birth ---> weaning (205 days) ---> background stocker (2) ---> feedlot (7) ----> slaughter (15-16 months)

Front 4

BRDC
-when is the highest incidence in the beef industry

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-weaning (205 days/6.8 months)

Front 5

Beef inductry
-what happens to cows and calves on pasture

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-enough heifer calves kept to replace 20% of the cows or replacement heifers are purchased
-Rest of the calves move into the production cycle after weaning
-Cows sold around 10 yrs old after producing at least 8 calves

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Beef industry
-what happens to calves after weaning

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-enter next phase of production under the same or new ownership
-if sold, either done through direct sale or a salebarn

Front 7

Beef industry
-what happens to almost all calves

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-almost all calves not retained in the herd as heifers or bulls will go through a final feedlot production phase

Front 8

Environment
-how it contributes to disease

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-if the environment is made unfavorable we can contribute to disease incidence

Front 9

BRDC
-ruminant physiological predisposition to disease

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-ruminant lung is more conducive to respiratory disease than other species

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Nutrition
-effect on disease

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-negative energy balance will have a harder time resisting a disease challenge

Front 11

BRDC
-morbidity

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-Beef calves still nursing the cow: sporadic occurance with occasional outbreaks (30-40%)

-Housed Calves: common to treat >10% with high morbidity (>50%)

-Adult dairy cows: 10-30% morbidity reported in some herds., Usually low prevalence.

-Feedlot cattle: 75% morbidity and 50% mortality

Front 12

BRDC
-high risk feedlot cattle vs. low risk feedlot cattle

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High risk
- >10% morbidity
- 5-10% case fatality

Low risk
- <10% morbidity
- 1-3% fatality

Front 13

BRDC
-management factors

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-comingling
-closer quarters in feedlots than on grassland (can still have on grass though)
-shipping
-colostrum status can affect BRDC morbidity in the feedlot

Front 14

BRDC
-why is comingling such a big factor in feedlots

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-want size continuity in groups of cattle, so cattle from multiple sources are put together
-larger number of sources ---> mix of new pathogens for the cattle
-adding new cattle to the pen constantly brings in new pathogens and shakes up the social order

Front 15

BRDC
-reasons shipping affects prevalence

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-stress
-diesel exhaust
-dehydration

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Why do we commingle multiple small groups or single animals in a pen?

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-cowherd size influence (smaller herds contribute more to sources of cattle in a feedlot pen)
-need for size consistency in feedlot pen cattle
-sorting will increase in the feedlot

Front 17

How to get ahead of the effects of commingling

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Address the immune status of calves at:
-birth
-preweaning
-immediately post-weaning

*failure of passive transfer at birth is linked to increased morbidity

Front 18

BRDC
-anatomical factors of cattle that cause prevalence

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-terminal bronchial units have no cross communication for clearance of infectious debris

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BRDC
-lung lobe most affected

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-right cranioventral

Front 20

BRDC
-% of lung consolidation

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-50-60%

Front 21

Respiration
-4 division

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-pulmonary ventilation (bulk flow)
-diffusion
-transport in the body
-regulation of ventilation

Front 22

BRDC
-most important division of respiration that is affected

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-diffusion

Front 23

BRDC
-respiratory signs related to

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-efforts of the animal to get air (ventilation)

Front 24

Respiration
-how to tell what kind of a job the lungs are doing

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relationship between:
-diffusion
-ventilation
-blood flowing through the lung

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Bovine
-normal ventilatory efficiency

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1/3 (33%) of what the cow breaths is usable to exchange for O2

2/3 of each breath do not reach the alveoli

---> higher PaCO2

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BRDC
-effect on calf respiration

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-less ventilation
-poor diffusion

working harder to get less air

*will die without intervention

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BRDC
-viral components

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-IBR (infectious bovine rhinotracheitis)
-BVD (Bovine viral diarrhea)
-BRSV (Bovine respiratory syncytial virus
-PI3 (Parainfluenza type 3)

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BRDC
-bacterial components

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Gram (-)
-Mannheimia haemolytica
-Pasteurella multocida
-Histophilus somni
-Mycoplasma bovis
-Bibersteinia trehalosi

Gram (+) = secondary invaders
-Staph
-Strep
-Trueperella multocida

Front 29

Mannheimia haemolytica
-found where`

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-nasal/tonsil cultures of cattle (commensal organism)

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Mannheimia haemolytica
-forms

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-Type A2: prevalent in non-diseased cattle

Type A1: rapidly multiples and overwhelms tracheal and pulmonary defenses (ciliary defense mechanism); switch from A2 induced by stress

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Mannheima haemolytica
-how it affects animal

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-leukotoxins: impede the cellular immune response

-endotoxins: systemic adverse effects leading to depression and anorexia

-necrotic debris: close terminal bronchi which snowballs to consolidate a large part of the lung if not stopped

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BRDC
-drug spectrums for different bacteria importance

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-can talk about generalized spectrums, but it really depends on the individual isolate

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Look at Mannheimia drug spectrums in lecture

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Look at Mannheimia drug spectrums in lecture

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Where is antibiotic resistance a large problem in Mannheimia haemolytica?

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-where resistance to all drugs is in the same isolates

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Trueperella multocida
-isolated from

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-chronic cases

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Trueperella multocida
-effect

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-secondary pathogen: adult and feedlot cattle

-primary pathogen: young calves, housed calves

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BRDC
-how to make a large difference in prevalence in housed calves

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-proper ventilation
-reasonable biosecurity

*better than vaccines

Front 38

Histophilus somni
-pathology

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-Respiratory disease
-TEME (thromboembolic meningioencephalitis)
-arthritis
-cardiac muscle necrosis

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Mycoplasma bovis
-reason for prevalence

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Secondary pathogen
-our ability to help cattle survive primary pathogens

Front 40

Mycoplasma bovis
-lesions

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-respiratory lesions
-multiple sites of tenosynovitis

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Mycoplasma bovis
-labeled drugs

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-Tulathromycin
-Gamithromycin
-Florfenicol
-Enrofloxacin

Front 42

Mycoplasma bovis
-susceptibility testing

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-hampered by growth requirements and lack of approved breakpoints

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Mannheimia haemolytica and Pasteurella multocida
-bacterial component vaccine types
-efficacy

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-subunit
-modified live
-combination vaccine


-efficacy: variable; best chance when given before stress

Front 44

Histophilus somni vaccine
-efficacy

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-variable effect
-better at preventing TEME and joint problems than respiratory disease (but not proven)

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Mycoplasma bovis vaccine
-efficacy

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-no proof in any efficacy
-possible increase in lung lesions

Front 46

Different types of production systems

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-pasture
-building
-confinement lots

*all have different potential for disease

Front 47

Apley's pathognomonic lesion from H. somni

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-Ventricle papillary muscle lesion