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North Dakota State University, Dr. Charlie Stoltenow,
Extension Veterinarian, Dr. Greg Lardy, Extension Beef
Specialist
Bovine Resiratory Disease (BRD)
Bovine respiratory disease complex (BRD) is the
leading cause of morbidity and mortality in feedlots.
Additionally, many animals develop respiratory tract
disease but may not be identified as sick. These
animals have decreased average daily gains and poorer
carcass characteristics than healthy animals.
This complex is manifested as one entity,
bronchopneumonia. Yet, it can be caused by a variety
of factors that interact to cause severe respiratory
distress and possibly death. BRD in beef calves is
called shipping fever, because the greatest incidence
of bronchopneumonia occurs after shipment to stocker
operations or feedlots. The main cause of BRD illness
in calves is the tremendous exposure to infectious
agents along with stress associated with weaning,
commingling, and transportation.
Clinical Signs
The clinical symptoms of BRD usually develop five to
14 days following management or environmental
stresses. Signs can be variable due to the many
causative agents possibly involved in the disease
complex. Signs include:
- anorexia
(not eating)
- rapid
and labored breathing
- depression
and weakness
- droopy
ears
- coughing
- nasal
and ocular discharge (runny nose and eyes)
- fever
(up to and over 104 F; normal is 101.5 F)
- stiff
and/or staggering walking movement
- hanging
back from the rest of the herd
- sudden
death
Treatment
Any treatment program objectives should include:
- Reduction
of death loss
- Reduction
in the rate of chronic cases
- Improvement
of performance in calves that have been sick
- Improvement
of animal welfare
- Cost
effectiveness
Sick animals should be isolated from other animals in
the herd. It keeps them from passing the infection to
others, competition with other animals for feed,
water, and space is reduced, and it facilitates
monitoring and retreatment, if needed.
Mass Medication vs. Individual Animal Treatment
Should you medicate the individual animal or the
whole herd? Obviously, each sick animal should be
treated, or they will have a very high risk of dying.
If the illness is complicated by bacteria, appropriate
antibiotic selection can be made through consultation
with your veterinarian and using culture and
sensitivity tests performed on tissues collected at
necropsy.
Mass medication, antibiotics given on arrival to all
cattle, is a management strategy that has gained
acceptance and has been demonstrated to be effective
and economical under certain conditions. The exact
mechanism by which mass medication therapies work to
improve health is not known. One explanation is that
pathogenic bacteria that reside in the nose and throat
area are eliminated or greatly reduced in numbers.
This reduces the chances of calves becoming clinically
ill with bacterial pneumonia. Bacteria are the only
agents that are impacted by mass medication. The
spread of viruses and viral infection will not be
impacted. In outbreak situations when mass medication
has been used and response to antibiotic therapy in
sick cattle is poor, then a primary viral component is
likely to be responsible.
Effective treatment of BRD requires planning instead
of reacting. The following points should be
implemented on any cattle operation:
- Treatment
schedules for primary disease conditions need to
be formulated in advance by veterinarians who are
familiar with the operation. The treatment
schedule should include a therapy, length of
treatment, dosage for each drug, route of
administration, size of needle if necessary, site
of injection, and withdrawal time.
- High
risk animals may need to spend time in sick pens.
This reduces the stress of competition within the
pen for fresh feed, water and space. Recovery pens
also may allow for smoother retreatment procedures
at timed intervals.
- Consider
revaccination in problem pens. Underlying viral
infection can result in illness rates greater than
5% per day, and response rates to first time
antibiotic therapy of 80% or less.
Prevention
Prevention of BRD requires proper planning and
careful attention to herd health management. There are
only two ways to prevent and control outbreaks of
infectious disease, 1) break the disease cycle or 2)
alter immunity of the herd. Risks of BRD outbreaks can
be reduced by:
- Developing
a proper pre-weaning vaccination procedure
(vaccinating two to three weeks prior to weaning,
followed by booster vaccinations at weaning).
- Purchasing
source-verified cattle from herds with a known
health history.
- Weaning
cattle and acclimating them to eating from a bunk
prior to shipment.
- Reducing
stresses related to shipping and handling cattle.
- Eliminating
commingling of cattle from various sources at
weaning and shipment.
- Observe
freshly weaned calves or new arrivals at the lot
several times daily. Watch cattle closely for
signs of sickness.
- Isolate
sick cattle in a separate pen.
- Develop
a sound nutritional program for incoming cattle
which will ensure that cattle adapt easily to
eating from a feed bunk. Poor nutrition can
compromise the animal's ability to fight disease.
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