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Bethany Lovaas, DVM
University of MInnesota Beef Team
As we near the end of the summer months, we all should
start thinking about the next steps in the cow production
cycle: pregnancy diagnosis and weaning.
Weaning is the most stressful time in a calf’s
life, because calves will often experience several significant
changes at one time. Some of these changes include dietary
changes (milk/pasture to hay/concentrate), weather changes
(warm/dry to cold/wet), and social changes (pasture to
no more mom/dry lot). The ideal situation would be to
make only one change at a time, however, this is sometimes
A few possible solutions would be to start making changes
on the pasture. Depending on the production system, creep
feeding the calves might reduce the stress of dietary
changes. Ideally, if possible, the calves could be left
on the pasture, and the cows kept in the dry lot, or
on a separate pasture. Weaning earlier in the year, before
the weather turns cold and wet, is a good way to get
around environmental stress. Also, the uses of some types
of anti-nursing devices have been able to significantly
reduce the stress of weaning. These are some options
to consider, each producer should evaluate his/her production
system to determine what specific stress-relieving changes
can be made. Consult with your herd veterinarian on weaning
strategies, as well as vaccination recommendations.
Why is stress is the most important challenge to overcome
when weaning calves? Stress causes the release of the
hormone, cortisol, from the adrenal gland. Cortisol is
a “catabolic steroid” that has negative effects
on the immune system. This immunosuppression not only
makes a calf more susceptible to respiratory disease,
but it also decreases the calf’s ability to respond
to a vaccine. So, even though you may have given the
calf a shot, the calf may not be protected because its
immune system was unable to respond to the vaccine. Because
of this, it is important to get the first dose of vaccine
into the calves while they are still nursing, when stress
levels are low.
Bugs to Beat
Viruses: IBR, BVDV, PI 3, BRSV
should receive a vaccine against these viruses. Alone,
these viruses will cause significant disease. However,
they rarely act alone. The viruses compromise the calf’s mechanical defenses in the trachea and
lungs, which allows the bacteria to overgrow. This results
in a bacterial pneumonia that can leave the calf with
permanent damage to lung tissue, and decrease the calf’s
ability to grow. This will result in poor performance
in replacement heifers and bulls and poor growth and
carcass performance in steers.
Bacteria: Pasteurella sp., Manhemmia
sp., Histophilus sp. (formerly Hemophilus)
against the bacterial respiratory pathogens is usually
only necessary in cattle that are destined to go into
a feedlot. These vaccines vary in efficacy and often
their utility depends on the situation. If you have a
problem, or anticipate having a problem with one of these
bacteria at weaning, it may be prudent for you to consider
using a vaccine containing a respiratory bacterial component.
Some retained ownership programs (i.e. U of M Carcass
Merit Program) and custom feeders may require that calves
be vaccinated against these bacterial pathogens before
they are received into the feedlot.
Clostridia: (tetanus, blackleg, botulism, overeating
disease, redwater, etc.)
Most vaccines against clostridial
organisms are very efficacious and usually one dose will
impart life-long immunity. If, however, you live in an
area or region that has significant problems with a clostridial
organism, it may be prudent for you to vaccinate more
often than once a lifetime. Most of us can get away with
one dose, with administration of a booster in high risk
situations (i.e. bull calves castrated using a band/banding
device should receive a tetanus vaccination at the time
If you are retaining replacement
heifers, or selling breeding stock, it would be wise
to vaccinate against leptospira.
The lepto component of a lot of the combination vaccines
usually is not very efficacious, and does not provide
complete protection. However, vaccinating against lepto
is better than doing nothing. If you have tested your
herd, and found that you have a problem with Leptospira
hardjo subsp. bovis, you may want to consider using
the Spirovac vaccine. It is a fairly expensive vaccine,
and therefore should be used in cases of known infection.
An interesting finding (recently published in BEEF magazine)
indicated that there is an interaction between the IBR
portion of a modified live vaccine and the Manhemmia fraction
of a vaccine. If a calf has never been vaccinated before,
and the two are given to a calf at the same time, the
calf will not develop an effective immunity against Manhemmia.
Therefore, a calf that you thought was protected against
this bacterium actually isn’t.
In order to get around this issue, the Manhemmia vaccine
should be given at least 2 weeks after the modified live
IBR vaccine. This ensures that the calf’s immune
system has responded to the IBR and is ready to take
on the Manhemmia vaccine.
Modified live vs killed vaccines:
It is my opinion that there is no reason why a modified
live vaccine should not be used on nursing calves. Some
producers are concerned about causing abortions in the
cows if the nursing calves are vaccinated with a modified
live vaccine, but the risk for such an event is miniscule.
Modified live vaccines will provide better protection
against the viral respiratory pathogens because they
will stimulate two different populations of immune cells
(CD4 + and CD8 + T cells), whereas a killed vaccine will
only stimulate one of these populations (CD4 + t cells).
Also, in regard to killed vaccines, research indicates
that there is strong interference with the vaccine by
maternal antibodies from the cow’s colostrum, and
maternal antibodies can hang around in the calf’s
circulation for up to 6 months. Therefore, you are not
likely to gain a good response from a killed vaccine
until after the calf is of weaning age.
Proper handling of vaccine is important for the maintenance
of its efficacy. Expiration dates should be checked before
use, and vaccine should never be allowed to reach room
temperature before use. It is also a good practice to
keep the vaccine out of direct sunlight. Ultraviolet
rays will likely kill a large number of viruses in a
modified live vaccine. By covering, or providing shade
for multidose syringes when not in use, you will be able
to minimize UV damage to the vaccine before you get it
into the calf. Because there are actually living viruses
in the vaccine, the efficacy of the vaccine is dependant
on the survival of those viruses.
For any further information on this topic, please feel
free to contact us by accessing our website at (www.extension.umn.edu/beef).