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Before we can talk about vaccinations and if or if not to employ them in
your breeding program, we first need to understand how the immune system
works and what types of immunity are and how we get them. This is the
first in a series of articles that I hope will cover the entire topic
reasonably, so I call it “Immunity 101”.
I am sure that we have all heard the good old “We have a closed herd,
and don’t do anything at all” approach to this topic, and I really need
to wonder about it. If you NEVER buy a cow or calf, and NEVER sell a
calf from your herd, this holds somewhat true, but how many of us can
really say this? Even if you never vaccinate, your bovines will gain a
level of immunity to the normal bacteria that exist in their environment
as their own immune system will generate antibodies as they are exposed
to them.
What about a deer or two running through your field and
exposing them to Hoof and Mouth Disease or another new strain of
pathogenic organism? What about a fly landing on the eye orbit of a cow
with pink eye, and then traveling up to three or more miles to land on
your cows eye? (Flies can travel up to three miles on their own, but
what if they are transported in a stock trailer or truck?) These are all
scenarios that we need to evaluate and make decisions about as we
formulate a responsible health care plan for our herds. It only takes
one outbreak of something to quarantine and destroy what you have spent
a lot of your energy and life to build.
The immune system is a part of the animals lymphatic system that deals
with the production of Lymphocytes, Monocytes and Phagocytes
(Macrophages) that protect the animal from foreign bacteria and viruses
by producing antibodies, mounting a cellular level attack on the foreign
bodies and by Phagocytosis (Engulfing and eating the foreign cell or
virus).
Natural Immunity is a genetic predisposition present in the body at
birth, which is not dependant on previous exposure to a pathogenic
organism to produce antibodies or to mount a response from the immune
system. Dexter cattle as a breed seem to be blessed with a strong
natural immunity that will assist in warding off many of the usual
calfhood problems that are evidenced in many other production breeds.
Acquired Immunity comes in two types, active and passive, and is the
main part of what this article will deal with.
Acquired Active Immunity is gained through exposure to the disease and
the resultant production of antibodies against it, or through
vaccination with a modified or half dead pathogen or toxin that
stimulates the lymphocytes to produce antibodies against it without
actually getting the disease. Obviously, the second way to get active
immunity is preferable.
Acquired passive immunity is what one gets by injecting antibodies
produced in another animal into the diseased animal, This type of
immunity is deployed when immediate protection is needed such as
immunoglobulins given to a very sick child, or antitoxins to treat a
snake bite. Acquired passive immunity is also applied by passage of the
immune bodies through the mother’s placenta before birth and through
ingestion of colostrum in the first 12 hours after birth. (After the
first 12 hour window, the semi permeable membranes in the calf’s
intestines and GI tract change to a state where these antibodies can no
longer be absorbed into the calf.) This passive immunity is powerful,
but short lived, as the calf has no mechanism to produce more of the
antibodies as they wear out over time (about 6 to 8 months on the
passive immunity from the colostrum) and this is where the acquired
active immunity from vaccination should be applied, as the calf will
make the antibodies itself and gain the mechanism to continue to produce
them.
With this information in mind, one next needs to construct a biosafety
profile for their own farm. Each farm has its own set of circumstances
and farm practices to deal with, and I will only cover a few here.
Low Level Biosafety: No animals are brought in as replacements or
for breeding, and the nearest bovine facility is over 25 miles away. No
other farms equipment will be used or brought on to the premises. Few or
no visitors.
Mid Low Biosafety Level: Only a few animals are brought into the farm
over a year, but have full vaccination and health papers before
entering. New animals are quarantined for 4 weeks before exposing them
to the herd, and are evaluated by a professional vetinary before
release. An occasional stock trailer is brought in to deliver or take
animals out of the farm.
Mid Level Biosafety: 5 or more cows/steers/bulls are transported onto
the farm over a year, all incoming animals are fully vaccinated with
health papers from a vetinary, no quarantine is used for the incoming
animals. Other farms equipment is in use, and there are other bovine
facilities within 5-10 miles.
High Level Biosafety: 10 or more animals change hands per year on the
farm, vaccination records of the incoming are incomplete or non
existent, stock auction activity is common, many visitors and
trailers/equipment are coming and going, heavily populated bovine area.
My farm is in the Mid Low Biosafety category, and due to that fact I
need to form a vaccination plan for my animals. I have said nothing
about if you sell a calf or two, as from what I have seen many run on
the “Buyer Beware” principle. Even if there are no diseases on your
farm, that calf is going out into the cold dark night with no pajamas on
if he is not vaccinated, as he might have natural active immunity
against what is on YOUR farm, but what about where he is going to? Many
buyers are new to cattle and not aware of these considerations when they
first buy a calf, and I have heard more than a few bad tales about the
outcomes. All of our calves are sold with a full set of vaccinations and
a full set of boosters after a month, full health papers from our
vetinary, and transfer to the new owner paid for in the sale price.
The next installment on this series will deal with taking the Biosafety
Levels and designing a vaccination plan that suits your own farm and
conditions.
Please remember that this is an over simplified presentation of this
topic, and I would appreciate any comments or suggestions to try to make
this easier to understand and educational.
Robert Seddon
Olde Towne Farm
Mineral, VA
email me
(540) 894-5571 |
