American Dexter Cattle Association


Considerations for Responsible Cow Health Planning
by Robert S. Seddon ADRN

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

 


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