Disease occurrence can have a large impact on the economics of a cow/calf operation. The cost of some - like scours or abortions - are obvious. Other diseases, such as those caused by bovine leukosis virus infection, early Johne's infections or bovine virus diarrhea (BVD) shedders, are much less apparent.

But apparent or not, the impact can be devastating in time and money for treatment, reduced performance, increased culling rates, decreased sale value and increased testing expenses.

How can cow/calf operators protect themselves? One answer may be "biosecurity," a term that refers to a program or plan designed to prevent disease by following three principles:

* Prevent the introduction of infected animals,

* Increase the overall and specific resistance to infectious disease,

* Minimize exposure to infectious disease.

Cow/calf operators should consult with their veterinarians to implement such a program designed to minimize the impact of disease causing agents. Here's how it works:

Preventing Infection Introduction It's virtually impossible to keep all pathogens from entering a cow/calf unit, but certain diseases can be kept from entering the herd. Preventing the introduction of infected animals is one.

Either raising your own replacement heifers or purchasing them from known sources is critical. This also applies to bull purchases.

Producers purchasing cattle from other sources need information about the overall disease incidence, specific disease incidence and vaccination history. When that information is incomplete, then testing for information on certain diseases, at least 30 days' quarantine and some vaccination may be necessary. Disease causing agents of concern include Johne's, BVD and bovine leukosis virus.

Raise The Resistance Level Raising the overall level of resistance combines proper genetic selection, proper nutrition and minimizing stress. For example, calving difficulty may predispose a calf to disease. Large birthweight calves can be stressed and often don't consume enough colostrum or absorb the immunity in the colostrum needed to provide protection against disease.

Nutrition of the cow is also a biosecurity issue by ensuring the healthfulness of the cow, the fetus and the calf. The major goal of cow nutrition programs is to minimize feed costs while maintaining adequate body condition for reproduction and lactation at critical times of the year.

Finally, steps should be taken to minimize stress to the cows and calves whenever possible. This can include matching the needs of the cattle to the environment and available resources.

For example, avoid calving seasons that have extremely stressful weather - the heat of summer in the South, and winter storms in the North. Environmental stressors like rain and snowstorms can be minimized by changing the traditional early spring calving season to a season (late spring or fall) that will allow more space/cow and more favorable environmental conditions.

Raising Specific Levels Of Resistance Vaccines are used to increase specific resistance. Choice of vaccinations depends on the exposure risk. Vaccines may be necessary for brucellosis, leptospirosis, campylobacteriosis ("vibriosis"), infectious bovine rhinotracheitis (IBR), BVD, clostridial diseases, scours and perhaps trichomoniasis.

Vaccines should be stored and administered according to label recommendations. Don't assume people know how to properly handle and administer vaccines. A few minutes spent in training is worthwhile.

Timing of vaccination is critical. It takes several days to weeks, and sometimes multiple doses, for an animal's immune system to respond to a vaccine. So, vaccination must occur before disease exposure.

It's important to remember that there is no one vaccination program for all situations. Producers should consult with their veterinarian for a program tailored for their herd. Again, all purchased cattle should have history of vaccination schedules and a list of specific products used.

Minimize Exposure To Pathogens Minimizing herd exposure to disease causing pathogens is important. From a practical standpoint, animals and humans will never be free from exposure to microorganisms.

To implement this principle will require many actions including:

* All animals that show evidence of contagious disease should be isolated from other animals and a diagnosis should be pursued. Any animal that dies should be disposed of in accordance with state regulations. Regulations may allow commercial rendering, burial on site or even composting.

* Rectal sleeves and injection needles must be changed often and in some herds on every animal. This minimizes the risk of transfer of pathogens such as anaplasmosis to an entire group.

* Contamination of feed sources, water sources, bunks and equipment must be minimized. For example, do not use the same equipment for feed and manure handling. In addition, all sources of feed, especially purchased (outside) sources, should have accountability (paper trail).

* Insect, feral animal and bird control programs may be necessary to reduce exposure.

* Veterinarians, other professionals, truckers and visitors should be required to bring clean boots, clothing and vehicles to the farm. This principle is important not only in terms of keeping infectious disease off the farm, but also for minimizing the spread of the disease within the population.

Louis Perino, DVM, is a professor of immunology, health and management at West Texas A&M University in Canyon. Gerald Stokka is an associate professor and Extension beef veterinarian at Kansas State University in Manhattan.