by: Soren Rodning, DVM, MS, DACT
Associate Professor & Extension Veterinarian,Auburn University Department of Animal Sciences

Many of you will have calves arriving soon, either as newborns or stocker calves, and despite all the advances in health management, some calves will still get sick. When this happens, work with your veterinarian to quickly identify the problem, develop a treatment plan, and implement steps to prevent the spread of disease to other animals.

Preventing Disease Transmission

Keep it simple when it comes to preventing the spread of infectious diseases. There are only five ways infectious diseases can spread: aerosol, direct contact, fomite or traffic, oral, and vector transmission. What this means is that you don't have to remember all the details about a particular disease to keep it from spreading, you just need to understand the five routes of infectious disease transmission so you can implement simple, practical steps to prevent it.

1. Aerosol transmission occurs when disease agents contained in droplets pass through the air from one animal to another. Close proximity of infected and susceptible animals is typically required for this type of disease transmission.

2. Direct contact transmission of disease agents occurs when a susceptible animal directly touches an infected animal or its open wounds, mucous membranes, blood, saliva, nose-to-nose contact, rubbing or biting.

3. Fomite transmission occurs when a disease pathogen is carried or spread from one animal to another by an inanimate object (such as boots, buckets, dirty clothes, needles, tattoo pliers, castration and grooming equipment, etc.). Vehicles and trailers can also be considered fomites and spread disease through traffic transmission.

4. Disease agents can also spread through oral transmission, such as when an animal licks or chews on contaminated environmental objects or consumes contaminated feed or water.

5. Vector-borne transmission involves the spread of disease through an insect such as ticks, mosquitoes, flies, etc.

Respiratory Disease

Newly arrived stocker calves are particularly susceptible to respiratory disease. Quickly identifying sick calves and providing prompt treatment increases the likelihood of restoring calf health. When treating calves, be sure to maintain records that identify the animal, treatment, and date so you can monitor treatment outcomes and adhere to drug withdrawal times. In addition, keep the following in mind when treating calves this year.

Proper dosing

Effective treatment of calves with respiratory disease or any infectious bacterial disease is dependent, in part, on administering a proper dose of antibiotic based on an accurate body weight. Under-dosing heavier calves will reduce product efficacy, resulting in increased re-treatments, chronically ill calves, and calf deaths. Overdosing lighter calves can potentially result in toxicity and the need for extended withdrawal times prior to sale, not to mention the unnecessary, additional expense of the excess antibiotic.

Use a weight scale in the processing chute to ensure medication doses are based on accurate body weights. While a scale is no small investment, it is one that will help pay for itself over time as a result of more effective treatments resulting in healthier calves, as well as directly lowering medicine costs by preventing overdosing. Newer generation, long-acting antibiotics typically cost between $2.50 and $5.00 per 100 pounds of calf treated. While these antibiotics are very effective in treating sick calves, overdosing can quickly become extremely expensive. In addition, weighing calves prior to routine practices such as deworming not only gives you a baseline for measuring product effectiveness, but also prevents costly overdosing. Injectable dewormers usually cost between $0.30 and $0.70 per milliliter (mL), so overdosing 500 calves with just one extra mL per animal costs about an extra $250 that could have been invested in a scale.

Treatment intervals

Some older cattle antibiotics were only active for about 24 hours, so frequent administration was sometimes critical to successful treatment with these short-acting antibiotics. However, many of today's antibiotics work for much longer than 24 hours, and in some cases may be active for up to 14 days. As a result, many antibiotics are now labeled for single-dose therapy. When using these long-acting antibiotics it is important to observe proper post-treatment intervals before re-treating with the same product or a different product. Sometimes that is easier said than done as it is difficult not to become impatient when you don't see a rapid improvement after treating sick cattle with an antibiotic. The temptation is to then re-treat the animals after just a couple days with a different product, even though the original product is active for much longer and the calf just needs a little more time to heal. Premature retreatment wastes medicine and causes undue stress that could actually hinder the animal's recovery. It also puts more than the recommended level of antibiotic in the animal's system at one time. The best practice is to treat sick animals and then allow them to recover for the length of time the antibiotic is active.

Label directions

Always follow product label directions and your veterinarian's instructions when administering medications to cattle. While it is best to refer directly to a product label or prescription, hanging a sign near the working chute with current dosages, route(s) of administration, storage recommendations, and withdrawal times based on label directions for commonly used medications provides a reference in the event the product label is worn or smeared or otherwise hard to read. Ideally, the sign should have dosages in an easy to use format such as mL per a predetermined amount of body weight (for example, 4.5 mL per 100 pounds of body weight). Nobody wants to be converting dosages from mg/kg to mL/body weight after the animal arrives in the chute. Most newer product labels have dosages based on mL per 100 or 110 pound body weight intervals, but if not, go ahead and make that calculation before going to the processing chute to treat calves.

Discuss disease prevention and treatment protocols with your veterinarian before calves arrive this fall to optimize herd health. Your veterinarian plays an important role - preventing, diagnosing, and treating disease. The first step in selecting the proper treatment for an infectious disease depends on accurately diagnosing the problem, and our veterinarian can assist in that process.

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