Calves most often become sick following stressful situations such as weaning or marketing. The clinical signs are usually seen 7-21 days after the calves are bought, but can occur anywhere from 2-30 days after purchase. Less frequently, calves that have not been marketed or weaned can develop pneumonia, usually related to weather changes or other stressors.
The most common and earliest recognizable clinical sign of pneumonia is depression. Calves exhibiting depression will have drooping ears, an extended head, a bowed back and/or often isolate themselves from other cattle. As these calves get progressively sicker, they will go off feed and will exhibit an increased respiratory rate. Increased lung sounds can be heard with the aid of a stethoscope. A thermometer is another useful tool in the diagnosis of pneumonia. Most sick calves will have a fever of 104°-108°F. However, temperatures can be falsely elevated in the afternoon due to increased outside temperatures. In order to obtain the most accurate temperature reading for an animal that is suspected to be sick, the calf's temperature should be taken before 10:00 am.
Developing a Treatment Protocol
There are four primary questions to be answered when developing a treatment protocol:
When do I treat the calf?
Early treatment of calves is the most important aspect of a successful treatment program. Therefore, calves should be observed often and when any of the clinical signs listed previously are detected, the animal's temperature and breathing sounds should be analyzed.
What will help this calf?
Aside from antibiotics, sick calves should be given excellent quality hay and grain. Grass and/or rye are also good feedstuffs as sick calves will often eat these when they will not eat anything else. Unless the weather is severe, calves often benefit from sunlight and being outside as opposed to being in a barn with poor ventilation.
Individual Calf - A sick calf's temperature, appetite, and attitude should be monitored after treatment. If the calf shows no improvement over 24-48 hours, consideration may be given to switching antibiotics.
Herd - A producer should consult a veterinarian when deciding whether or not to change antibiotics for the entire herd. In order for the veterinarian to make a good recommendation, he/she will need to know the case fatality rate (the number of treated calves which have died) and whether or not these animals died less than 48 hours or greater than 48 hours after treatment. For this reason, it is important to keep accurate treatment records.
Mass Medication, also called Metaphylaxis, is the treatment upon arrival of an entire group of calves at high risk for respiratory disease. There is little data on the economics of using mass medication in Virginia stocker calves. In order for the process to be economical, a producer would need to expect greater than 30% of the calves will get sick. Some factors to consider when deciding to mass medicate are:
Season - Calves are more likely to get sick in the fall than any other time of the year.
Weaned vs. Unweaned - Calves that are not weaned when marketed are much more likely to get sick.
Weight - Calves weighing less than 450 lbs. are more likely to get sick and the expense of mass medication will be less as well, due to the smaller body weight.
Sex - Calves that must be castrated after marketing are more likely to contract BRDC.
Weather - Adverse weather probably plays the single largest role in the likelihood of a large number of calves becoming sick. It is often difficult, however, to predict weather patterns for the first two weeks after the calves are purchased.
History of Disease - The past history of the source of the calves as well as that of your own farm should be considered.
Goals of the Operation - If the producer's goal is to treat and lose as few cattle as possible, then mass medication may be the best, though perhaps not the most economical, method.
Source: John F. Currin and W. Dee Whittier, Extension Specialists and Professors, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech
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