Using antibiotic properly cuts pneumonia deaths



I’ve got a stocker operation in Falls County and this winter I lost more calves to pneumonia than I can remember.


I know it was a cold winter, but too many calves died after I gave them strong antibiotics. Can you give me some tips on how to use these antibiotics better?


Sure I can give you some guidelines for treatment of calves with pneumonia. First, I would like to discuss the risk factors that affect both the amount of pneumonia in a group of calves as well as the success rate in treatment of pneumonia cases.


The beef cattle industry’s biggest disease problem is infectious bronchopneumonia, commonly called the bovine respiratory disease (BRD) complex.


Factors affecting treatment success


The number of factors and interactions between factors that affect the occurrence of pneumonia and survival or death of affected calves make even disease researchers dizzy! The factors that affect success of treatment fall into three general categories: severity of disease, degree of resistance of the calf and how properly antibiotics are given.


Severity of disease depends mainly on susceptibility of the calf, virulence of the infectious agents (viruses, bacteria, mycoplasma), and amount of exposure.


Resistance of the calf is determined by its plane of nutrition, level of parasitism and degree of stress in its environment (general health), age, genetics and amount of specific immunity from vaccination. Proper administration of antibiotics depends on starting treatment early with an antibiotic that is effective, giving the correct dose and treating for a long enough number of days.


It’s easy to see that using a strong antibiotic is just one piece of a complex puzzle. Thinking over how the various pieces apply to your calves this past winter will help you to understand why you had a lower than usual success rate in treating pneumonia.


A bird’s eye view of your calves in their pasture could point to management practices that will lower the number of pneumonia cases next winter and increase treatment success in calves that do get pneumonia.


Are your calves parasitized? Is there shelter such as wind breaks in your pastures? Have your calves been vaccinated against respiratory pathogens? Are your calves young and small?


Metaphylactic antibiotic treatment


If your calves are light-weight and have an uncertain vaccination history, they would be classified as high-risk. Giving a dose of long-acting antibiotic on arrival to calves that have a high likelihood of breaking with pneumonia is called metaphylaxis. As a rule of thumb, this will reduce the number of cases of pneumonia in high-risk calves by 50 percent.


All calves are treated with antibiotics on arrival because it’s not possible to identify which calves will become ill. Some calves in early stages of pneumonia will be stoic and other calves that do not have pneumonia will look sick from the fatigue of transportation.


It’s just tough to pull sick calves accurately.


In a study involving 469 steers followed to slaughter, 35 percent were treated for pneumonia. Of the 35 percent treated, 78 percent had lung lesions at harvest indicating prior pneumonia. However, 68 percent of the steers never treated for pneumonia also had lung lesions at harvest.


Calves with lung lesions had 0.13 lbs less daily gains than calves without lung lesions. This illustrates that death losses are not the only negative financial impacts of pneumonia. Steps to prevent pneumonia can be very cost-effective.


Therapeutic antibiotic treatment


The 5 basic principles of successful antibiotic treatment of pneumonia in calves are start treatment early, treat with an effective antibiotic, give the proper antibiotic dose, treat long enough and avoid residues at slaughter.


Our present arsenal of miraclemycin antibiotics make it relatively easy to select an effective antibiotic and follow label directions on proper dosage and avoidance of residues.


These broad-spectrum antibiotics all are very effective. In addition, many of them maintain lung tissue concentrations for five days or more which is an adequate duration of treatment for pneumonia. Starting treatment early is dependent on a rancher’s acumen in spotting the clinical signs of calves in the beginning stages of pneumonia.


Some people may think that the most important key to successful treatment of calf pneumonia is selection of the proper antibiotic.


All of us seem enthralled by each new antibiotic and our numerous choices.


Many more calves, however, have died because antibiotic treatment was started too late than use of an ineffective antibiotic. If damage to lung tissue is extensive and walled-off when treatment is started even the most potent antibiotic will be helpless.


A calf with the classical signs of pneumonia will have labored breathing, ocular and nasal discharges, depression, appear gaunt and possibly have a soft low cough. The big problem is that starting antibiotic treatment in that calf may be too late to save its life. There may be too much lung damage by then.


Successful treatment of pneumonia involves pulling calves displaying the very earliest signs of depression. I got a lot of practice spotting calves in early stages of pneumonia in three clinical studies involving calves shipped over a thousand miles from Tennessee. It’s best to start by observing calves from a distance. Cattle are prey animals that for their own protection become alert even if sick when approached.


Calves in the early stages of pneumonia will stand off by themselves with a dropped head and arched back. Some have droopy ears and sleepy, partly closed eyes. They will move slowly and may drag their toes. Feeding is a good time to check for sick calves. They may slowly walk up to feed or not come up at all. Some calves come up to feed, but back out after a few nibbles. These can be found by checking 15 minutes after feeding to see if all calves that came up are still eating.


Pull suspect calves and confirm your diagnosis by rectal temperature. Treat calves with a rectal temperature of 104 F or greater. That is treatment based on depression with undifferentiated fever (no specific signs of pneumonia like nasal discharge yet).


Mass antibiotic treatment


New cases can be limited in a severe pneumonia outbreak by treatment of all calves in the pasture with one of the long-acting antibiotics recommended for metaphylactic treatment. The rules of thumb commonly used by veterinarians for mass treating a pasture of calves breaking with pneumonia are to act when 10 percent of the group were treated for two or three consecutive days or when 25 percent needed treatment in a single day. I don’t think anyone would call that being trigger-happy with antibiotics.


Bottom line


Very early treatment is critical for successful treatment of pneumonia in calves. It’s far more important than which antibiotic is used. It’s automatic when antibiotics are used in metaphylactic or mass medication schemes. Early treatment of individuals depends on keen observations of animal behavior by ranchers and boils down to treatment based on depression with undifferentiated fever. Be sure to consult your veterinarian for recommendations on specific drugs and dosages that are best for each of the three above uses of antibiotics.


Antibiotics can reduce deaths and poor weight gains due to pneumonia, but it takes more than antibiotics to control this devastating disease. Management practices that reduce or eliminate the risk factors of pneumonia will prevent pneumonia outbreaks and have a greater financial benefit than treatment of pneumonia cases.


As my old boss in practice, Dr. Douglas, used to say: Preventive medicine is the best medicine.

• Dr. Steve Wikse is a retired professor of large animal clinical sciences in the College of Veterinary Medicine and Biomedical Sciences at Texas A&M University.

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