Monday, October 1, 2001

New & Old Antibiotic Selection Concerns


The cattle feeding industry is a highly specialized, efficient means of beef production; however, because the industry transports cattle over great distances, congregates them in confined areas, and exposes them to a concentrated energy ration, we see a complicated bovine respiratory disease syndrome. Despite the knowledge of the veterinarian, know-how and skill of pen riders and hospital crews, bovine respiratory disease complex (BRDC) remains the cattle- feeding industry’s number-one disease challenge.

1.) Preventative Medicine
a.) Pre-Arrival
b.) Arrival
2.) Nutrition
3.) Environmental Management
4.) Personnel Management
5.) Hospital Management
a.) Therapeutic Management
b.) Records Management

The objective of the receiving program is to ensure that incoming cattle acclimate to the finishing period as efficiently and atraumatically as possible. The typical feedlot handles cattle from extremely divergent backgrounds with widely varied nutritional experience and immunologic status. A small management error in this starting/receiving period can be greatly magnified.
The management of BRDC is not as simple as we would like or expect it to be. Clinical evaluation upon on arrival will alert feedlot personnel to potential problems. Subjective data should include origin, weight, type of cattle, length of transport, season of the year and ambient weather conditions. Objective data would include per-cent shrink, classical respiratory signs and number of visibly sick animals.
Cattle are routinely classified into risk categories:
1.) High Risk-exposed
No history of vaccination, sale barn/auction market origin and usually considered "put-togethers" com-mingled.
Morbidity normally occurs first week following arrival.
2.) High Risk-unexposed
No history of vaccination; however, usually one source origin.
Morbidity usually occurs after typical 7-10 day incubation period and normally sees an 18-21 day break. These can be difficult and require a re-vaccination.
3.) Low Risk
History of vaccination for BRDC and weaned for minimum of 30 days.
Low risk vaccination program which is usually only a booster.
The processing of cattle includes those procedures and medications deemed necessary to maximize performance and minimize health-related losses. The actual act of processing most commonly occurs upon arrival; however, in order to circumvent some of the shortcomings processing after exposure to disease causing factors; alternative approaches need to be examined.
Clostridia diseases, internal and external parasites, and BRDC account for a majority of the monetary losses due to high morbidity, high medication, poor performance or death.

Choosing an appropriate treatment program and its success depends equally upon the management of both healthy and sick cattle and the choice of medicines.
Antibiotics are used both from a treatment and preventative standpoint in processing programs. Antibiotics can be utilized effectively in the preventative area but four common mistakes can be encountered. First, timing of antibiotic administration may be too early (bacterial infection not occurring) or too late (extreme damage already present to internal organs) to effect a response. Secondly, the amount of antibiotics given is not enough to ensure significant bacterial control. Thirdly, improper administration of an effective product may also result in inadequate response. Lastly, combinations or "cocktails" of antibiotics can render the ingredients inactive and cause other quality assurance residue concerns.
The goal for each animal entering the hospital for treatment should be a lasting cure (minimum repull per cent). Achieving that means accurate and specific identification of the disease; proper evaluation and treatment; and re-evaluation prior to leaving the sick pen.
When data from feedyards is summarized, 7.2 percent of cattle received treatments for various reasons of which 83 percent during seasonal peaks of this total morbidity is attributed to BRDC.The key to successfully manage BRDC is the feedlot’s management health team, headed by the veterinarian, ability to formulate a comprehensive health program, which consists of:
Majority of pen the riders are capable to spot animals just as they are breaking with pneumonia. Animals’ exhibiting signs such as:
The first and foremost rule of a hospital and therapeutic program is to pull early, pull appropriately, and treat aggressively (easier said than done). If sick animals are not pulled from the pen before respiratory disease has become an advanced problem; medication response will generally be very poor. This corresponds to the latter stages of the incubation period of disease and is before the animal actually shows classical clinical signs of disease.
-Loss of appetite,
-Stiff gait/soreness when walking,
-Crusty muzzle,
-Mild diarrhea,
-Rapid, shallow breathing,
-Moist cough,
or a combination of these signs or symptoms should be pulled for evaluation and treatment. Acutely affected animals respond best to treatment, and animals treated earlier in the course of the disease have a better chance of recovering
-Eye and/or nasal discharge,. Animals must be pulled for sickness appropriately. If sick animals are not managed properly then these animals will not get the hospital care they need, hospital pens will become overcrowded, and the hospital crew will needlessly become overwhelmed. Heavy pulls don’t always coincide with proper pulls.
To treat aggressively in the feedyard means that when an animal is pulled initially for BRDC he is treated with an antibiotic program based on input from the feedyard’s veterinarian that will stop pnemoumia at its earliest stage of development, and not allow further progression of the disease process. These will effectively decreases total treatment days, decrease the number of retreatments, and prevent high death losses.
Antibiotic selection can be done by antemortem testing, postmortem testing, clinical response evaluation, and with properly designed field studies. Clinical response rate evaluation is best tool for treatment of BRDC.

If using an antibiotic that requires daily administration, treatment of sick animals should be continued for at least three successive days. Depending upon the antibiotic, this can be accomplished with one injection or administration or with three successive days of treatment. This rule is important in order to decrease total number of treatment days, number of treatments, and the number of pen deaths after treatment.

Treatment should include antibiotics as well as other medications that are supportive in nature. Supportive care includes such drugs as B-complex vitamins to stimulate an appetite and replenish body loss, antihistamines to open swollen, narrowed airways, and electrolytes to replace body fluid loss as well as electrolyte loss.
All drugs used in beef cattle have a specific purpose and use. It is important that the feedyard health crew be well versed on the proper use of drugs used in the treatment of sick animals. A drug used improperly is sometimes worse than no medication at all.

Hospital treatment records are essential for calculating:
  1. First Therapy Response
  2. Relapse Rate
  3. Case Fatality Rate
  4. Chronic Rate
5.) Weight Gain/Loss
According to the University of Nebraska’s Great Plains Veterinary Education Center, sick calves gaining more than 5 percent of their body weight while in the hospital pen had a repull rate of only 3 percent; whereas, those losing weight had a repull rate of 34 percent.
  1. Cost of Treatment
When evaluating records and treatment response risk classification, age of animals, morbidity patterns and season of the year must be considered.
Achieving a lasting cure involves teamwork from everyone on the feedlot’s health team. From a pen rider’s ability to identify sick calves, to a hospital crew’s evaluation and treatment decisions, with the knowledge and skill of the feedlot’s veterinarian and capability to communicate with the feedlot personnel will have a tremendous impact on the bottom line. The more informed and capable its members, the better equipped they’ll be to make accurate, profitable care decisions and the more likely sick animals will achieve a lasting cure.
The last rule of treatment is keeping of clear and accurate records. These records should not only provide bookkeeping services but also allow to adequately assessing treatment response.