Tend-R-Leen: The original no-roughage feeding program

Disease of the respiratory tract is a major problem for cattle that continues to cause serious economic

losses for producers. Bovine respiratory disease (BRD) causes increased death losses as well as medication costs, labor, and lost production. Many different infectious agents may cause similar clinical signs. Multiple agents are often involved in the development of BRD.

Iowa State University Research

A retrospective study of 2,146 feedlot cattle in 17 feedlot tests from 1988 to 1997 was conducted to determine the impact of bovine respiratory disease (BRD) on veterinary treatment costs, average daily gain, carcass traits, mortality, and net profit. Morbidity caused by BRD was 20.6%. The average cost to treat each case of BRD was $12.39. Mortality rate of calves diagnosed and treated for BRD was 5.9% vs. .35% for those not diagnosed with BRD. Average daily gain differed between treated and non-treated steers during the first 28 days on feed but did not differ from 28 days to harvest. Net profit was $57.48 lower for treated steers. Eighty-two percent of this difference was due to a combination of mortality and treatment costs. Eighteen percent of the net profit difference was due to improved performance and carcass value of the non-treated steers.

Data from 496 steers and heifers in nine feedlot tests were used to determine the effects of age, weaning, and use of modified live virus or killed vaccines prior to the test to predict BRD. Younger calves, non-weaned calves, and calves vaccinated with killed vaccines prior to the test had higher BRD morbidity than those that were older, weaned, or vaccinated with modified live virus vaccines, respectively. Treatment regimes that precluded relapse resulting in re-treatment prevented reduced performance and loss of carcass value. Using modified live virus vaccines and weaning calves 30 days prior to shipment reduced the incidence of BRD.

Disease Conditions (or Syndromes)

The respiratory diseases of cattle can be divided into three main categories:

1. Upper Respiratory Tract Infections - these infections cause inflammation of the nostrils, throat (pharynx) and windpipe (trachea). The clinical signs are usually mild and involve coughing, nasal discharge, fever, and a decreased appetite.

2. Diphtheria - this infection involves the larynx (voice box) and may occur alone or along with other respiratory infections. There are often loud noises during breathing. The swelling may severely restrict the air flow, causing death.

3. Pneumonia (Lower Respiratory Tract Infection) - an infection of the lungs is often due to an extension of infection from the upper respiratory tract or a failure of the mechanisms that are designed to protect the lungs. This is much more serious, and causes more severe signs than does an upper respiratory infection. Shipping fever is one form of lower respiratory tract disease. It derives its name from the fact that it usually occurs shortly after shipment of the cattle.

Causes and Development of Disease

The causes of BRD are multiple and complex, but the three factors of stress, viral infection, and bacterial infection are almost always involved in cases of severe disease. A wide variety of different stressors and agents may be involved in the disease process.

Some of the viral agents produce only mild clinical signs by themselves, but they may cause severe signs and death when combined with other viral or bacterial agents and stress. Many normal cattle carry one or more of the bacterial and viral agents in their upper respiratory system with no ill effects. These often enter the lungs, but are usually expelled or inactivated. However, under stress, the animal’s defense mechanisms may be overcome, and the infection established, resulting in BRD.

The mixing of cattle from different sources and wide environmental temperature fluctuations have been identified as major factors in the initiation of disease outbreaks in feedlots.

The most common signs of BRD are nasal and eye discharges, coughing, fever, decreased appetite, varying degrees of breathing difficulty and noise, rapid breathing, depression, droopy ears, and open-mouthed breathing. These vary greatly, depending on the stage and extent of the disease process.

In the past, there have been no drugs effective against viral agents in the treatment of cattle for respiratory disease. Through current research, some products may become available for use in the future. The antibiotics and sulfas have no effect on the viral agents, but are often of great aid against the bacterial invaders.

Treatment of BRD will be effective and the death loss minimal if the following principals are practiced:

Cattle that have had over 50 percent of the lung tissue damaged before effective treatment is started will have a poor response, many relapses, and a high mortality rate.

Group (or mass) treatment may, in some situations, help to reduce the number of cattle severely affected with BRD. It can also delay use of more effective, individual treatment and result in a greater loss. It is preferable to include the antibiotic or sulfa in the drinking water rather than the feed, since the sick cattle quickly go off feed but usually continue to drink water a little longer.

The two major areas to emphasize for prevention are management and vaccination. Of the two, management is usually much more important.

Evaluate all the possible causes for stress on the cattle, and determine which ones can reasonably be eliminated or at least reduced. Look carefully at alternative methods of operation and at specific timing of processing, vaccinating, etc. Recognize that the critical period for disease detection is the 3 weeks immediately following weaning, placing on feed, or shipping of cattle. Avoid mixing (commingling) cattle from different sources during this highly critical 3-week period. Preconditioning does reduce the rate of illness and death, but this practice must be evaluated in terms of economic costs and benefits for the specific producer involved. Arrange the pens and feeders to keep new cattle close to the feed and water supplies. Don’t overcrowd, especially early in the feeding period. Control the dust and mud.

Vaccines are available for several infectious diseases of cattle. However, with the various brand names as well as different combinations available, the choice of vaccines can become very complicated.

Calves vaccinated under 6 months of age should generally be revaccinated after that age to provide a longer lasting immunity. It is important to follow the specific directions provided with a vaccine. If two doses are recommended initially, don’t count on very much protection until 7 to 14 days after the second dose has been given.