Feed Lot

DEC 2018

Feedlots and cow/calf operations in the beef industry who feed 500 or more has annually on grains and concentrates; maintain 500 or more beef cows; backgrounder, stocker/grower, preconditioner; veterinarian, nutritionist, consultant

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8 FEED•LOT December 2018 is often needed to boost the cop- per and selenium levels during the initial arrival period. 3. Metaphylactic treatment (treatment of all calves on arrival) of high risk calves with long-acting antibiotics is a well-established, beneficial procedure that can re- duce morbidity (sickness) and case fatality (death) by up to 50% in high risk calves. Be aware that overconfidence in and reliance on metaphylaxis and long-acting antibiotics can lead to delayed fol- low-up treatment if calves are not adequately monitored. 4. Feed bunks and watering troughs are known areas for disease transmission. Keep sick cattle, es- pecially chronic pneumonia calves, away from healthy calves and man- age the feed and water separately. 5. Eliminating exposure by re- ducing unnecessary traffic through the farm, isolating new arrivals, good sanitation and treating sick cattle early will help reduce the risk of disease spread. 6. Buying preconditioned calves that have been weaned and vac- cinated for respiratory diseases prior to weaning (especially BVD) and dewormed will help minimize sickness and death loss. In summary, the clinical features of disease caused by Histophilus somni are often confused with other diseases commonly seen in the feedlot. Response to antibiotic therapy is frequently very poor due to biofilm protection. Diagnosis in a live calf can be difficult since H. somni is often recovered from na- sal swabs of healthy calves so the presence of the bacteria in the nose of a sick calf does not prove it is causing disease. It is also a difficult bacterium to grow in the laborato- ry, especially if the calf has been recently treated with antibiotics. Future research will focus on the relationship between HS and other respiratory pathogens, developing improved diagnostic tests, moni- toring antibiotic effectiveness and development of new vaccines for prevention of disease. FL 2WKHU0DQLIHVWDWLRQV Arthritis with joint swelling may follow episodes of pneumonia. Middle ear infections with drain- age from the ear canals may also be seen. Diagnosis of Histophilus somni pneumonia in a live calf is chal- lenging because it is present in the upper airways of both healthy and diseased calves so swabs taken from deep in the nose will not tell the story of what is actually hap- pening in the lungs. Only lung fluid removed from the lung via bron- choalveolar lavage can be used for culture or molecular assays such as PCR to identify the organism. The organism is very difficult to grow in the laboratory, especially if the calf was treated with antibiotics, so PCR is strongly recommended for detection. Mixed lung infections with other disease- causing bacte- ria such as Mannheimia haemo- lytica and Pasteurella multocida can easily overgrow Histophilus somni on a culture plate so the identification is easily missed when relying on traditional bacterial cul- ture methods alone. Prevention depends on sound bi- osecurity and biocontainment prac- tices. Because HS pneumonia or septicemia may develop secondary to viral infections (especially BVD) or in combination with other bac- terial pathogens, control should begin with minimizing the effect of well-recognized factors predis- posing to BRD. Stress plays a major role in disease through immuno- suppression so excellent nutrition, sound vaccination protocols and management are critical. There are numerous challenges to production of an effective vaccine to prevent Histophilus somni infections. In spite of all the considerable amount of work on bacterin-based HS vac- cines, there is no direct proof that these vaccines are effective under field conditions. Consult with your local veterinarian for the best man- agement plan for your operation. The following steps should re- duce the risk of pneumonia in feed- er calves: 1. Vaccination with a 5-way re- spiratory virus vaccine and a Mann- heimia haemolytica toxoid. Use of an intranasal vaccine initially for the viral fraction is recommended in high risk cattle to keep appetite up and reduce vaccine-induced fever. 2. Cattle with extremely low blood concentrations of the trace elements selenium and copper have difficulty fighting any disease chal- lenge. An injectable trace mineral supplement (such as Multimin 90) FEEDLOT FOCUS PNEUMONIA... from previous page

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