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Title: EFFECTS OF TILMICOSIN PHOSPHATE ADMINISTERED PRIOR TO TRANSPORT OR AT TIME OF ARRIVAL AND FEEDING OF CHLORTETRACYCLINE AFTER ARRIVAL IN A FEEDLOT ON MANNHEIMIA HAEMOLYTICA IN NASAL SECRETIONS OF TRANSPORTED STEERS

Author
item Frank, Glynn
item DUFF, GLEN - NEW MEX.ST.UNIV.,CLAYTON

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: A common management practice to reduce the incidence of pneumonia in cattle is to treat them with tilmicosin, an antibiotic, when they arrive at the feedyard. This practice has been successful, but study of its effect has been limited to reduction of clinical cases of disease. In this study, prophylactic treatment with the antibiotic also cured nasal colonization of fcattle by a bacterial pathogen which is the major cause of pneumonia. This is important because treatment reduces the numbers of disease carriers during a time when cattle are most susceptible to infection.

Technical Abstract: The object of this study was to determine the effect of premedication with tilmicosin, comparing the time of premedication (preshipment or on arrival) on the incidence of respiratory tract disease (RTD) and on colonization of the nasopharynx of calves with PH after transport. Four loads of calves (total n = 454, approximately 200 kg) were assembled and processed in order buyer barns in MS and AR. For each load, 1/3 received tilmicosin phosphate pre-shipping, and all were transported to a feedyard in NM, arriving the next day. Upon arrival, 1/3 received tilmicosin. The remaining 1/3 did not receive a scheduled treatment with tilmicosin. Calves were observed daily for signs of respiratory tract disease (RTD). Calves with signs of RTD were given an unscheduled tilmicosin treatment. Nasal swabs were examined for the presence of PH to determine the status of colonization of the nasopharynx. Premedicated calves were given fewer unscheduled treatments for RTD, and had a lower incidence of PH colonization than calves that were not premedicated. The effects of treatment on colonization were evident for up to 6 days. There was no evident advantage between preshipment treatment and treatment on arrival. Premedication with tilmicosin should inhibit the growth of PH in the upper respiratory tract, thus reducing the incidence of pneumonia and reducing spread to other calves. Both effects should reduce the incidence of acute RTD during the 1st week at the feedyard, when transported calves are most susceptible.