Effects of arrival medication with tilmicosin phosphate on health and performance of newly received beef cattle1

Three trials were conducted to evaluate the use of tilmicosin phosphate (Micotil) as a prophylactic medication for newly received, stressed beef cattle. In Trial 1, 57 beef calves (average initial BW = 170 kg) were shipped to the research feedlot from Tennessee and either given no antibiotic at processing or treated with Micotil at 10 mg of tilmicosin phosphate/kg of BW. During a 28-d receiving period, treatment at processing with Micotil did not affect daily gain (P < .17) or DMI (P < .22) compared to control calves. Prophylactic treatment with Micotil decreased (P < .01) the percentage of calves treated for symptoms of bovine respiratory disease from 46.4 to 0%. In Trial 2, 117 calves (average initial BW = 191 kg) were shipped from Tennessee and allotted randomly to the same two treatments as in Trial 1. All calves grazed a 24-ha pasture of irrigated winter wheat during the 28-d receiving period. Treatment of calves with Micotil at the time of arrival processing did not affect (P > .50) daily gain during the trial; however, as in Trial 1, mass treatment with Micotil decreased (P < .01) the percentage of calves treated for respiratory disease from 32.8% to 12.1%. In Trial 3, two truckloads of beef calves (183 total; average initial BW = 232 kg) shipped from Tennessee were allotted randomly to the same two treatments used in Trials 1 and 2 or to a third treatment that consisted of administration of Micotil at arrival processing if the rectal temperature of the calf was > or = 39.7 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)