EFFECTS OF ARRIVAL MEDICATION WITH TILMICOSIN PHOSPHATE ON HEALTH ANDPERFORMANCE OF NEWLY RECEIVED BEEF-CATTLE

Three trials were conducted to evaluate delete ate the use of tilmicos in phosphate (Micotil(R)) as a prophylactic medication for newly recei ved, 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 w ith Micotil decreased (P <.01) the percentage of calves treated for sy mptoms of bovine respiratory disease from 46.4 to 0%. In Trial 2, 117 calves (average initial BW = 198 kg) were shipped from Tennessee and a llotted 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 recei ving period. Treatment of calves with Micotil at the time of arrival p rocessing did not affect (P >.50) daily gain during the trial; however , as in Trial 1, mass treatment with Micotil decreased (P <.01) the pe rcentage of calves treated for respiratory disease from 46.4 to 0%. In Trial 2, 117 calves (average initial BW = 191 kg) were shipped from T ennessee 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 tim e 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 rand omly to the same two treatments used in Trials 1 and 2 or to a third t reatment that consisted of administration of Micotil at arrival proces sing if the rectal temperature of the calf was greater than or equal t o 39.7 degrees C. Treatment at arrival processing with Micotil, whethe r on a mass basis or based on rectal temperature, increased daily gain during the initial 28-d receiving period (P <.01) and a subsequent 28 -d feeding period (P <.07). Dry matter intake was greater (P <.05) and feed:gain ratio was lower (P <.03) for both groups of Micotil-treated calves than for control calves for the overall 56-d trial. Both mass treatment (11.9%) and rectal temperature-based treatment (12.9%) of ca lves with Micotil decreased (P <.01) the percentage of calves treated for respiratory disease compared with controls (43.6%). Micotil seems to be a highly effective prophylactic medication for newly received be ef cattle that have been subjected to shipping stress. Application of Micotil based on rectal temperature of calves at the time of processin g was as effective as mass treatment.