When it comes to health and performance of beef calves received in the feedlot, pre-shipping medication programs are no more effective than arrival medication programs using tilmicosin phosphate. So say researchers at New Mexico State University's Clayton Livestock Research Center.

When the percentage of cattle treated for BRD is low, arrival time is the optimum time to administer medications en masse, researchers say.

In the first of two experiments, researchers treated 96 steers with tilmicosin phosphate (TP) either before shipping, upon arrival or not at all. The percentage of steers treated for BRD decreased for animals treated with TP (control - 71.9%, preshipping - 45.2%, and arrival - 46.9%). The week that calves were treated for BRD differed as well.

In the second experiment, 240 steer and bull calves were treated with or without chlortetracycline, in addition to being treated with TP either before shipping, upon arrival or not at all.

In that experiment, the number of calves treated for BRD decreased for steers treated with TP and for those treated upon arrival (control - 40%, preshipping - 18.7%, and arrival - 7.5%). Averaged across days, serum concentrations of immunoglobulin decreased for steers treated with TP.

Neither of the experiments noted any differences among the treatments in ADG, daily dry matter intake, or gain:feed ratio for the overall receiving period.

For more information contact Glenn Duff at 505/374-2566 or e-mail gduff@nmsu.edu.