Comparison of Bovine Transfer Factor and Tilmicosin Phosphate: Effects on Health and Growth Performance of Newly Arrived Feedlot Heifers

Two experiments were conducted to evaluate bovine transfer factor (TF) for use in receiving cattle. In Experiment 1,665 crossbred beef heifers initially weighing 225 kg were used in a completely randomized design to determine the effects of bovine TF on the health and performance of beef cattle during a 36-day receiving period. During initial processing, heifers received either a subcutaneous injection of tilmicosin phosphate at 10 mg/kg of body weight or an oral drench which provided 700 mg of TF isolated from bovine colostrum. Heifers given bovine TF during initial processing received an additional 700 mg of bovine TF per day in the diet between day 2 and 5. Heifers were monitored for clinical signs of undifferentiated bovine respiratory disease (UBRD), and heifers exhibiting signs of UBRD received antibiotic therapy. In experiment 2, rumen fluid was incubated with casein or with bovine TF and was analyzed for in vitro NH3-N and total amino acid-N concentrations, which were used to calculate the rate of protein degradation. The percentage of heifers treated once, twice, or three times for UBRD was greater for heifers given bovine TF than for heifers given tilmicosin phosphate. During the 36-day receiving period, there were no differences between bovine TF and tilmicosin phosphate with respect to dry-matter intake, average daily gain, or gain efficiency of heifers. The rate of in vitro protein degradation was greater for bovine TF than for casein. Orally administering bovine TF as a prophylactic treatment against UBRD in cattle is not as effective as prophylactic medication with tilmicosin phosphate, possibly because of extensive degradation of bovine TF protein by rumen microflora.