97 Comparison of Tulathromycin and Gamithromycin as Metaphylactic Treatment on Growth Performance, Morbidity, and Treatment Cost in High-risk, Newly Received Beef Calves

Abstract Metaphylactic treatments are used in cattle enterprises to mitigate bovine respiratory disease (BRD). Crossbred beef calves (n = 78; BW = 272 ± 25.8 kg) were randomly assigned 1 of 2 metaphylactic treatments. Upon arrival, calves were processed (ear tagged, vaccinated, dewormed, ear notched) and administered either 1.2 mL/50 kg BW of tulathromycin with a 7-d post-metaphylactic interval (PMI) or 2 mL/50 kg BW of gamithromycin with a 5-d PMI. Cattle were observed daily for signs of morbidity and a Clinical Attitude Score (0 [normal] to 5 [morbid]) was recorded. Calves that scored a 1 or greater and PMI eligible were pulled and rectal temperatures were recorded; if temperature exceeded 40°C, calves were given enrofloxacin. If calves were pulled a second time and criteria met, ceftiofur was the final antibiotic administered. Performance data and cost analysis were analyzed using the MIXED procedure of SAS 9.4, with repeated measure of day used for performance data. Morbidity and treatment with second antibiotic data were analyzed using the GLIMMIX procedure of SAS 9.4. There were no differences in morbidity (P = 0.17) or treatment with second antibiotic (P = 0.32). There was no treatment × day interaction or main effect for treatment for BW or ADG, but there was a main effect of day as BW increased (P < 0.001) through the sampling period and gain from days 0 to14 was greater than gain from days 14 to 28 (P = 0.001) and 28 to 42 (P < 0.001). Initial antibiotic costs ($32.73 vs. $21.74) and overall costs ($32.74 vs. $24.16) were greater (P < 0.001) in cattle administered tulathromycin compared to gamithromycin treated calves. While there were no differences between antibiotic treatments for health or performance, these data indicate that gamithromycin was a more cost-effective metaphylactic treatment for newly received, high-risk calves.