title: Field study of the comparative efficacy of gamithromycin and tulathromycin for the control of undifferentiated bovine respiratory disease complex in beef feedlot calves at high risk of developing respiratory tract disease.
abstract: OBJECTIVE
  To compare the efficacy of gamithromycin with that of tulathromycin for control of undifferentiated bovine respiratory disease complex (BRDC) in feedlot calves.
  
  
  METHODS
  2,529 weaned crossbred beef calves.
  
  
  METHODS
  At each of 2 feedlots, calves at risk of developing BRDC were administered a single dose of gamithromycin (6.0 mg/kg, SC; n = 1,263) or tulathromycin (2.5 mg/kg, SC; 1,266) metaphylactically. Health (BRDC morbidity, mortality, case-fatality, and retreatment rates) and performance (average daily gain, dry matter intake, and feed-to-gain ratio) outcomes were compared between treatments via classical hypothesis testing. Bioequivalence limits for gamithromycin and tulathromycin were established for outcomes for which no significant difference between treatments was detected.
  
  
  RESULTS
  Mean BRDC morbidity rate (31.0%) for calves administered gamithromycin was greater than that (22.9%) for calves administered tulathromycin; otherwise, health and performance did not differ between treatments. Limits for mean differences within which gamithromycin was considered bioequivalent to tulathromycin were ± 10% for BRDC retreatment rate, ± 3.5% for BRDC mortality rate, ± 16% for case-fatality rate, ± 37 kg for final body weight, ± 0.1 kg/d for average daily gain, ± 0.3 kg/d for dry matter intake, and ± 0.7 for feed-to-gain ratio.
  
  
  CONCLUSIONS
  The efficacy of gamithromycin did not differ from that of tulathromycin for all outcomes except morbidity rate; calves administered gamithromycin had a higher BRDC morbidity rate than did calves administered tulathromycin. On the basis of the bioequivalence limits established for this dataset, gamithromycin was considered equivalent to tulathromycin for the control of BRDC.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Siddartha
authors.initials: S
authors.lastname: Torres
authors.forename: Dan U
authors.initials: DU
authors.lastname: Thomson
authors.forename: Nora M
authors.initials: NM
authors.lastname: Bello
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Nosky
authors.forename: Chris D
authors.initials: CD
authors.lastname: Reinhardt
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D048090:Bovine Respiratory Disease Complex / Q000517:prevention & control*; D002417:Cattle; D004187:Disaccharides / Q000494:pharmacology*; D006571:Heterocyclic Compounds / Q000494:pharmacology*; D006799:Housing, Animal; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D012307:Risk Factors
chemical_list: D000900:Anti-Bacterial Agents; D004187:Disaccharides; D006571:Heterocyclic Compounds; D018942:Macrolides; C485204:tulathromycin; C552399:gamithromycin