Investigation of a Reduction in Tylosin on the Prevalence of Liver Abscesses and Antimicrobial Resistance in Enterococci in Feedlot Cattle

Frontiers in Veterinary Science

Cassidy Klima¹  Sherry J. Hannon¹  Ana L. Bras¹  Calvin W. Booker¹  Claudia Narvaez-Bravo²  Argenis Rodas-Gonzalez²  Tim McAllister³  Taylor Davedow³  Rahat Zaheer³  Haley Sanderson³  Sheryl Gow⁴ 

[1] Feedlot Health Management Services, Okotoks, AB, Canada;Food and Human Nutritional Sciences Department, University of Manitoba, Winnipeg, MB, Canada;Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada;Public Health Agency of Canada, Saskatoon, SK, Canada;

关键词: Enterococci;    antimicrobial resistance;    tylosin;    erythromycin;    tetracycline;    beef cattle;   

DOI  :  10.3389/fvets.2020.00090

来源: DOAJ

【 摘 要 】

Recent concerns over linkages between antimicrobial resistance in human pathogens and antimicrobial use in livestock have prompted researchers to investigate management strategies that reduce the current reliance on in-feed tylosin to control liver abscesses in feedlot cattle. A total of 7,576 crossbred yearlings were allocated to the study (~253 animals/pen, 10 replicate pens per treatment) and individually randomized to one of three treatments. Tylosin phosphate (11 ppm) was included in-feed (1) for the first 125 days on feed (DOF) (FIRST-78%), (2) for DOF 41 to 161 (LAST-75%), or (3) for the entire feeding period (CON; day 0–161). Fecal composites were collected from the pen floor on days 0, 81, and 160 of the finishing period. Serial dilutions were spread plated for enumeration of enterococci on Bile Esculin Azide (BEA) agar and BEA amended with 8 μg/ml erythromycin. Results indicated that although the proportion of EryR enterococci increased with DOF (P < 0.01), neither treatment (P = 0.34) or treatment × DOF (P = 0.37) affected antimicrobial resistance. Of the 538 isolates, 97% were enterococci, with mixed species isolated early in the feeding period and only Enterococcus hirae isolated at the end. Isolates were most frequently resistant to tylosin (86%), erythromycin (84%), and doxycycline (31%). Macrolide and tetracycline resistant isolates harbored erm(B), msrC, and tet(L), tet(M), tet(O) genes, respectively. Overall, the proportion of EryR enterococci increased (P < 0.05) in all three treatments over the feeding period. Compared to the control cattle, FIRST-78% cattle had more severe (P < 0.05) liver abscesses, while there was a trend (P < 0.08) for this response in LAST-75% cattle. There was no difference (P > 0.05) in total liver abscesses, growth performance, carcass traits, morbidity, or mortality among treatments. These results support the potential to reduce the duration and therefore quantity of tylosin administered to feedlot cattle during the feeding period without impacting animal productivity.

【 授权许可】

Unknown