Validation of an experimental model to induce liver abscesses in steers using an acidotic diet challenge and intraruminal bacterial inoculation

Authors: MCDANIEL, ZACH - Texas Tech University; HALES, K - Texas Tech University; NAGARAJA, T - Kansas State University; LAWRENCE, TY - West Texas A & M University; TENNANT, TRAVIS - West Texas A & M University; AMACHAWADI, RAGHAVENDRA - Kansas State University; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; GALYEAN, MICHAEL - Texas Tech University; DAVIS, EMILY - Texas Tech University; KOHL, KESLEY - Texas Tech University; LINE, DALTON - Texas Tech University; DORNBACH, COLTON - Texas Tech University; SALIH, HARITH - Kansas State University; DETERS, ALYSSA - Kansas State University; SHI, XIAORONG - Kansas State University; BALLOU, MICHAEL - Texas Tech University; MACHADO, VINICIUS - Texas Tech University; SMOCK, TAYLOR - Texas Tech University; Broadway, Paul

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2023
Publication Date: 6/1/2024
Citation: McDaniel, Z.S., Hales, K.E., Nagaraja, T.G., Lawrence, T.E., Tennant, T.C., Amachawadi, R.G., Carroll, J.A., Sanchez, N.C., Galyean, M.L., Davis, E., Kohl, K.B., Line, D.J., Dornbach, C.W., Salih, H., Deters, A., Shi, X., Ballou, M.A., Machado, V.S., Smock, T.M., Broadway, P.R. 2024. Validation of an experimental model to induce liver abscesses in steers using an acidotic diet challenge and intraruminal bacterial inoculation. Applied Animal Science. 40(3):398-413. https://doi.org/10.15232/aas.2023-02485.
DOI: https://doi.org/10.15232/aas.2023-02485

Interpretive Summary: Liver abscesses in beef cattle are of great concern within the industry. The frequency of liver abscesses can range from 0 to 70% at harvest with the average being 12 to 32% of fed cattle. The economic impact is about $400 million loss annually. Scientists as the USDA-ARS, along with university partners, conducted a study to determine the repeatability of a model to produce liver abscess in dairy calves. The study used diet changes over time and dosed calves with bacteria common to liver abscesses. Results from this study confirmed the model can produce liver abscesses in dairy calves. This repeatable model will be useful in the future for studying ways to reduce and explain the development of liver abscesses. These results will be of interest to scientists studying liver abscesses, and cattle producers.

Technical Abstract: Our objectives were to determine the repeatability of a model to induce liver abscesses in cattle while simultaneously exploring the roles of Fusobacterium necrophorum and Salmonella enterica in liver abscess formation and severity. Holstein steers (n = 40; initial BW= 110 ± 12.0 kg) were randomly assigned to 1 of 4 treatments: 1) control diet (CON; n = 10); 2) acidotic diet (AD; n = 10); 3) acidotic diet plus intraruminal inoculation of Fusobacterium necrophorum subsp. necrophorum (8.81 × 108 CFU/mL; ADF; n = 10); or 4) acidotic diet and intraruminal inoculation of F. necrophorum (8.81 × 108 CFU/mL) and Salmonella enterica serotype Lubbock (1.52 × 109 CFU/mL; ADFS; n = 10). Beginning on d 0, steers were subjected to 4 acidotic cycles in which steers were fed the acidotic diet for 3 d and then switched to the control diet for 2 d. Beginning on d 21, steers in AD, ADF, and ADFS remained on the acidotic diet for the remainder of the study. Ruminal pH boluses were randomly inserted into 20 steers that recorded ruminal pH in 15-min intervals before being averaged into 6-hr time intervals. Euthanasia occurred on d 38, and gross pathological observations on the lung, rumen, liver, and colon were recorded. No pathological differences were noted in lung (P = 0.44) nor colon scores (P = 0.32) among treatment groups; however, ruminal damage was more severe in ADF and ADFS than CON and AD (P = 0.05). Liver abscess prevalence was 40% in ADF and 50% in ADFS vs. 0% in CON and AD (P < 0.01). The acidotic diet alone caused mild ruminal acidosis but did not result in LA formation. Nonetheless, the acidotic diet in conjunction with intraruminal bacterial inoculation increased the severity of rumenitis and resulted in LA. These results agree with previous studies and suggest that this model is repeatable. An acidotic diet with intraruminal inoculation of bacteria is a viable model to study the formation of LA and possible mitigation methods.