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

Authors: MCDANIEL, ZACH - Texas Tech University; HALES, KRISTIN - Texas Tech University; NAGARAJA, T - Kansas State University; LAWRENCE, TY - West Texas A & M University; AMACHAWADI, RAGHAVENDRA - Kansas State University; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; GALYEAN, MICHAEL - Texas Tech University; SMOCK, TAYLOR - Texas Tech University; BALLOU, MICHAEL - Texas Tech University; MACHADO, VINIVIUS - Texas Tech University; DABVIS, EMILY - Texas Tech University; Broadway, Paul

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2023
Publication Date: 11/1/2023
Citation: McDaniel, Z.S., Hales, K.E., Nagaraja, T.G., Lawrence, T.E., Amachawadi, R.G., Carroll, J.A., Sanchez, N.C., Galyean, M.L., Smock, T.M., Ballou, M.A., Machado, V.S., Dabvis, E.M., Broadway, P.R. 2023. Development of an experimental model to induce liver abscesses in steers using an acidotic diet challenge and oral bacterial inoculation. Journal of Animal Science Supplement.

Interpretive Summary:

Technical Abstract: The objective of this study was to develop a model for liver abscesses (LA) in Holstein steers by using an acidotic diet or acidotic diet plus intraruminal inoculation of Fusobacterium necrophorum (Strain: FN-8LI), Salmonella enterica serotype Lubbock, and Truperella pyogenes. Holstein steers (n = 40; initial BW = 84.9 + 7.1 kg) were individually housed and randomly assigned to either a negative control diet (CON), an acidotic diet (AD), or an acidotic diet plus intraruminal inoculation with the bacterial mixture (ADB; 1 × 109 CFU/mL). Steers in AD and ADB were cycled on (3 d) and off (2 d) a high-starch diet 20 days before intraruminal inoculation of ADB. Following inoculation, AD and ADB remained on the acidotic diet for the remainder of the study. Ruminal pH boluses were randomly inserted across treatments to monitor ruminal pH throughout the study. Steers were euthanized and necropsied to record gross pathology on the lung, rumen, liver, and colon. Culture techniques were used to determine the prevalence of each bacterium within LA. The F. necrophorum isolated from LA were phylogenetically profiled to determine the relationship to the strain inoculated. Quantitative polymerase chain reaction methods were used to quantify F. necrophorum in rumen tissue and contents, as well as colon tissue and contents. Data were analyzed as a completely randomized design with animal as the experimental unit, where an a of = 0.05 determined significance. Liver abscess prevalence was 43% in ADB vs. 0% in AD and CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD and 78.6% greater than in CON (P = 0.05). There was a treatment × time interaction for ruminal pH, where pH decreased below 5.6 in AD and ADB calves during each cycle of the acidotic diet (P < 0.01). The ADB contained a greater concentration of F. necrophorum subsp. necrophorum and subsp. fundliforme within rumen tissue (P = 0.03). Of the LA cultured, 100% contained F. necrophorum, 50% S. enterica, and 0% contained T. pyogenes. Following phylogenetic profiling, it was determined that the strain isolated from LA matched the phylogeny of that inoculated. The results of this study suggests that acidotic diet in combination with intraruminal inoculation of the bacterial mixture is sufficient to induce liver abscesses and provides insight on possible mechanisms and origins of LA. Further studies are needed to validate these results and determine if this model may be used to study novel intervention methods.