Evaluating the repeatability of a model for inducing liver abscesses using an acidotic diet and intraruminal bacterial inoculation and exploring the roles of Fusobacterium necrophorum and Salmonella enterica

Authors: MCDANIEL, ZACH - Texas Tech University; ABBASI, MINA - Kansas State University; HALES, KRISTIN - Texas Tech University; NAGARAJA, T - Kansas State University; LAWRENCE, TY - West Texas A & M University; TENNANT, TRAVIS - West Texas A & M University; SHI, XIAORONG - Kansas State University; AMACHAWADI, RAGHAVENDRA - Kansas State University; Sanchez, Nicole; Carroll, Jeffery - Jeff Carroll; GALYEAN, MICHAEL - Texas Tech University; DAVIS, EMILY - Texas Tech University; BALLOU, MICHAEL - Texas Tech University; MACHADO, VINICIUS - Texas Tech University; SMOCK, TAYLOR - Texas Tech University; Broadway, Paul

Submitted to: Proceeding of Plains Nutrition Council Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: We evaluated the repeatability of a model to induce liver abscesses (LA) in steers by feeding an acidotic diet with intraruminal bacterial inoculation of Fusobacterium necrophorum subsp. necrophorum alone or in combination with Salmonella enterica serotype Lubbock. A secondary objective was to evaluate the effects of F. necrophorum alone or in combination with S. Lubbock on the prevalence of LA. Holstein steers (n = 40; initial BW 242 ± 26 lb) were assigned randomly to four treatments: 1) High-forage control diet (CON; n = 10); 2) acidotic diet (AD; n = 10); 3) acidotic diet with intraruminal inoculation of Fusobacterium necrophorum subsp. necrophorum (8.81 × 10^8 CFU/mL/100 mL; ADF; n = 10); 4) acidotic diet and intraruminal inoculation of F. necrophorum subsp. necrophorum (8.81 × 10^8 CFU/mL/100 mL) and Salmonella enterica serotype Lubbock (1.52 × 10^9 CFU/mL/100 mL; ADFS; n = 10). On d 0, steers in AD, ADF, and ADFS were fed the acidotic diet for 3 d, then switched to the control diet for 2 d, this cycle was repeated a total of four times throughout the study. On d 20 steers in ADF and ADFS were intraruminally inoculated with bacteria and fed the acidotic diet for the remainder of the study. Ruminal pH was monitored in 15 min increments for the duration of the study, and the steers were euthanized for pathological examination on d 38. Healthy and abscessed tissues were evaluated using PCR to determine bacterial prevalence of F. necrophorum subsp. necrophorum, subsp. funduliforme, and S. enterica. Rumen scores in ADF and ADFS were 40 and 20% more severe, respectively, compared with AD or CON (0%; P = 0.03). Liver abscess prevalence was greater in ADF (40%) and ADFS (50%) than in CON and AD (0%; P < 0.01). Fusobacterium necrophorum subsp. necrophorum was isolated from 100% of LA in ADF and ADFS, whereas, S. enterica was isolated from 25% and 20% of liver abscesses in ADF and ADFS, respectively. Prevalence of subsp. funduliforme was not detected in abscessed liver tissue. These data suggest that an acidotic diet in combination with intraruminal bacterial inoculation is sufficient to cause rumenitis and liver abscesses. Current results align with previous findings and demonstrate the repeatability of the model, thereby providing opportunities for further investigation into the synergism between F. necrophorum and S. enterica.