Evaluating the inoculation of four different bacterial pathogens on the development of liver abscesses in beef × dairy crossbred heifers

Abstract Our objective was to assess liver abscess (LA) prevalence in beef × dairy heifers subjected to individual intraruminal bacterial inoculations of F. necrophorum subsp. necrophorum, subsp. funduliforme, Trueperella pyogenes, or Salmonella enterica serotype Lubbock to further understand their etiological roles in LA formation. Beef × dairy heifers (n = 40, initial BW = 126 ± 1.1 kg) were assigned randomly to 1 of 4 treatments: FN = F. necrophorum subsp. necrophorum alone; FF = F. necrophorum subsp. funduliforme alone; TP = T. pyogenes alone; or SL = S. enterica serotype Lubbock alone. Heifers received two doses of 100 mL inoculum consisting of ∼1.0 x 109 CFU/g mL each. Heifer was the experimental unit. Feed disappearance and hematology measurements were analyzed as repeated measures. The model included fixed effects of treatment, sampling day, and treatment × sampling day interaction, with heifer nested within treatment as the subject of the repeated measure. Differences in the percentage prevalence of gross pathology scores among treatments were analyzed as binomial proportions with treatment as a fixed effect. Prevalence of LA was 10, 0, 0, and 0% for FN, FF, TP, and SL, respectively, and did not differ among treatments (P = 1.00). No differences among treatments were observed for rumenitis, lungs, colon, or ileal scores (P ≥ 0.38). While no difference among treatments was observed (P = 0.95), an abundance of LA scars across treatments were recorded (38%). While prevalence was lower than expected, FN was the only treatment to present with an active LA at harvest. The abundance of LA scars across treatments warrants further investigation as timeframe for LA formation and resolution are not fully understood.