Injecting Fusobacterium necrophorum into the peripheral circulation or hepatic portal vein of preruminant Holstein calves failed to induce liver abscesses

Objective: Our goal was to determine whether administration of Fusobacterium necrophorum ssp. necrophorum into the jugular or portal vein will induce liver abscesses in preruminant calves. Materials and Methods: The study was performed as 2 experiments according to the inoculation site: jugular vein or hepatic portal circulation. Experiment 1 was performed in 18 calves randomly assigned to receive intrajugular infusion of saline (CONIV), or 10 7 (FUSOIV7), 10 9 (FUSOIV9), and 10 11 (FUSOIV11) of F. necrophorum. In experiment 2, 20 calves were assigned to receive intraportal infusion of saline or 10 6 (FUSOPV6), 10 8 (FUSOPV8), and 10 10 (FUSOPV10) of F. necrophorum. Blood samples were collected on d 0, 1, 3, 5, 7, and 14 for hematology. Calves were slaughtered 14 d after inoculation and examined for liver gross pathology. Results and Discussion: Neither model produced liver abscesses. However, in experiment 1, inoculation increased monocyte counts in FUSOIV11 calves versus CONIV, FUSOIV7, and FUSOIV9 on d 3 and 5 postchallenge. The neutrophil-to-lymphocyte ratio was greater for FUSOIV11 than CONIV and FUSOIV9 on d 7 postchal lenge. In experiment 2, inoculation increased monocyte and neutrophils counts in the FUSOPV8 group compared with calves in other groups. Implications and Applications: Contrary to previous reports, intraportal and intrajugular inoculation with F. necrophorum did not produce liver abscesses in preruminant calves. Further research is necessary to explore alternative methodologies to use preruminant calves in experimental disease models for liver abscesses in cattle.