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 admin- istration 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: jugu- lar vein or hepatic portal circulation. Experiment 1 was performed in 18 calves randomly assigned to receive intra- jugular infusion of saline (CONIV), or 107 (FUSOIV7), 109 (FUSOIV9), and 1011 (FUSOIV11) of F. necrophorum. In experiment 2, 20 calves were assigned to receive intrapor- tal infusion of saline or 106 (FUSOPV6), 108 (FUSOPV8), and 1010 (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 exam- ined 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 postchal- lenge. The neutrophil-to-lymphocyte ratio was greater for FUSOIV11 than CONIV and FUSOIV9 on d 7 postchallenge. In experiment 2, inoculation increased monocyte and neutrophils counts in the FUSOPV8 group compared with calves in other groups. Implications and Applications: Contrary to previ- ous reports, intraportal and intrajugular inoculation with F. necrophorum did not produce liver abscesses in preru- minant calves. Further research is necessary to explore alternative methodologies to use preruminant calves in experimental disease models for liver abscesses in cattle.