Evaluation of an endotoxin challenge and intraruminal bacterial inoculation model to induce liver abscesses in Holstein steers

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, VINICIUS - Texas Tech University; Broadway, Paul

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2023
Publication Date: 7/22/2023
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., Broadway, P.R. 2023. Evaluation of an endotoxin challenge and intraruminal bacterial inoculation model to induce liver abscesses in Holstein steers. Journal of Animal Science. 101. Article skad 242. https://doi.org/10.1093/jas/skad242.
DOI: https://doi.org/10.1093/jas/skad242

Interpretive Summary: Liver abscesses in feedlot cattle can result in decreased feed intake, average daily gain, gain efficiency, and hot carcass weight. Presence of liver abscesses in cattle after harvesting increase liver condemnations, carcass trimming, and decrease quality grade with an estimated economic cost to packers of $41.6 million per year. Models that induce and describe the origins of liver abscess are difficult to develop. Development of a repeatable model to study the origin of liver abscesses would be valuable to the entire beef industry. Scientists in Lubbock, Texas and university partners evaluated giving endotoxin followed by bacteria common to liver abscesses in order to develop a model to elucidate the origin of liver abscesses. Data from this study suggest that giving endotoxin in combination with bacteria common to liver abscesses is not a viable model to induce liver abscesses. However, the length of time needed to induce liver abscesses is unknown in steers that are dosed with bacteria common to liver abscesses. Developing a non-invasive model that induces liver abscesses in cattle remains an important research challenge. These data will be of interest to researchers in the area of cattle nutrition and physiology.

Technical Abstract: Holstein steers (n = 40; initial BW = 96.0 ± 10.5 kg) were individually housed in a climate-controlled barn for 8 or 15 d to evaluate potential models for the genesis of liver abscesses (LA). Steers were randomly assigned and balanced by BW to 1 of 2 treatments: 1) intravenous saline injection followed by intraruminal bacterial inoculation with Fusobacterium necrophorum subsp. necrophorum (1 × 109 colony forming unit [CFU]/mL) and Salmonella enterica serovar Lubbock (1 × 106 CFU/mL; CON; n = 20 steers); or 2) intravenous injection with 0.25 µg/kg body weight (BW) of lipopolysaccharide (LPS; Escherichia coli O111:B4) followed by intraruminal bacterial inoculation of F. necrophorum subsp. necrophorum (1 × 109 CFU/mL) and S. enterica serovar Lubbock (1 × 106 CFU/mL; LBI; n = 20 steers). Body weights were recorded on d -4, -1, 3, and 10, and blood was collected for hematology on d -4, 3, and 10, relative to LPS infusion on d 0. Intraruminal bacterial inoculation occurred on d 1. Ten steers from each treatment group were harvested on d 3 or 10 to perform gross pathological examination of the lung, rumen, liver, LA if present, and colon. The 2 × 2 factorial arrangement of treatments with or without LPS infusion over 2 harvest dates relative to intraruminal inoculation was analyzed in PROC GLIMMIX of SAS as repeated measures over time with individual steer as the experimental unit. The model included main effects of treatment, time, and their interaction. Steer nested within treatment was the subject of the repeated measures. Feed disappearance was less for LBI than CON (P < 0.01); however, BW did not differ (P = 0.33) between treatments. Neither treatment nor time differed for hematology (P = 0.13), and no gross pathological differences were noted in the lung, liver, LA, or colon (P = 0.25). A treatment × harvest date interaction was noted for ruminal pathology in which LBI had an increased percentage of abnormal rumen scores on d 3 (P < 0.01). These results suggest that an LPS challenge in combination with intraruminal bacterial inoculation of pathogens commonly isolated from LA was not sufficient to induce LA in steers within 3 or 10 d. Further evaluation is needed to produce a viable model to investigate the genesis and prevention of LA in cattle.