Development of an experimental model for liver abscess induction in Holstein steers using an acidotic diet challenge and bacterial inoculation.

Autor:	McDaniel ZS; Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX, USA., Hales KE; Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX, USA., Salih H; College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA., Deters A; College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA., Shi X; College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA., Nagaraja TG; College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA., Lawrence TE; Department of Agricultural Sciences, West Texas A&M University, Canyon, TX, USA., Tennant TC; Department of Agricultural Sciences, West Texas A&M University, Canyon, TX, USA., Amachawadi RG; College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA., Carroll JA; United States Department of Agriculture, Agricultural Research Service, Livestock Issues Research Unit, Lubbock, TX, USA., Burdick Sanchez NC; United States Department of Agriculture, Agricultural Research Service, Livestock Issues Research Unit, Lubbock, TX, USA., Galyean ML; Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX, USA., Smock TM; Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX, USA., Ballou MA; Department of Veterinary Sciences, Texas Tech University, Lubbock, TX, USA., Machado VS; Department of Veterinary Sciences, Texas Tech University, Lubbock, TX, USA., Davis E; Department of Veterinary Sciences, Texas Tech University, Lubbock, TX, USA., Broadway PR; United States Department of Agriculture, Agricultural Research Service, Livestock Issues Research Unit, Lubbock, TX, USA.
Jazyk:	angličtina
Zdroj:	Journal of animal science [J Anim Sci] 2024 Jan 03; Vol. 102.
DOI:	10.1093/jas/skae046
Abstrakt:	Holstein steers (n = 40; initial BW = 84.9 ± 7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorum subsp. necrophorum (9.8 × 108 colony forming units [CFU]/mL), Trueperella pyogenes (3.91 × 109 CFU/mL), and Salmonella enterica serovar Lubbock (3.07 × 108 CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P ≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P ≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorum subsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorum subsp. necrophorum and Salmonella. The F. necrophorum subsp. necrophorum was clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophorum into the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA. (Published by Oxford University Press on behalf of the American Society of Animal Science 2024.)
Databáze:	MEDLINE
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