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Liver abscesses pose a significant economic burden on the beef industry, resulting in substantial profit losses. A contributor to these losses is the decreased productivity and feed efficiency observed in affected cattle. Reduced feed efficiency could be attributed to the impairment of metabolic activity due to liver tissue damage caused by the abscesses. While tissue within the abscess itself is dysfunctional, little is known about the functional state of the surrounding liver tissue. Considering this, the present research aimed to evaluate liver tissue gene expression profiles at varying distances from liver abscesses. Tissue samples (n = 21) were collected from three distinct regions: 1) <4 mm proximal from the abscess without including abscessed tissue (adjacent tissue), 2) 3 cm proximal from the abscess (nearby tissue), and 3) from livers with no abscesses (healthy controls). Gene expression comparisons utilizing DESeq were conducted between each tissue sample group. The number of differentially expressed genes (FDR ≤ 0.10) identified in each comparison is presented in Table 1. Tissue directly adjacent to the liver abscess was substantially different in gene expression when compared with both the healthy and tissue 3 cm proximal to an abscess. Fewer genes exhibited differential expression between healthy tissue and tissue taken 3 cm away. Gene enrichment analysis was conducted using the KOBAS-i software to identify biological pathways associated with the differentially expressed genes. Genes upregulated in liver tissue adjacent to the abscess were associated (FDR ≤ 0.10) with immune response pathways, including the “T cell receptor signaling pathway” and “Cytokine-Cytokine receptor interaction,” whereas downregulated genes were linked to metabolic pathways such as “Fatty Acid Metabolism” and multiple amino acid biosynthesis pathways. Gene expression differences between tissue 3 cm away and healthy tissue were minimal; however, enrichment analysis identified significant (FDR ≤ 0.10) metabolic pathways such as the “peroxisome proliferator-activated receptor signaling” which is involved in gluconeogenesis and lipid metabolism, suggesting some metabolic alterations up to 3 cm proximal from the abscess. Upregulation of immune response pathways and downregulation of metabolic pathways in the adjacent tissue suggest a shift in cellular priorities, diverting resources to combat the active infection rather than routine metabolic processes. This localized immune response and metabolic dysregulation observed in the liver tissue adjacent to the abscess, coupled with metabolic alterations up to 3 cm away, highlight the effects of liver abscesses on the overall metabolic capacity and functionality of the liver. Continued research should focus on investigating the effect of abscess severity on overall liver function. [ABSTRACT FROM AUTHOR]

Liver abscesses (LA) continue to be an economic challenge for the beef industry. Chronic ruminal acidosis and ruminitis contribute to LA development. Fusobacterium necrophorum subsp. necrophorum, a ruminal bacterium, is the primary causative agent. Damaged ruminal, and possibly other gut regions, become susceptible to invasion and colonization by subsp. necrophorum, which reaches the liver via portal blood to cause abscesses. We hypothesize that the LA occurrence is related to the presence and concentrations of subsp. necrophorum in gut contents and epithelial tissues. Our primary objective was to detect, isolate and quantify subsp. necrophorum in gut contents and tissues in steers with experimentally induced LA. An experimental model, which included ruminal acidosis followed by intraruminal inoculation of subsp. necrophorum alone or with Salmonella enterica serotype Lubbock, was used to assess the relationship. Steers (n = 61) from three independent studies with three treatment groups were used. Treatments included: 1) forage-based diet with intraruminal inoculation of subsp. necrophorum; 2) ruminal acidosis with intraruminal inoculation of subsp. necrophorum; and 3) ruminal acidosis with intraruminal inoculation of subsp. necrophorum and S. Lubbock. Steers were euthanized 3 wk after bacterial inoculation and liver, gut contents, and tissue samples (ruminal, ileal and colonic) from steers with LA (n = 27) and with healthy livers (n = 34) were collected and subjected to culture method and quantitative PCR to isolate, detect, and quantify subsp. necrophorum. Data were analyzed by PROC GLIMMIX of SAS after summarizing frequency of isolation in various sample types within each study for steers with and without LA and converted to a binomial proportion. Concentrations were analyzed using steer as the experimental unit. The model included the fixed effect of liver status (abscessed or not) and study as the random effect. The frequency of isolation and mean concentration of subsp. necrophorum in purulent materials of LA were 100% and 3.5 x 107 Log10 CFU/g, respectively. The frequency of isolation of subsp. necrophorum from ruminal tissues of steers with LA was greater than steers with healthy livers (35.4 vs 14.5%; P = 0.04). Likewise, the concentration of subsp. necrophorum in ruminal tissues was greater in steers with LA than with healthy livers (4.2 vs 3.6 Log10 CFU/g; P < 0.001). None of the ileal and colonic tissues, except one ileal tissue in each group, yielded subsp. necrophorum. The concentrations of subsp. necrophorum in ruminal, ileal, and colonic contents did not differ (P = 0.9) between steers with LA or with healthy livers. Our data suggest that the occurrence of LA is positively related to prevalence and concentration of subsp. necrophorum in ruminal tissue, and the colonization likely serves as a source of continuous flow of bacterial emboli into the portal blood to initiate LA development. [ABSTRACT FROM AUTHOR]

Crossbred beef heifers (N  = 1,394; initial shrunk body weight [BW] 291 ± 9.9 kg) were used to investigate the efficacy of 10-G Armor (Life Products, Inc. Norfolk, NE; 10-G) upon feedlot performance, carcass characteristics, and fecal and subiliac lymph nodes Salmonella prevalence. Heifers were blocked by day of arrival and allocated to 1 of 20 pens (N  = 70 heifers/pen) and assigned one of two treatments (10 pens/treatment): no direct-fed microbial (CON) or 2 g/heifer/d of Lactobacillus acidophilus, Enterococcus faecium, Pediococcus pentosaceus, Lactobacillus brevis and Lactobacillus plantarum , respectively (Life Products, Inc. Norfolk, NE; 10-G). Twenty-four animals were randomly selected from each pen for Salmonella sampling. Recto-anal mucosal swab samples (RAMS) were obtained at initial processing and harvest; subiliac lymph nodes were collected at harvest. In addition, pen surface fecal pats were collected and composited by pen (10 pats per composite, 5 composites per pen) on days 0, 52, 120, and 192. Data were analyzed as a generalized complete block design, and pen served as the experimental unit. No differences were observed in live growth performance metrics (P  ≥ 0.55). Yield grade distributions did not differ between treatments (P  ≥ 0.62); however, cattle fed 10-G tended (P  = 0.06; 14.6% vs. 18.9%) to have fewer USDA Select carcasses and more (P  = 0.09; 73.6% vs. 78.0%) USDA Choice carcasses. Cattle fed 10-G tended (P  = 0.10; 9.2% vs. 12.3%) to have fewer liver abscesses and had fewer (P  = 0.04; 5.3% vs. 8.5%) severe liver abscesses. Salmonella prevalence of RAMS did not differ between treatments at initial processing (P  = 0.97; CON = 11.6%, 10-G = 11.5%) or at harvest (P  = 0.91; CON = 99.0%, 10-G = 98.6%); however, RAMS differed (P  < 0.01) in Salmonella prevalence between the two collection times. Cattle fed 10-G had a lower frequency of Salmonella positive lymph nodes (P  = 0.01; CON = 15.8%, 10-G = 7.4%) than CON. However, Salmonella log (mpn/g) of lymph nodes did not differ between treatments at harvest (P  = 0.34; CON = 0.73, 10-G = 0.34). These data indicate that cattle fed 10-G have decreased rates of severe liver abscesses without altering live animal performance or carcass characteristics. Supplementation of 10-G significantly reduced the prevalence rate of Salmonella recovered from the subiliac lymph nodes. The factors responsible for the observed difference in the effects of 10-G on Salmonella warrant further investigation [ABSTRACT FROM AUTHOR]

Liver abscesses (LA) are a polymicrobial infection and the causative agents include two subspecies of Fusobacterium necrophorum, necrophorum and funduliforme, and Trueperella pyogenes. Nucleic acidbased analysis of the purulent material of LA has indicated that Proteobacteria and Bacteroidetes were the dominant phyla, next to phylum Fusobacteria. The sporadic isolations of bacterial species of the Proteobacteria and Bacteroidetes in LA have been reported. An aspect of the pathogenesis that has not been investigated is whether bacterial pathogens in LA originate, besides the rumen, from the colon? Therefore, our objectives were to target detection and isolations of Salmonella enterica, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Bacteroides fragilis, in addition to routine isolations of F. necrophorum and T. pyogenes, from LA and also from ruminal and colonic epithelial tissues of the same animals. Liver abscesses, matched with ruminal and colonic epithelial tissue samples from 96 steers and heifers, originating from 15 feedlots, were collected at slaughter, transported to the laboratory and processed within 24 hours. Samples were subjected to anaerobic and aerobic culture methods, including enrichment and selective media for detection and isolation of S. enterica, E. coli, K. pneumonia, P. aeruginosa, and B. fragilis. Prevalence of bacterial species were shown in table 1. For each bacterium, two-sided Fisher's exact test was used to evaluate the association of its prevalence in LA with that in colon and rumen at 0.05 level. Overall, prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenes and S. enterica in liver abscesses were 86.4% (83/96), 21.8% (21/96), 35.4% (34/96) and 6.2% (6/96), respectively (Table 1). In ruminal tissue samples, prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenes and S. enterica were 6.6% (6/96), 40.6% (39/96), 11.4% (11/96) and 4.1% (4/96), respectively. Prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenes and S. enterica in colonic tissues were 18.7% (18/96), 36.4% (35/96), 0% (0/96) and 7.2% (7/96), respectively. Prevalence of E. coli, Klebsiella spp., and P. aeruginosa in LA samples were 70.8% (68/96), 92.7% (89/96), and 91.6% (88/96), respectively. Prevalence of E. coli, Klebsiella spp., and P. aeruginosa in rumen epithelial tissue samples were 17.7% (17/96), 50.0%, (48/96), and 15.6% (15/96), respectively. Prevalence of E. coli, Klebsiella spp., and P. aeruginosa in colonic tissue samples were 16.6% (16/96), 24.0% (26/96), and 12.5% (12/96), respectively. Prevalence of subsp. funduliforme in ruminal and colonic tissues was greater than subsp. necrophorum. None of the liver abscess samples yielded B. fragilis. In conclusion, E. coli was the second most dominant species detected and isolated from LA, next only to subsp. necrophorum. The greater frequencies of isolations of subsp. necrophorum and S. enterica from colonic epithelial than ruminal epithelial tissues suggest that hindgut could also be a source of pathogens involved in LA. [ABSTRACT FROM AUTHOR]

To address the gaps in current scientific knowledge, the objective of the present study was to investigate the impact of fumonisin exposure on feedlot cattle intake and performance. Fifty steers were received (day 0; 361 ± 6.4 kg), housed individually and fed once daily at 0800 hours. All steers were transitioned to a dry-rolled corn-based finishing diet from days 0 to 21 and then were fed the control finishing diet until day 50. Treatment diets were formulated to achieve ≤5 (CON), 15 (15PPM), 30 (30PPM), 60 (60PPM), or 90 ppm (90PPM) of total dietary fumonisin. Steers were fed the fumonisin treatment diets from day 50 until harvest on day 160; individual animal body weights (BW) were measured on days 0, 50, 100, 150, 159, and 160. Liver, kidney, and skeletal muscle tissue samples were collected at harvest for histopathological analyses, and liver samples were further analyzed for sphinganine (SA) and sphingosine (SO) concentration. Animal performance, carcass data, and liver enzyme concentration were analyzed using a mixed model; categorical data were analyzed via nonparametric models. Contrasts were used to test for linear and quadratic responses. Throughout the study, there was no effect of treatment (P > 0.60), or a linear response (P > 0.16) from increasing fumonisin levels, on BW or dry matter intake (DMI). However, CON tended to have a lower average daily gain (ADG) than the fumonisin treatments during the fumonisin treatment period (P = 0.10), and there was a positive linear response (P = 0.02) of ADG to fumonisin during the treatment period. There were no treatment differences in hot carcass weight, dressing percentage, marbling score, ribeye area, or yield grade. There were no effects of treatment on either liver abscesses (P = 0.95) or telangiectasis (P = 0.13). We observed a treatment difference for SA and SA:SO (P < 0.01), as well as a quadratic response (P < 0.02); both SA and SA:SO increased as dietary fumonisin increased. There were no observed differences between treatments for histopathology scores of kidney (P = 0.16), liver (P = 0.25), or skeletal muscle (P = 0.59) tissue. No adverse effects were observed in steers fed increasing dietary levels of fumonisin for 110 d prior to harvest. While elevated liver amino alcohol concentration did occur, negative effects on growth and carcass characters were not observed. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a model for liver abscesses (LA) in Holstein steers by using an acidotic diet or acidotic diet plus intraruminal inoculation of Fusobacterium necrophorum, Salmonella enterica serotype Lubbock, and Truperella pyogenes. Holstein steers (n = 40; initial BW = 84.9 + 7.1 kg) were individually housed and randomly assigned to either a negative control diet (CON), an acidotic diet (AD), or an acidotic diet plus intraruminal inoculation with the bacterial mixture [ADB; (1 × 109 colony forming unit (CFU)/mL of each bacteria]. Steers in AD and ADB were cycled on (3 d) and off (2 d) a high-starch diet 20 days before intraruminal inoculation of ADB. Following inoculation, AD and ADB remained on the acidotic diet for the remainder of the study. Ruminal pH boluses were randomly inserted into 19 steers across treatments to monitor ruminal pH throughout the study. Steers were euthanized and necropsied to record gross pathology on the lung, rumen, liver, and colon. Culture techniques were used to determine the prevalence inoculated bacteria within LA. Quantitative polymerase chain reaction methods were used to quantify F. necrophorum in rumen tissue. Data were analyzed as a completely randomized design with animal as the experimental unit, where an a of = 0.05 determined significance. Liver abscess prevalence was 43% in ADB vs. 0% in AD and CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD and 78.6% greater than in CON (P ≤ 0.05). There were no pathological differences in the lungs and colons among treatment groups (P ≥ 0.14). There was a treatment × time interaction for ruminal pH, where pH decreased below 5.6 in AD and ADB calves during each cycle of the acidotic diet (P < 0.01). The ADB contained a greater concentration of F. necrophorum subsp. Necrophorum and subsp. Fundliforme within rumen tissue (P = 0.03). Of the LA cultured, 100% contained F. necrophorum, 50% S. enterica, and 0% contained T. pyogenes. The F. necrophorum subsp. Necrophorum was phylogenetically typed and identical to the strain (FN-8LI) infused in the bacterial inoculation. These data suggest that acidotic diet in combination with intraruminal inoculation of the bacterial mixture is sufficient to induce liver abscesses and provides insight on possible mechanisms and origins of LA. Further studies are needed to validate these results and determine if this model may be used to study novel intervention methods. [ABSTRACT FROM AUTHOR]

Most research surrounding liver abscesses involves post-hoc evaluation of naturally occurring abscesses in production settings. Few studies have been designed to experimentally induce abscesses with the purpose of identifying a time course, causality, and associated physiological implications. Therefore, we set out to develop a minimally invasive, reliable, and repeatable model to induce liver abscesses in calves in a controlled research environment to elucidate the genesis and etiology of the disease, with the ultimate goal of developing abscess reduction strategies. Experiment 1 was an attempt to induce abscesses by intraruminal inoculation with Fusobacterium necrophorum, Salmonella lubbock, and Truperella pyogenes (FST) following an intravenous lipopolysaccharide challenge. Holstein steers were harvested 3- and 10-d after inoculation, but no abscesses were detected. Experiments 2 and 3 involved diet manipulation by cycling calves on and off a high-starch, acidotic diet followed by intraruminal inoculation of microbes. In Experiment 2, Holstein calves were fed a negative control diet, an acidotic diet, and an acidotic diet plus bacterial inoculation with FST. No abscesses formed in the control or acidotic diet calves, but 43% of calves fed the acidotic diet with FST inoculation formed liver abscesses, suggesting that acidosis alone is insufficient to produce abscesses. In Experiment 3, treatments consisted of Holstein steers fed a negative control, an acidotic diet, an acidotic diet plus ruminal Fusobacterium necrophorum (F), and an acidotic diet plus Fusobacterium and Salmonella (FS). Again, there were no abscesses in the control or calves fed an acidotic diet alone; however, 40% of calves receiving F presented with an abscess, and 50% of the calves that received FS presented with abscesses. These data suggest that ruminal acidosis in conjunction with a ruminal load of pathogens commonly associated with liver abscesses provides a model that will induce liver abscesses. While the role of barrier dysfunction in the rumen and the lower gastrointestinal tract in formation of abscesses is not fully understood, this work provides a foundation to further explore the etiology of this disease and potential mitigation strategies. [ABSTRACT FROM AUTHOR]

Heifers (n = 1,394; 291 ± 9.9 kg) were used to test the effects of a direct-fed microbial (10-G) on live growth performance and carcass characteristics. Heifers were blocked by arrival day and randomly allocated to treatment (0 or 2g/animal/d; CON and 10-G, respectively) in a randomized complete block design with ten pens per treatment. Heifers were fed for an average of 192 days. Growth and carcass outcomes were analyzed using mixed models with pen as experimental unit and block as random effect. Dry matter intake (P = 0.63), average daily gain (P = 0.69), gain:feed (P = 0.95) and final body weight (P = 0.79) did not differ between treatments. Neither deads and removals (P = 0.52) nor first or second treatment morbidity rates (P = 0.84) were different between treatments. Hot carcass weight (P = 0.19), dressed carcass yield (P = 0.33), 12th rib fat depth (P = 0.73), ribeye area (P = 0.13), calculated empty body fat (P = 0.71) or marbling score (P = 0.20) were not different between treatments. Yield grade distributions did not differ between treatments (P = 0.44), however cattle fed 10-G tended (P = 0.09; 15.78 vs 20.34%) to be represented by fewer USDA Select carcasses. Livers from cattle fed 10-G tended (P = 0.10; 1.02 vs 2.19%) to have a lower frequency of abscesses when compared to CON. Heifers fed 10-G also had fewer (P < 0.05; 5.27 vs 8.51%) severe liver abscesses. These results suggest that supplementing fed beef heifers with 10-G decreased rates of severe liver abscesses without altering live animal performance or carcass characteristics. [ABSTRACT FROM AUTHOR]

Bovine liver abscess outcomes of individual animals (n = 989,296) were observed from 2013 to 2021 on a pen (n = 6,420) basis to quantify liver abscess prevalence and severity, as well as other liver abnormalities such as liver flukes. Cattle originated from 122 feedlots located in Arizona, Colorado, Idaho, Kansas, Minnesota, Missouri, Nebraska, Oklahoma, and Texas. Livers were audited at eighteen different beef abattoirs. Observational categories included sex (heifer, steer), cattle type (Holstein, beef-type), and pen count. Pen counts were grouped (< 40, 41-80, 81-160, 161-320, and >320) to quantify the association of pen size on liver abscess outcomes. Data were analyzed as a series of binomial proportions using generalized linear mixed models with fixed effects of observational categories (cattle type, feedyard location, pen size and sex). Cattle fed in Oklahoma or Texas exhibited greater (P < 0.01) frequency of liver flukes (3.2% vs 0.5%) than cattle fed in Colorado or Nebraska. Cattle fed in Colorado, Kansas, Missouri, Nebraska, Arizona, and Oklahoma exhibited fewer (P < 0.01) total abscesses (23.5%, 26.0%, 23.6%, 19.3%, 16.9%, and 18.1%) than cattle fed in Idaho, Minnesota, and Texas (36.4%, 36.4%, and 33.2%). Beef-type cattle were observed to exhibit fewer (P < 0.01) total abscesses (22.0% vs 41.1%) and fewer (P < 0.01) severe abscesses (10.2% vs 26.4%) than Holstein cattle. Likewise, native heifers exhibited fewer (P < 0.01) total abscesses (20.6% vs 23.3%) and fewer (P < 0.01) severe abscesses (9.3% vs 11.1%) than native steers. Abscess prevalence differed as a function of pen size. Both total abscess and severe abscess rates decreased (P < 0.01) as animal count within a pen increased (32.66%, 27.47%, 27.86%, 23.17%, and 20.33%; 17.20%, 14.48%, 14.80%, 11.45%, and 9.14%). These results suggest liver abscess prevalence and severity is affected by a wide range of factors. [ABSTRACT FROM AUTHOR]

• Consumer perception of antibiotic use in the beef cattle industry has changed overtime. • Alternative management strategies to prevent liver abscesses have been an important research topic for beef cattle. • To reduce prevalence of liver abscesses in finishing beef steers, we must evaluate the possibility of pathogens originating from the hind gut as well as the rumen. • Increased roughage had no impact on ruminal papillary morphology or presence of bacterial species associated with liver abscesses within the ruminal, ileal, or colonic tissues. • Overall, increasing roughage in finishing diets to replace tylosin does not seem applicable for finishing cattle. • The potential for pathogens from the lower gastrointestinal tract to cause liver abscesses warrants further investigation in finishing beef cattle. To reduce prevalence of liver abscesses in finishing beef steers, we must evaluate the possibility of pathogens originating from the hind gut as well as the rumen. We hypothesized that pathogens promoting liver abscess formation are located throughout the gut, and increased dietary roughage levels could improve gut integrity over time. Two hundred sixty-three crossbred beef steers (BW = 258 ± 29 kg) were used in a randomized complete block design with 7-8 hd/pen (8 pens/treatment) using a 2 × 2 factorial treatment structure. Steers received steam-flaked corn-based diets with 5 or 15% corn stalk (CS) inclusion (dry matter basis, DMB) and with (TYL) or without (NTYL) tylosin (7.9 g/T; DMB). Half of the pens in each treatment remained on feed for the entire experiment duration (Exp 1) whereas the remaining half were designated for serial slaughter (Exp 2). Steers were fed each day at 0700 h for an average of 220 d (heavy block = 175 d, light block = 233 d). For Exp 2, eight steers were slaughtered on d 0 to obtain initial tissue samples and thereafter one pen/treatment was slaughtered every 56 d. During serial slaughter, dorsal and ventral sac rumen tissue samples were collected for histopathological evaluation along with ruminal, ileal, and colonic tissues for bacterial isolation. Data were analyzed using mixed models; pen was the experimental unit for performance outcomes and individual animal was the experimental unit for bacterial isolation and histopathological data. No interaction (P ≥ 0.40) between tylosin and CS inclusion was detected for ADG or final BW. Interactions were detected for DMI and G:F; both outcomes were similar when tylosin was included in the diet, however both outcomes differed notably without tylosin. Perimeter and length of ventral rumen papillae decreased (P ≤ 0.01) as DOF increased. In contrast, dorsal rumen papillae perimeter and length increased through d112 and then decreased through d231. Corn stalk inclusion rate did not affect the incidence of bacterial species isolated from the ruminal (P = 0.38), ileal (P > 0.15), or colonic (P > 0.37) epithelial tissues. Cattle consuming the TYL diets tended to have decreased (P = 0.06) presence of ileal Fusobacterium necrophorum subsp. necorphorum and increased (P = 0.07) rates of ruminal Salmonella enterica compared to NTYL. Prolonged consumption of a finishing diet, regardless of CS or TYL inclusion, seemed to be the major source of change in rumen epithelial tissue morphology. [ABSTRACT FROM AUTHOR]