Liver Abscesses In Feedlot Cattle Research Articles

PSXIV-27 Liver Abscesses in Feedlot Cattle: Further Studies on Etiology and Pathogenesis Liver Abscesses in Feedlot Cattle: Further Studies on Etiology and Pathogenesis

Abstract Liver abscesses (LA) are a polymicrobial infection and the causative agents include two subspecies of Fusobacterium necrophorum, necrophorum and funduliforme, and Trueperella pyogenes. Nucleic acid-based 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.

PSXII-29 Development of an in Vitro Rumen Fermentation Model to Assess Fusobacterium Necrophorum Growth Inhibition

Abstract This experiment aimed to determine the impact of growth-inhibitory compounds on F. necrophorum subsp. necrophorum (F.n.n.), a primary etiologic agent of liver abscesses in feedlot cattle, in an in vitro rumen fermentation system. The assessment of inhibition was by quantitative PCR. We hypothesized that the addition of growth inhibitory compounds would reduce F.n.n. concentrations. A 2 x 2 x 6 factorial arrangement of treatments was used. Factors included: 1) sodium lactate (0.0 or 100 mM); 2) bacteria (0 or 1x108 CFU/ml of F.n.n.); and 3) 1 mL of test compound [Control (solvent with no additive); Tylosin: 5 μg/mL; Compound A; Compound B; Compound C; and Compound D]. Prior to morning feeding, rumen contents were collected from a single ruminally canulated steer fed a grain-based finishing diet. Rumen fluid was strained through 4 layers of cheesecloth, mixed with McDougall’s buffer (1:1 ratio; RFB), and 30 mL of the RFB was added into 100 mL-serum bottles containing the appropriate treatments. Serum bottles (n = 3 replicates per treatment) were flushed with CO2 closed with rubber stoppers, crimped with aluminum seals, and incubated at 39ºC for 0, 6, 12, and 24 h. Following each incubation time point, a 2-mL aliquot was removed from each serum bottle under a stream of CO2 to maintain anaerobic conditions. Immediately after sample collection, pH was determined, and DNA was extracted by boiling the sample, centrifugation, and purifying with a GeneClean Turbo DNA extraction kit. The concentration of F.n.n was determined by a quantitative PCR assay targeting the promoter region of the leukotoxin genes. Concentrations of F.n.n. from the RFB were used to adjust F.n.n. concentrations for all treatments at all time points. There was a lactate x test compound x incubation time interaction (P < 0.05) for F.n.n. concentration. In the absence of lactate, serum bottles containing tylosin or test compound treatments had decreased (P < 0.05) F.n.n. concentrations by 24 h post incubation. However, when sodium lactate was added, no treatments had F.n.n. concentrations less than the control treatment at 24 h post incubation (P > 0.05). These data suggest that compounds used in this experiment reduced the concentrations of F.n.n by 24 h post incubation in the absence of additional lactate. However, when lactate, a substrate for F.n.n, was added to the in vitro system, the reduction in F.n.n. growth was not observed.

106 Using a Novel Direct-Fed Microbial as an Alternative for Tylosin Phosphate to Control Liver Abscesses and Decrease Antimicrobial Use in Finishing Beef Steers

Abstract Our objective was to evaluate the use of a novel direct-fed microbial as an alternative to antimicrobials to decrease liver abscesses in feedlot cattle. Angus beef steers (n = 240; initial BW = 263 ± 18.0 kg) were used in a randomized complete block design comprised of 3 BW blocks and 3 pen replications per treatment. Experimental treatments were randomly assigned to pen within BW block and consisted of: 1) negative control, dietary supplement contained no tylosin phosphate (NCON); 2) positive control, dietary supplement contained tylosin phosphate (PCON); 3) positive control with tylosin phosphate removed the last 65 d of the feeding period (PCONW); and 4) novel direct-fed microbial fed at 1 g mixture/animal with 1 × 1011 CFU/g (DFM). By design, initial BW did not differ (P = 0.79) among treatments, and at the end of the 59-d receiving period, there were no differences in final BW (P = 0.25). From d 0 to d 30, ADG, DMI, DMI as a percentage of BW, and G:F did not differ (P ≥ 0.21). Likewise, ADG, DMI, DMI as a percentage of BW, and G:F, from d 31 to d 59, were not different (P ≥ 0.30). From d 0 to d 59, there were no differences in ADG, DMI, DMI as a percentage of BW, nor G:F (P ≥ 0.20). During the finishing period, live- and carcass-adjusted final BW did not differ (P ≥ 0.57) among treatments. During the finishing period, there were also no differences in ADG, DMI, DMI as a percentage of BW, or G:F (P ≥ 0.17). Carcass-adjusted ADG, DMI as a percentage of BW, and G:F also did not differ (P ≥ 0.16). Across treatments, no differences in HCW were noted (P = 0.84). Dressing percentage, marbling score, longissimus dorsi (LM) area, 12th-rib fat thickness, and calculated yield grade (YG) were not different among dietary treatments (P ≥ 0.32). Liver abscess incidence and severity were not affected by dietary treatments (P ≥ 0.13). The inclusion of a novel direct-fed microbial in finishing cattle diets did not affect growth performance, carcass characteristics, nor the prevalence of liver abscesses. However, the removal of tylosin phosphate 65 d before harvest numerically resulted in the lowest frequency of severe liver abscesses when compared with steers not fed tylosin phosphate.

Effect of dry or temper rolling of high- or low-protein wheat and its impact on rumen parameters, growth performance, and liver abscesses in feedlot cattle

This study assessed the impact of dry- (DR) versus temper-rolled (TR) and low- (13%, LP) versus high-protein (18%, HP) wheat on ruminal fermentation, growth, and liver abscesses in feedlot cattle. Crossbred Angus steers (302 ± 34 kg; n = 160; 24 ruminally cannulated) were used in a backgrounding (BG) to finishing (FN) trial. The BG diet consisted of 60% barley silage, 35% wheat, and 5% supplement, and the FN diet contained 10% barley silage, 85% wheat, and 5% supplement (dry matter basis). Four transition (TN) diets were used to adapt cattle to the FN diet. A numerical increase in large particles and reduction in small particles occurred when both HP and LP wheat were TR, with this response being greater for HP wheat. Steers experienced lower ( P ≤ 0.03) ruminal pH with HP-DR and LP-TR than HP-TR wheat during TN. Steers fed HP wheat BG diets tended to exhibit greater ( P ≤ 0.09) gain:feed and NEg than steers fed LP wheat. Greater ( P = 0.01) average daily gains were exhibited by FN steers fed LP wheat. Liver abscesses were more ( P < 0.001) severe with HP wheat. While HP wheat improved the growth of BG cattle, it increased the severity of liver abscesses during FN.

Evaluation of an experimental bio-nutrient feedlot premix on health, growth performance, carcass merit, and prevalence and severity of liver abscesses in feedlot cattle managed under a natural feeding protocol

This research evaluates the efficacy of an experimental diet premix on growth performance, carcass traits, liver abscesses, lung lesions, and health of naturally raised feedlot cattle. A randomized complete block design trial was conducted at a commercial feedlot using 32 pens of steers and heifers (initial BW = 382 kg) and fed an average of 223 d. Antimicrobials, medicated feed additives, or growth-promoting implants were not administered. Treatments included (1) standard diets (CON) and (2) standard diets including a premix (TST) providing lysine and glutamic acid complexes of zinc and manganese, cobalt pectinate, organic iodine (ethylenediamine dihydroiodide), and rumen protected folate. Mortality rate was not affected (P = 0.68) by treatment. Removal for respiratory issues and the natural program fallout rate were greater (P < 0.01) for TST cattle compared with CON. Control cattle had greater DMI, final BW, ADG, and carcass weight (P ≤ 0.05) compared with TST. Control cattle had greater G:F than TST cattle when deads and fallouts were included (P = 0.02), but not when deads and fallouts were excluded (P = 0.92). Percentage carcasses qualifying for each USDA quality grade category did not differ between treatments (P ≥ 0.07). No treatment differences were observed for the percentage of abscessed livers (P = 0.62) or for the percentage of cattle with lung lesions (P = 0.51). The TST diet premix evaluated did not improve growth performance, carcass merit, or feedlot health attributes under the conditions of this study.

333 Development of a 4-Plex Quantitative PCR Assay for the Detection and Quantification of Species and Subspecies of Fusobacterium Necrophorum and Fusobacterium Varium in Bovine Rumen Fluid

Abstract The Fusobacterium genus contains Gram-negative, rod-shaped anaerobic bacteria. Fusobacterium necrophorum and its two subspecies, necrophorum and funduliforme, are normal ruminal inhabitants of cattle. Subsp. necrophorum is the primary causative agent of liver abscesses in feedlot cattle. Fusobacterium varium is also a normal rumen inhabitant, but its role in ruminal fermentation and involvement in liver abscesses is unknown. Currently, no PCR assays exist to quantify F. varium and both subspecies of F. necrophorum. Therefore, our objective was to develop, validate, and determine the applicability of a quantitative PCR assay for quantification of F. varium and the two subspecies of F. necrophorum. Assay targets were the species-specific hgdA gene, encoding for (R)-2-hydroxyglutarylCoA dehydratase subunit alpha, and the subspecies-specific promoter sequence of the leukotoxin gene, lktA. Assay specificity was validated with different species and strains of Fusobacterium, and other bacterial species. Assay sensitivity was determined using pure cultures. Applicability of the assay for quantification of F. necrophorum and F. varium was determined using ruminal fluid from slaughtered cattle. Species and subspecies-level specificity was confirmed. Pure culture quantification limits (CFU/ml) were 2.1x103 for the F. necrophorum species, 5.6x102 for subsp. necrophorum, 1.5x103 for subsp. funduliforme, and 1.8x103 for F. varium. Analysis of ruminal fluid collected from cattle with healthy livers (n=83) and abscessed livers (n=68) indicated that 97% of samples contained F. funduliforme, with mean concentrations of 7.8 x103, and 8.1x103, respectively. Additionally, subsp. necrophorum and F. varium were more prevalent in ruminal fluid from cattle with abscessed livers (41% and 59%) compared with samples from cattle with healthy livers (31% and 41%). In conclusion, subsp. funduliforme appears to be the normal inhabitant of the rumen, while subsp. necrophorum and F. varium are more prevalent in the rumen of cattle with abscessed livers than those with healthy livers.

48 Evaluation of Antimicrobial Activities of Phytophenols Against Bacterial Pathogens That Cause Liver Abscesses in Feedlot Cattle

Abstract Liver abscesses occur in finishing cattle fed high-grain, low-roughage diets. Cattle with abscessed livers do not show any clinical signs and are detected only at slaughter. Liver abscesses, which account for 67% of all liver abnormalities in cattle slaughtered in the United States, are of major economic concern to the beef industry. Fusobacterium necrophorum, Trueperella pyogenes, and Salmonella enterica, particularly the serotype Lubbock, are the main etiologic agents. Currently, the control of liver abscesses is based on in-feed use of antibiotics. The emergence and dissemination of antimicrobial resistance to antibiotics use in animals is a public health concern. Plant-based phenolic compounds, called phytophenols, are known to have antimicrobial properties. Our objectives were to evaluate antimicrobial activities of phytophenols on the liver abscess bacterial pathogens. Phytophenols extracted from rosemary, green tea, grapeseed, organic goji berry, and green coffee were selected for testing. The phytophenols were extracted using 75% aqueous acetone and total phenolic content was determined by a spectrophotometric analysis. Bacteria were cultured in Mueller-Hinton broth (S. Lubbock and T. pyogenes) or anaerobic brain-heart infusion broth (F. necrophorum with and without phytophenols, at 6, 12, 24, and 48 hours and bacterial concentrations were determined. If phytophenol was inhibitory, a micro-broth dilution method was used to quantify the inhibition. Phytophenols from green tea, grape seed, and rosemary inhibited T. pyogenes. Further studies are ongoing to investigate different concentrations of phenolic compounds on the pathogens. Phytophenols that inhibit the pathogens may have the potential to be used as feed additives to prevent liver abscesses.

224 Epimural microbiota and rumen epithelial gene expression in healthy and liver-abscessed animals

Abstract Different dietary and feed additive strategies have been developed to reduce the liver abscess in feedlot cattle, but liver abscesses are still a major problem in beef production. We have limited knowledge about how rumen microbial communities interact with host epithelial gene expression in healthy and liver-abscessed animals. The objective of this study was to investigate the associations between the rumen content associated and rumen epimural microbiome and epithelial gene expression in liver-abscessed and healthy animals. To this end, we collected the ruminal contents and tissue samples from healthy (N=30; score=0, steers n=19 and heifers n=11) and liver-abscessed (N=30; score=A+, steers n=21 and heifers n=9) feedlot cattle at harvest. The bacterial community compositions in the ruminal contents and papillae were evaluated via 16S rDNA sequencing of the V4 region using the Illumina MiSeq platform. Additionally, total RNA was extracted from rumen epithelial tissues and sequenced using the Illumina NextSeq platform. The permutational analysis (PERMANOVA) on Bray Curtis distances matrices showed the microbial community in the ruminal contents was significantly different (P&amp;lt; 0.001) from the bacterial community observed in rumen papillae. The ruminal contents contained a higher abundance of Bacteroidetes and Proteobacteria while papillae contained higher abundance of Firmicutes. The epimural microbiota was different (P&amp;lt; 0.01) between healthy and liver abscessed animals while ruminal contents microbiome was not different between the two groups. The DeSeq2 algorithm identified differentially expressed genes (221) related to MAPK, NF-kappa B signaling pathway, immune and inflammatory response in liver-abscessed animals. Additionally, a wide range of epimural bacterial taxa were correlated (-0.52 to 0.67) with differentially expressed genes. These data demonstrate the interaction between epimural microbiota and the host and its effect on liver abscesses, and indicate the need to study the epimural microbiome for its impact on liver abscesses in feedlot cattle. USDA is an equal opportunity provider and employer.

Investigation of a Reduction in Tylosin on the Prevalence of Liver Abscesses and Antimicrobial Resistance in Enterococci in Feedlot Cattle.

Recent concerns over linkages between antimicrobial resistance in human pathogens and antimicrobial use in livestock have prompted researchers to investigate management strategies that reduce the current reliance on in-feed tylosin to control liver abscesses in feedlot cattle. A total of 7,576 crossbred yearlings were allocated to the study (~253 animals/pen, 10 replicate pens per treatment) and individually randomized to one of three treatments. Tylosin phosphate (11 ppm) was included in-feed (1) for the first 125 days on feed (DOF) (FIRST-78%), (2) for DOF 41 to 161 (LAST-75%), or (3) for the entire feeding period (CON; day 0–161). Fecal composites were collected from the pen floor on days 0, 81, and 160 of the finishing period. Serial dilutions were spread plated for enumeration of enterococci on Bile Esculin Azide (BEA) agar and BEA amended with 8 μg/ml erythromycin. Results indicated that although the proportion of EryR enterococci increased with DOF (P < 0.01), neither treatment (P = 0.34) or treatment × DOF (P = 0.37) affected antimicrobial resistance. Of the 538 isolates, 97% were enterococci, with mixed species isolated early in the feeding period and only Enterococcus hirae isolated at the end. Isolates were most frequently resistant to tylosin (86%), erythromycin (84%), and doxycycline (31%). Macrolide and tetracycline resistant isolates harbored erm(B), msrC, and tet(L), tet(M), tet(O) genes, respectively. Overall, the proportion of EryR enterococci increased (P < 0.05) in all three treatments over the feeding period. Compared to the control cattle, FIRST-78% cattle had more severe (P < 0.05) liver abscesses, while there was a trend (P < 0.08) for this response in LAST-75% cattle. There was no difference (P > 0.05) in total liver abscesses, growth performance, carcass traits, morbidity, or mortality among treatments. These results support the potential to reduce the duration and therefore quantity of tylosin administered to feedlot cattle during the feeding period without impacting animal productivity.

Effect of essential oils on performance, liver abscesses, carcass characteristics and meat quality in feedlot steers

Essential oils (EO) are secondary metabolites derived from plants that have antimicrobial properties which may prevent liver abscesses in feedlot cattle. Seventy-two Angus × Simmental crossbred steers (358 ± 7.6 kg initial BW) were blocked by weight and breed composition and randomly allocated to 3 treatments (4 pens/treatment, 6 steers/pen) to determine the effects of an EO blend or tylosin on performance, liver abscesses, carcass characteristics and meat quality. Treatments were delivered in a premix with dried distillers grains with solubles (DDGS) that were top-dressed daily at a rate of 454 g/steer daily (CON: no additives, TYL: 90 mg/steer daily tylosin, and EO: 1 g/steer daily essential oil blend). The basal diet contained (DM basis) 54% cracked corn, 26% DDGS, 14% corn silage and 6% supplement. Steers were slaughtered at two different time points when a target weight of 624 kg was achieved. Longissimus lumborum muscle samples were taken caudal from the last rib on the right side of each carcass for pH, tenderness, purge and cook loss, and lipid oxidation analyses. Statistical analyses were conducted using the MIXED procedure of SAS. Performance characteristics, including weight, ADG, DMI and gain:feed, did not differ among treatments (P ≥ 0.54). Similarly, no differences were observed in carcass characteristics (P ≥ 0.19). Steers fed EO tended to have an increased prevalence of liver abscesses in the A category (P = 0.10) as compared to CON and TYL. Purge loss was decreased (P = 0.02) for EO steaks compared to CON and TYL, but there were no differences in cook loss, Warner-Bratzler shear force, pH or lipid oxidation among treatments (P ≥ 0.32). In conclusion, an EO blend or tylosin in the diet of finishing steers did not affect growth performance or carcass characteristics, and little difference was observed in liver abscess incidence or meat quality attributes.

Effects of feeding supplemental amino acid complexed zinc for mitigation of liver abscesses in feedlot cattle

Liver abscesses (LA) in feedlot cattle continue to be an issue compromising beef productivity, health and food safety. Ruminal acidosis resulting from the feeding of highgrain finishing diets may compromise ruminal epithelial integrity and predispose cattle to liver abscesses. Dietary zinc (Zn) is known to promote epithelial integrity and may provide an alternative method for reducing LA. Two research projects were conducted to evaluate the effect of dietary Zn supplementation on biomarkers of inflammation and metabolism and LA prevalence and formation in response to a mild acidosis challenge (Study 1). In a second study (Study 2), effects of dietary Zn source and concentration on LA prevalence were evaluated in a longitudinal, retrospective pooled study analysis.

Effect of alpha-tocopherol acetate and ascorbic acid on performance, carcass traits, and incidence and severity of liver abscesses in feedlot cattle.

Liver abscesses (LA) in cattle negatively affect feedlot performance by decreasing ADG, feed intake, and G:F ratio. Abscessed livers are condemned and abdominal adhesions associated with LA can result in extensive carcass trimming during harvest, further compounding adverse economic impact. Given regulatory changes pertaining to the use of in-feed antibiotics in cattle production, there is growing interest in alternatives to antibiotics for LA control. The objective of this study was to evaluate the use of antioxidants, crystalline ascorbate (AOX), and alpha-tocopherol acetate, for mitigation of LA in feedlot cattle. Yearling crossbred heifers (n = 392; initial BW 481 ± 9.4 kg) were blocked by previous treatment and allocated randomly to 24 dirt-surfaced feedlot pens (10 m × 35 m) with 14 heifers/pen. Heifers were weighed, implanted with Component TE-200 implants, and placed into feeding pens. Finishing diets consisted of 60% steam-flaked corn, 30% wet corn gluten feed, 8% alfalfa, and 2% supplement (DM basis) that provided 300 mg/d monensin, and either 200 IU/d alpha-tocopherol acetate (CTL) or 2,000 IU/d alpha-tocopherol acetate plus 500 mg/d crystalline AOX. Heifers were fed once daily ad libitum for 94 d, then weighed and transported 450 km to a commercial abattoir for harvest. Hot carcass weight and incidence/severity of LA were determined the day of harvest, and carcass traits were evaluated following 36 h of refrigeration. Compared to CTL, feeding AOX tended to decrease DMI (10.66 vs. 10.31 kg/d; P = 0.08) and improve G:F (0.1204 vs. 0.1254; P = 0.12), but did not impact ADG, incidence of LA (25.6 vs. 23.5% for CTL and AOX, respectively), HCW (828.4 vs. 830.5 kg for CTL and AOX, respectively), or other carcass traits (P > 0.20). In conclusion, feeding antioxidants are not a viable alternative to decrease incidence of LA in finishing cattle.

Effects of intermittent feeding of tylosin phosphate during the finishing period on feedlot performance, carcass characteristics, antimicrobial resistance, and incidence and severity of liver abscesses in steers.

Liver abscesses (LA) are a source of economic loss for feedlot cattle feedlots, and the 2017 veterinary feed directive has restricted further use of tylosin phosphate to prevention and control of LA. Our objective was to evaluate effects of intermittent tylosin phosphate feeding on incidence and severity of LA in feedlot cattle and presence of total antimicrobial-resistant Enterococcus spp. Steers (n = 312, 411.4 ± 6.71 kg) were blocked by initial BW and randomly assigned to a treatment group. Treatments included a negative control group (no tylosin phosphate throughout the finishing period), a positive control group (tylosin phosphate fed continuously throughout the finishing period), and a group that received tylosin phosphate off-label by feeding the drug on a repeated intermittent basis (1 wk on, 2 wk off). Steers were housed in 24 soil-surfaced pens with 13 steers per pen. Body weights of cattle were obtained every 28 d and at the end of 119 d the steers were weighed and harvested at a commercial abattoir. Fecal samples were collected on days 0, 21, and 118 to characterize antimicrobial-resistant Enterococcus spp. Total LA percentage was greater (P = 0.012) for the no tylosin phosphate treatment compared with the other treatments, but did not differ between the continuous tylosin phosphate treatment and the intermittently fed tylosin phosphate treatment (P = 0.716). No difference was observed among treatments for ADG (P = 0.21), DMI (P = 0.28), or G:F (P = 0.75). Marbling score was lower (P = 0.022) for tylosin phosphate treatment when compared with both intermittent treatment and continuous tylosin phosphate treatment. Enterococcus spp. bacterial counts did not differ by treatment group over time (P > 0.05); however, there was a strong period effect for macrolide resistance among all groups (P < 0.01), suggesting an important environmental component as cattle were first placed in pens and then progressed through the feeding period. We conclude that feeding tylosin phosphate intermittently during the finishing phase decreases the total percentage of LA and maintains feedlot performance and carcass characteristics to the same extent as feeding tylosin phosphate throughout the finishing phase; furthermore, we hypothesize that enteric antimicrobial resistance is a result of longer term antibiotic usage in a particular environment rather than a direct short-term result of the treatment during any given feeding period.

407 Ruminal Epithelial Integrity and Liver Abscesses in Feedlot Cattle.

407 Ruminal Epithelial Integrity and Liver Abscesses in Feedlot Cattle.

Rapid Communication: 16S ribosomal ribonucleic acid characterization of liver abscesses in feedlot cattle from three states in the United States.

Liver abscesses are a major economic burden to beef producers. Although a few causative organisms have been cultured from purulent material, the full polymicrobial diversity of liver abscesses has not been reported. The objective of this study was to characterize purulent material collected from liver abscess in beef cattle produced in different production systems in 3 cattle producing states in the United States using 16S rRNA gene sequencing. Differences between purulent material microbial communities among geographic region of feeding and application of a common antimicrobial were also investigated. Cattle included in the study were fed in California (dairy type) and Colorado and Texas (both beef type). Liver abscesses from a cross section of feedlots, geographic areas, and tylosin phosphate-administered groups were collected at harvest; DNA from 34 liver abscess samples was extracted; and the V4 region of the 16S rRNA gene was amplified and sequenced. Sequences were classified into 5 phyla, 13 classes, and 17 orders in the domain Bacteria. The phyla identified included Bacteroidetes (35.2% of reads), Proteobacteria (28.6%), Fusobacteria (18.2%), Firmicutes (12.4%), and Actinobacteria (5.5%). Sequences matching the genera and , which have previously been identified as causative agents in liver abscesses, were both present in the abscess bacterial communities at a relative abundance of 15.1 and 3.2%, respectively, of the overall relative abundance. Furthermore, 3 of the most common phyla were Gram-negative bacteria. An analysis-of-similarities test was conducted on Euclidean distances to assess differences between cattle treated and not treated with tylosin as well as to assess differences between geographic regions. Geographical region and treatment with tylosin did affect the microbiome ( = 0.002 and = 0.026 respectively); however, a more robust sample scheme is needed to explore these differences. To our knowledge, this is the first publication describing the complex community of liver purulent material using next generation sequencing in cattle. These data provide a framework for research on a more targeted approach to liver abscess prevention and treatment.

The Effect of Tylosin Supplementation and Tylosin Alternatives on Liver Abscess Prevalence, Beef Trim Microbial Populations, and Carcass Characteristics from Feedlot Cattle

ObjectivesTylosin phosphate is a macrolide commonly used for the reduction and prevention of liver abscesses in feedlot cattle. As pressures to reduce antimicrobial use in livestock production rise, pressures to remove Tylosin from cattle feeding strategies continue to increase. This potential removal of Tylosin from cattle feeding could result in significant economic and food safety impacts on the beef industry. In light of this, a blinded, randomized, controlled field trial was conducted to evaluate the effect of Tylosin alternatives on beef trim microbial populations and carcass characteristics from feedlot cattle.Materials and MethodsCommercial steers and heifers (n = 5481 hd) were assigned to ten 4-pen blocks (n = 40 pens) at a commercial feedyard in Texas in the Spring of 2016. At placement, cattle were randomly assigned to 1 of 4 treatment groups including or excluding Tylosin. At the conclusion of the feeding period (Fall 2016), cattle were harvested at a commercial processing facility in Texas. At harvest, but prior to application of interventions, carcass swabs (n = 15/pen) were taken from the plate, and livers abscess scores were recorded at evisceration. Individual carcasses were subjected to USDA yield and quality grading prior to fabrication. At fabrication, approximately 5kg of trim was collected from each pen directly from the trim belt at 3 points on the fabrication floor for a total of approximately 15kg. Trim was retrieved from the chuck, the loin, and the round of carcasses that graded USDA Choice. Trim samples were subjected to detection of generic E.coli and Salmonella enterica following the USDA Microbiology Laboratory Guidebook (MLG) guidelines. In addition, trim and carcass swab samples were analyzed using 16S rRNA gene sequencing to characterize their microbial communities.ResultsCattle supplemented with Tylosin (Tyl) were 1.49 times less likely (P < 0.0001) to develop a liver abscess than cattle not supplemented with Tylosin (NTyl). Hot carcass weights (HCW), dressing percentage, ribeye area, and backfat thickness, did not differ among Tyl and NTyl treatment groups (P > 0.05). However, the percentage of cattle grading USDA Choice was greater for the Tyl group than the percentage grading choice from the NTyl feeding group (P = 0.034). Salmonella enterica was isolated from the trim collected from 10 pens. However, 8 of these 10 trim samples were collected during 1 sampling day (i.e., 2 blocks).ConclusionAlthough previous data and results from the current study highlight the utility of Tylosin inclusion on the reduction of liver abscesses, investigating alternatives is a necessity as pressure to remove antimicrobial compounds from livestock production increases. As alternatives are investigated, understanding their influence on the microbial ecology of trim will not only aid in improving their efficacy, but also assuring the safety of the beef food chain. This understanding will be imperative for the future implementation of strategies aimed to mitigate liver abscesses and maintain the safety and economical production of beef.

Rapid Communication: 16S ribosomal ribonucleic acid characterization of liver abscesses in feedlot cattle from three states in the United States

Rapid Communication: 16S ribosomal ribonucleic acid characterization of liver abscesses in feedlot cattle from three states in the United States

Essential role of methyl donors in animal productivity

Dietary requirements for the methyl donors, choline, betaine and folate, in livestock species are poorly defined and have not been included in diet formulation software or simulation models for animals. A deficiency of methyl donors may promote an inflammatory state, which is significant for the livestock industry because chronic low-grade inflammation is widespread among livestock under commercial conditions. Furthermore, recent evidence showing that methyl donors activate adenosine monophosphate-activated protein kinase, an anti-inflammatory master switch, indicates that dietary methyl-donor supplementation could be used to prevent or ameliorate chronic inflammation and its sequelae in livestock, which include fatty liver disease in dairy cows, fatty liver and kidney syndrome in broilers, fatty liver haemorrhagic syndrome in layers, gut ulcers in pigs, liver abscesses in feedlot cattle, enteritis in poultry and susceptibility to heat stress in all species. Because of the complexity of interactions among methyl donors, a modelling approach inclusive of a supporting research effort will be required to harness the potential of methyl-donor supplementation in livestock production.

Liver abscesses in cattle: A review of incidence in Holsteins and of bacteriology and vaccine approaches to control in feedlot cattle.

Liver abscesses are the primary liver abnormality of feedlot cattle at slaughter. The incidence of liver abscesses is highly variable, but generally ranges from 10% to 20%. The incidence of total and the proportion of severely abscessed livers (A+) are greater in Holsteins fed for beef production and culled dairy cows than in beef breeds. The reason for the greater incidence of liver abscesses in Holstein steers is not known, but one of the reasons is likely because of increased days on feed. The high prevalence in cull cows is likely because no specific intervention, such as use of tylosin in the feed, is approved for use in dairy cows. Liver abscesses are generally a sequela to ruminal acidosis and rumenitis in cattle fed diets high in readily-fermentable carbohydrates and low in roughages; thus, the term "acidosis-rumenitis-liver abscess complex." Liver abscesses are almost always polymicrobial infections with Gram negative anaerobes constituting the predominant flora. Almost all studies have concluded that , a ruminal bacterium, is the primary causative agent and (formerly ) is the secondary pathogen. A limited number of studies have been done on the bacterial flora of liver abscesses of culled dairy cows and Holstein feedlot steers. A recent study has reported on isolation of from liver abscesses of Holstein cattle. The control of liver abscesses in feedlot cattle has depended on the use of antibiotics, particularly tylosin, in the feed combined with sound nutritional management to minimize occurrence of acidosis and subsequent rumenitis. Although there is no evidence of resistance development in , the future of tylosin use as a feed additive in feedlot cattle is uncertain. Regardless, beginning January 2017, the use of tylosin in feedlot cattle for the prevention of liver abscesses will be under veterinary oversight. Although tylosin is widely used in the feedlot industry, there is considerable interest in evaluating antibiotic alternatives, such as essential oils and vaccines, to control liver abscesses. Because liver abscess is a bacterial infection and the pathogenicity and virulence factors of have been studied widely, there have been considerable interest and efforts to develop an efficacious vaccine. The 2 antigens that have been targeted for vaccine production are leukotoxin and outer membrane proteins of .

Clinico-biochemical, ultrasonographic and pathological findings of hepatic abscess in feedlot cattle and buffaloes

Background and aim: Liver abscesses in feedlot cattle have a major economic impact in the beef industry because of liver condemnation and reduced animal performance and carcass yield. The aim of this study was to document the clinicopathological and ultrasonographic findings in cattle and buffaloes with hepatic abscess. Materials and Methods: Three male feedlot cattle and 5 buffaloes suffered from liver abscesses were investigated. Clinical, hemato-biochemical and Ultrasonographic were performed. Liver abscesses were confirmed through centesis and aspiration under ultrasonographic guidance which yield purulent material. Necropsy and histopathological studies were applied on 3 of them, where ultrasonographic diagnosis was confirmed. Results: Altered appetite, loss of body weight, dull demeanor and decreased ruminal motility were recorded in all eight animals. Systemic disturbance and feces abnormalities were appeared with variable degrees. Icterus and abdominal pain were observed only in one cattle. Leucocytosis, hypoalbuminaemia and hyperglobulinaemia were reported in all animals while liver enzymes were mildly elevated only in 3 cattle and one buffalo. Abscess appeared by ultrasonography as hypoechoic to th echogenic circumscribed mass, pinpoint to 10 cm in diameter, with or without echogenic wall, located in the right lobe 7 to th 12 intercostal spaces. Abscesses were located intra-hepatic in 7 (3 cattle and 4 buffaloes) animals and peri-hepatic (between liver and reticulum) in one buffalo.