Bacteriological characterization of bovine liver abscesses has been accomplished by cultural methods but DNA methods are still needed, as many bacteria are not conducive to laboratory culture. In addition to this gap in research, there have been no studies which identify the bacterial presence within healthy, non-abscessed liver tissue. The objective of this study was to compare the bacteriome of both abscessed and non-abscessed bovine livers in an observational case-control study design. Fifty-six livers, obtained from Holstein steers, were scored according to a modified Elanco liver abscess score description where A- was partitioned into active abscesses or scarred where only scars were present. Parenchyma tissue was collected from non-abscessed livers (n=22), and scarred livers (n=7), and purulent material was collected from abscessed livers (n=24), and DNA was extracted for 16s rRNA gene sequence-based bacterial analysis. Across liver samples, 21 total phyla were identified with a mean of 14. Predominant phyla, accounting for > 98% of reads, were Fusobacteria (51.7%), Bacteroidetes (26.9%), Proteobacteria (8.03%), Firmicutes (5.39%), Cyanobacteria (3.85 %) and Actinobacteria (2.21%). Proteobacteria, Cyanobacteria and Firmicutes were greater in non-abscessed and scarred livers, whereas Fusobacteria and Bacteroidetes prevailed in abscessed livers. Non-abscessed livers shared 3,059 operational taxonomic units (OTU) with abscessed livers (total OTU of all livers= 4,167), but non-abscessed livers had greater richness and evenness whereas abscessed livers had greater dominance (P ≤ 0.0014). Liver score affected the relative abundance of OTU (R = 0.463; P = 0.001) but abscessed livers shared ≥ 40% similarity and were not different from each other (P ≥ 0.370). Of the predominant OTU (top 10 as a % of reads), three OTU (Fusobacteria necrophorum, Bacteroides spp., and Trueperella pyogenes) were shared across both abscessed and non-abscessed livers. Fusobacterium necrophorum was the dominant OTU regardless of liver score, and the single most abundant OTU, even among non-abscessed livers. We describe bacterial DNA detected in non-abscessed bovine liver tissue for the first time, which indicates possible presence of viable bacteria with pathogenic potential in apparently healthy liver tissue.
Despite the regular use of feed-grade macrolide-antibiotics, bovine liver abscesses persist, representing a financial burden to pre- and post-mortem sectors of the beef industry. An immunoglobulin-Y (IGY) additive developed to target Fusobacterium necrophorum and Trueperella pyogenes, was evaluated for the control of liver abscesses. Research is needed for the impact of liver abscess severity as well as abscess duration on steer performance and carcass characteristics. Holstein steers (n = 64; initial body weight (BW) = 372.5 ± 2.41 kg) consuming a finishing diet for 188 d were used in a completely randomized design where treatments included: TYL (tylosin phosphate 90 mg/d; n = 32) or IGY (2.5 g/d; n = 32) and steer was the experimental unit. Feed intake was recorded daily while BW and liver ultrasound outcome (normal or abnormal) was recorded every 28 d until slaughter to estimate duration of abscess presence (DUR). Continuous variables of animal growth performance and carcass characteristics were analyzed using the MIXED procedure of SAS. Categorical quality grade and liver data were analyzed using the GLIMMIX procedure of SAS. Treatment did not affect live or carcass-adjusted growth performance (P ≥ 0.131). However, steers fed TYL had greater (P = 0.042) empty body fat (EBF) % and a greater proportion of carcasses grading premium choice than steers fed IGY (P = 0.030). Treatment did not affect prevalence of abscessed livers, abscess severity or estimated abscess duration (P ≥ 0.213) but datasets with greater experimental units are needed to substantiate this outcome. Increasing abscess severity tended (P ≤ 0.10) to linearly reduce carcass-adjusted gain to feed (G:F), fat thickness, and EBF. Carcass dressing % was only affected by severe (A+ and A+AD) abscess scores (P = 0.010). Carcass-adjusted final BW, average daily gain, G:F, and hot carcass weight was decreased only when the estimated DUR was ≥140 d (P ≤ 0.05). Carcass dressing %, however, was linearly affected by estimated liver abscess DUR (P ≤ 0.005), regardless of abscess severity. Preliminary evidence suggests that measuring the duration of liver abscess affliction during the feeding period may also give insight to the degree of performance reduction.
Despite the regular use of macrolide-antibiotics in the diets of feedlot cattle, liver abscesses persist representing a financial burden to both pre- and post-mortem sectors of the beef industry. Alternative strategies, which simultaneously address liver infections and reduce the dissemination of antibiotic-resistant bacteria, are needed. An immunoglobulin-Y (IGY) product, developed to target Fusobacterium necrophorum andTrueperella pyogenes, was evaluated for the control of liver abscesses and its effect on macrolide-resistant Enterococcus growth from feces. Sixty-four Holstein steers (Initial BW= 384±13.5kg) consuming a finishing diet (90% concentrate) for 188 d (Final BW= 660±42 kg) were used in a completely randomized design where treatments included: TYL (Tylosin phosphate fed at 90 mg/hd/day; n = 32) or IGY (fed at 2.5g/hd/day; n = 32). Feed intake was recorded daily and BW was recorded every 28 d until slaughter. After 150 d on treatment fecal samples were randomly obtained from each treatment group four times (n = 40) and cultured on bile-esculine agar enriched with 8 μg/mL of erythromycin. Continuous variables of feedlot growth performance, carcass data and bacterial growth were analyzed using the MIXED procedure of SAS with the fixed effect of treatment and random effects of steer or sampling day, respectively. Ordinal carcass data was analyzed using the FREQ procedure of SAS observing the Cochran-Mantel-Haenszel value. Treatment did not affect DMI (P = 0.21), ADG (P = 0.50) or G:F (P = 0.36). Treatment neither affected hot carcass weight (P = 0.37) nor longissimus muscle area (P = 0.25). However, TYL resulted in greater back fat thickness than IGY (0.32 vs. 0.23 in.; P < 0.02) and consequently greater numerical yield grade (P < 0.02). Quality grade was not affected by treatment (P = 0.65). No treatment difference was observed for liver abscesses prevalence (TYL= 63% vs. IGY= 52%; P = 0.40) or severity (P = 0.23). There was a greater proportion of erythromycin-resistant Enterococcus growth for TYL than IGY (42.6 vs. 21.9%; P < 0.04). Specifically formulated IGY feed additives may be viable alternatives to antibiotics in the diets of feedlot cattle.
Despite the regular use of macrolide-antibiotics in the diets of feedlot cattle, liver abscesses persist representing a financial burden to both pre- and post-mortem sectors of the beef industry. Alternative strategies, which simultaneously address liver infections and reduce the dissemination of antibiotic-resistant bacteria, are needed. An immunoglobulin-Y (IGY) product, developed to target Fusobacterium necrophorum and Trueperella pyogenes, was evaluated for the control of liver abscesses and its effect on macrolide-resistant Enterococcus growth from feces. Sixty-four Holstein steers (Initial BW= 384±13.5kg) consuming a finishing diet (90% concentrate) for 188 days (Final BW= 660±42 kg) were used in a completely randomized design where treatments included: TYL (Tylosin phosphate fed at 90 mg/hd/day; n = 32) or IGY (fed at 2.5g/hd/day; n = 32).Feed intake was recorded daily and BW was recorded every 28 days until slaughter. After 150 d on treatment fecal samples were randomly obtained from each treatment group four times (n = 40) and cultured on bile-esculine agar enriched with 8 μg/mL of erythromycin. Continuous variables of feedlot growth performance, carcass data and bacterial growth were analyzed using the MIXED procedure of SAS with the fixed effect of treatment and random effects of steer or sampling day, respectively. Ordinal carcass data was analyzed using the FREQ procedure of SAS observing the Cochran-Mantel-Haenszel value. Treatment did not affect DMI (P = 0.21), ADG (P = 0.50) or G:F (P = 0.36). Treatment neither affected hot carcass weight (P = 0.37) nor longissimus muscle area (P = 0.25). However, TYL resulted in greater back fat thickness than IGY (0.32 vs. 0.23 in.; P < 0.02) and consequently greater numerical yield grade (P < 0.02). Quality grade was not affected by treatment (P = 0.65). No treatment difference was observed for liver abscesses prevalence (TYL= 63% vs. IGY= 52%; P = 0.40) or severity (P = 0.23). There was a greater proportion of erythromycin-resistant Enterococcus growth for TYL than IGY (42.6 vs. 21.9%; P < 0.04). Specifically formulated IGY feed additives may be viable alternatives to antibiotics in the diets of feedlot cattle.
Heat stress (HS) has been indicated to increase ruminal temperature, increase digestibility, and reduce ruminal pH of steers fed high concentrate diets. However, it is unclear if this effect is the result of greater fermentation rate, slower passage rate or a combination. The effect of ruminal incubation temperature on substrate digestibility and rate of fermentation were evaluated. Four cannulated British-crossbreed steers (BW = 520 kg ± 30 kg) consuming an 87% (DM) concentrate diet were utilized as rumen fluid donors in a randomized complete block design with two incubation treatments (CON=39°C and HS=42°C). Within block, duplicate 125 mL serum bottles containing 200 mg of dietary substrate were inoculated with a 2:1 buffer:ruminal fluid mixture and incubated for 24 h to measure total gas production, fermentation rate, fermentation lag, pH, and ammonia-N concentration. In vitro organic matter digestibility (IVOMD) was measured separately in 100 mL centrifuge tubes. Data were analyzed using the MIXED procedure of SAS using the fixed effect of treatment and random effect of rumen fluid donor (block). There was no treatment effect on total gas production (P = 0.92) or fermentation rate (P = 0.11); however, HS began fermenting substrate sooner than CON (P < 0.005). There was a significant effect of treatment on IVOMD where HS was greater compared to CON (79.3 vs. 70.4%; P = 0.05). Final pH and relative pH change were not different (P ≥ 0.25) likely due to buffering capacity of the in vitro technique Ammonia-N concentration was greater for HS than CON (7.92 vs. 5.33 mM; P < 0.05) and may indicate a temperature effect on ruminal nitrogen availability.In conclusion, it does not appear that incubating at a greater temperature affected the fermentation rate but likely induced a change in fermentation kinetics, which may have contributed to the greater overall IVOMD
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