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

Citation: Amachawadi, R. G., & Nagaraja, T. G. (2016). Liver abscesses in cattle: A review of incidence in Holsteins and of bacteriology and vaccine approaches to control in feedlot cattle. Journal of Animal Science, 94(4), 1620-1632. doi:10.2527/jas2015-0261Liver 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 Fusobacterium necrophorum, a ruminal bacterium, is the primary causative agent and Trueperella (formerly Arcanobacterium) pyogenes 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 Salmonella 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 F. necrophorum, 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 F. necrophorum 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 F. necrophorum

Intermittent Feeding of Tylan Reduces Use of In-Feed Antibiotics While Still Controlling Incidence of Liver Abscesses in Finishing Steers

Liver abscesses are a cause of concern for many feedlots across the country as they lead to a decrease in feedlot performance of finishing cattle as well as a decrease in the final carcass value. Loss in carcass value is due to not only the abscessed liver being condemned, but also due to trim loss associated with the condemned liver. The macrolide drug tylosin phosphate is the drug of choice for metaphylactic treatment of liver abscesses in feedlot cattle. The Food and Drug Administration approved the drug for over-the-counter use, however, from January 2017 all medically important (used in human health) antibiotics that are to be fed in production animal diets will require a veterinary feed directive. The objective of the veterinary feed directive program is to decrease the use of medically important antibiotics in animal production. These veterinary feed directives are similar to a prescription and will encourage the use of the drug in accordance to FDA-guidelines associated with that drug. Macrolide antibiotics are considered medically important and will need a veterinary feed directive. Therefore, it is imperative to look at different methods to control liver abscesses in feedlot cattle. Various studies have noted that macrolide antibiotics (such as tylosin phosphate) are effective against pathogens for moderate to prolonged periods after initial use. The purpose of this study was to determine whether feeding tylosin phosphate periodically throughout the finishing period will have a comparable effect on decreasing liver abscesses as when we would feed tylosin phosphate continuously through the finishing period

Supplemental Zinc Sulfate Interacts with Optaflexx in Feedlot Heifers

Optaflexx is a beta-adrenergic agonist, and is fed to cattle during the final 28 to 42 days on feed to improve growth rate and feed efficiency. Beta-adrenergic agonists are repartitioning agents that stimulate muscle deposition at the expense of fat deposition. Zinc is a trace mineral element that functions as an important component of many enzyme systems, including those associated with nucleic acid synthesis and metabolism of proteins and carbohydrates, thus making it an essential nutrient for growth. The purpose of this study was to evaluate growth, carcass characteristics, and plasma urea nitrogen concentrations in finishing heifers supplemented with Optaflexx at 0 or 200 mg/animal daily, in the presence of 30 or 100 ppm supplemental zinc. We hypothesized that feeding Optaflexx could increase requirements for dietary zinc, and that additional zinc supplementation could increase the growth response to Optaflexx

Determination of Probiotic and/or Chlortetracycline Inclusion Effects on Nursery Pig Growth Performance

A total of 300 nursery pigs (DNA 200 × 400, Columbus, NE; initially 13.0 lb BW) were used in a 42-d study evaluating the effects of feeding chlortetracycline (CTC) in combination with probiotics on nursery pig performance. Probiotics are a class of antimicrobial alternatives designed to enhance growth performance and digestive tract health. Pigs were weaned at approximately 21 d of age and allotted to pens based on initial BW. Pigs were fed a common pelleted starter diet for 4 d and then weighed, and pens were allotted to 1 of 6 dietary treatments based on BW in a completely randomized design. The treatments were arranged in a 2 × 3 factorial with main effects of chlortetracycline (0 vs. CTC at 400 g/ton from d 0 to 42) and probiotic (0 vs. 1 lb/ton Bioplus 2B (Chr. Hansen USA, Inc., Milwaukee, WI)) vs. 1 lb/ton Poultry Star (Biomin America, Inc., San Antonio, TX). Experimental diets were fed in 2 phases (Phase 1: d 0 to 14 and Phase 2: d 14 to 42) and fed in meal form. On d 14 and 28, CTC was removed from the diet according to FDA regulations. For overall performance, there were no interactions (P \u3e 0.05) between added probiotics and CTC. However, pigs fed CTC had improved (P \u3c 0.001) ADG, ADFI, and overall BW compared with those fed diets without CTC. While adding Poultry Star to the diet increased (P \u3c 0.05) BW and ADFI on d 14, there were no consistent benefits of feeding either probiotic alone or in combination with CTC

Effects of Added Copper and Zinc on Growth Performance and Carcass Characteristics of Finishing Pigs Fed Diets with or without Ractopamine HCl

A total of 480 pigs (PIC 327 × 1050; initially 107.4 lb) were used to determine the interactive effects of supplemental Cu, Zn, and Ractopamine HCl on finishing pig growth performance, carcass characteristics, and antimicrobial susceptibility of enteric bacteria. Dietary treatments were arranged in a 2 × 2 × 2 factorial with main effects of added copper sulfate (CuSO4; 0 vs. 125 ppm Cu), added zinc oxide (ZnO; 0 vs. 150 ppm Zn), and Ractopamine HCl (0 vs. 10 ppm during the last 28 d prior to marketing; Paylean®; Elanco Animal Health, Greenfield, IN). All finishing diets were fed in four phases in meal form and contained 11 ppm Cu and 73 ppm Zn from the trace mineral premix. The study design was structured as a randomized complete block design and replicated with two finishing groups. Pigs were randomly allotted to pens upon entry into the finisher barn. Pens of seven (group 1) or eight (group 2) pigs were balanced on initial BW and randomly allotted to 1 of the 4 mineral treatment diets with two treatment replications per weight block and four weight blocks per finishing group. At 28 d prior to marketing, pens within each block and mineral treatment were randomly assigned to receive either 0 or 10 ppm Ractopamine HCl in addition to the mineral treatment. At the conclusion of the 90-d (group 1) or 83-d (group 2) finishing period, carcass characteristics were measured. Adding Cu or Zn alone resulted in numerical improvements in overall F/G and caloric efficiencies; however, the improvements were not additive (Cu × Zn, P = 0.065, 0.068, and 0.064 for F/G and caloric efficiency on a ME and NE basis, respectively). No significant improvements were observed in overall ADG or ADFI due to added Cu and/or Zn. In contrast, Ractopamine HCl improved (P \u3c 0.001) overall ADG, F/G, and caloric efficiency, thereby increasing final BW by 3% with no change in ADFI. Ractopamine HCl also increased (P \u3c 0.001) HCW, percentage carcass yield, and HCW F/G. Adding Zn or Cu alone to diets containing Ractopamine HCl numerically improved percentage carcass yield and HCW F/G, but this effect was not present when the mineral was added to the control diet or when the minerals were fed in combination in the Ractopamine HCl diets (Cu × Zn × Ractopamine, P = 0.011 and 0.024 respectively). Regardless of HCW, pigs fed Ractopamine HCl had decreased (P = 0.014) backfat, increased (P \u3c 0.001) loin depth, and percent fat-free lean. No effects of added minerals on these carcass traits were observed. In summary, the addition of 125 ppm Cu and/or 150 ppm Zn to diets containing Ractopamine HCl failed to improve finishing pig growth performance and carcass characteristics while 10 ppm Ractopamine HCl increased lean tissue deposition and improved feed and caloric efficiency

Feces of Finisher Pigs Have a Low Prevalence of Shiga Toxin-Producing Escherichia coli that are of Public Health Importance

Shiga toxin-producing Escherichia coli (STEC) are major food pathogens that cause mild to bloody diarrhea, including complications of kidney damage and even death, particularly in children and elderly. Seven serogroups of STEC, O26, O45, O103, O111, O121, O145, and O157, called top-7 STEC, are responsible for the majority of STEC infections in the US. Shiga toxins, which are proteins secreted by the bacteria, are major virulence factors contributing to the disease. There are two Shiga toxin types, 1 and 2, encoded stx1 and stx2 gene, respectively and each type has several subtypes. Another major virulence factor, intimin, a protein on the bacterial cell surface encoded by the eae gene, mediates attachment of the bacterial cell to the intestinal epithelial cells. The severity of STEC infections in humans is dependent on the Shiga toxin type and subtype. Cattle are a major reservoir of STEC and carry the bacteria in the hindgut and shed them in the feces, which is a source of contamination of food and water. Swine have also been shown to harbor STEC in the gut and shed in the feces, and a few outbreaks of STEC infections in humans have been linked to pork and pork products. The STEC does not cause infections in cattle, but in swine, particularly in weaned piglets, it causes edema disease. We conducted a study that utilized molecular (polymerase chain reaction [PCR]) and culture methods to determine prevalence and characteristics of top-7 STEC in the feces of finisher pigs collected from ten pig flows in eight states. A total of 598 fecal samples were collected and analyzed. The overall preva­lence of Shiga toxin genes, stx1 or stx2, was 70.1%, and eae was detected in 66.7% of the samples. Based on the PCR method, among the top-7 STEC, O26 (14.4%), O121 (22.9%) and O157 (18.5%) were the predominant serogroups detected. None of the E. coli O157 isolated, a serogroup implicated in pork-linked outbreaks, contained Shiga toxin genes. Although a number of fecal samples were positive for the top-7 STEC serogroups, culture method identified one strain each of stx1-positive O26 (0.2%) and O103 (0.2%), and 23 strains of stx2-positive O121 (3.9%). Serogroups O26 and O103 possessed stx1a subtype and eae, which have the potential to cause serious infections in humans. Serogroup O121 carried the stx2e subtype, which is involved in causing edema disease in swine and rarely implicated in human infections. Our results indicated that finisher pig feces contain a high prevalence of top-7 E. coli serogroups, but prevalence of top-7 serogroups that have the ability to produce Shiga toxins was low. In conclusion, a majority of STEC shed in the feces of swine are not of major public health importance

Impact of Added Copper and Chlortetracycline on Growth Performance of Nursery Pigs

A total of 320 nursery pigs (DNA 200 × 400 barrows; initially 16.3 lb BW) were used in a 28-d trial to determine the effect of copper (Cu) and chlortetracycline (CTC), fed alone or in combination, on growth performance of weanling pigs. Pigs were weaned at approximately 21 d of age and fed a common pelleted starter diet (non-medicated) for 7 d after weaning. Pigs were allotted to dietary treatments based on BW and location in a randomized complete block design. Dietary treatments were arranged as a 2 × 2 factorial with main effects of added Cu (0 vs. 200 ppm Cu from copper sulfate) and CTC (0 vs. 440 ppm CTC). Experimental diets were corn-soybean meal-based and were fed in one phase for 28 d in meal form. There were 5 pigs per pen and 8 replications per treatment with each replication consisting of a pair of adjoining pens. The results showed no evidence for an interactive effect of Cu and CTC for any of the performance and economic variables (P \u3e 0.05). From d 0 to 14, added Cu increased (P \u3c 0.05) ADG and ADFI and added CTC improved (P \u3c 0.05) ADG, ADFI, and F/G. From d 14 to 28, the addition of CTC to the diet improved (P \u3c 0.05) ADG and ADFI, but there was no evidence for a Cu effect. For the overall experimental period (d 0 to 28), pigs fed diets with CTC had improved (P \u3c 0.05) ADG, ADFI, and F/G, but there was no evidence for a Cu effect. The inclusion of either Cu or CTC increased (P \u3c 0.05) BW on d 14 and 28. Regarding the economics, added dietary Cu increased (P \u3c 0.05) feed cost per pig and value of gain per pig, but not income over feed cost (IOFC). The addition of CTC to the diet increased (P \u3c 0.05) feed cost per pig, value of gain per pig, and IOFC. In conclusion, the findings of the present study characterize a beneficial effect of feeding Cu for 14 d on growth performance of young pigs (16 to 25 lb) and a positive effect of including CTC in nursery diets. The lack of interactive effects between Cu and CTC suggests that the responses of Cu and CTC on growth performance of nursery pigs are as efficacious when fed alone or in combination

Determining the Minimum Inhibitory Concentration of Medium Chain Fatty Acids for Generic Escherichia coli, Enterotoxigenic Escherichia coli, Salmonella Typhimurium, and Campylobacter coli

Research has demonstrated that medium chain fatty acids (MCFA) can serve as reduction strategies for bacterial and viral pathogens in animal feed and ingredients. However, it is unknown how the type or level of MCFA impact bacteria growth. This can be tested through a minimum inhibitory concentration (MIC) benchtop assay, which identifies the lowest concentration of a chemical that prevents visible growth of a bacterium. The objective of this study was to 1) determine the MCFA MIC of C6:0, C8:0, C10:0, and C12:0 for generic Escherichia coli, Enterotoxigenic Escherichia coli, Salmonella Typhimurium, Campylobacter coli, and Clostridium perfringens; 2) determine the MIC of commercial based MCFA products against the same bacteria; and 3) determine the effect of 2 commercial based MCFA products on the quantification of Enterotoxigenic Escherichia coli. For Exp. 1 and 2, MIC were determined by modified microbroth dilution method using a 96 well microtiter plate with a concentration of 105 CFU/mL for each bacterial strain. For Exp. 3, the two products selected for quantification were mixed with a complete swine diet and inoculated with two concentrations (106 or 102 CFU/g of feed) of a NalR strain of Enterotoxigenic Escherichia coli (ETEC) for bacterial enumeration. From Exp. 1, the MIC of MCFA varied among bacteria species. The lowest MIC of the MCFA was 0.43% of a 1:1:1 blend of C6:0, C8:0, and C10:0 for Campylobacter coli, 0.25% C12:0 for Clostridium perfringens, 0.60% 1:1:1 blend for generic Escherichia coli, 0.53% C6:0 for ETEC, and 0.40% C6:0 for Salmonella Typhimurium. In Exp. 2, products containing high concentrations of C6:0 or C8:0 had lower MIC in gram negative bacteria. In Exp. 3, feed containing either of the commercial based MCFA products reduced (linear, P \u3c 0.05) quantifiable ETEC. Overall, the inhibitory efficacy of MCFA varies among bacteria species. This suggests that MCFA mixtures may provide a wider spectrum of bacterial control. As commercial products containing MCFA become available for livestock, it is important to consider the interaction between MCFA chain length and concentration on the potential to effectively mitigate various feed-based bacteria

Evaluating the Route of Antibiotic Administration and its Effect on Nursery Pig Growth Performance

This experiment was conducted to determine the influence of the route of antibiotic administration (in-feed vs. in-water) on nursery pig growth performance. A total of 2,592 pigs (L337 × 1050, PIC Hendersonville, TN; initially 14.5 lb) were used in a 28-d trial. Pigs were weaned at 21 d of age and placed in a commercial research facility with 27 pigs per pen. After a 7-d pre-trial period, pens of pigs were assigned to weight blocks in a randomized complete block design. There were 12 replications per treat­ment with pen as experimental unit for in-feed medication treatments and a pair of pens as the experimental unit for water medication treatments. The six treatments included a control (no medication), chlortetracycline (CTC) provided via feed or water to achieve 9.98 mg/lb body weight (BW), tiamulin in feed (2.27 mg/lb BW) or water (10.43 mg/lb BW), or a combination of CTC and tiamulin in feed. Experimental treat­ments were provided for 14-d followed by a 14-d period without medication. For statis­tical analysis, the interaction of antibiotic type × route of administration was tested in a 2 × 2 factorial with main effect of antibiotic type (CTC or tiamulin) and route of administration (in-feed or in-water). Pairwise comparisons were also made between the control and all individual treatments. From d 0 to 14 (P \u3c 0.05), d 14 to 28 (P \u3c 0.10), and d 0 to 28 (P \u3c 0.05) there was an antibiotic × route of administration interac­tion observed for average daily gain (ADG). The interactions were a result of pigs fed diets containing CTC having improved (P \u3c 0.05) ADG compared to CTC in-water, whereas pigs provided tiamulin in-water exhibited improved ADG compared with tiamulin in feed. There was an antibiotic × route of administration interaction observed for feed-to-gain ratio (F/G) from d 0 to 14 and 0 to 28. Pigs provided tiamulin in the feed had the poorest F/G, whereas F/G was not different among the other treatments. Providing CTC in the feed or water or tiamulin in the water improved (P \u3c 0.05) ADG compared to pigs fed the control diet. Providing either CTC or tiamulin in the feed increased (P \u3c 0.05) average daily feed intake (ADFI) as compared with providing the antibiotics in water. Pigs fed antibiotics in the feed had increased (P \u3c 0.05) ADFI compared to the control with those provided antibiotics in the water being margin­ally greater (P \u3c 0.10) in ADFI than the control. For ADG (d 0 to 28), pigs provided CTC in feed, tiamulin in the water, or the combination of CTC and tiamulin in the feed during the treatment period had increased ADG (P \u3c 0.05) compared to pigs fed the control diet. For ADFI, there was no evidence of an interaction or main effects; however, when compared to the control, pigs provided CTC in-feed, tiamulin in-water, or the combination in the feed all had increased ADFI. In summary, providing CTC in feed with or without tiamulin or tiamulin in the water improved nursery pig growth performance

Effects of Tylosin Administration Routes on the Development of Antimicrobial Resistance in Fecal Enterococci of Finishing Swine

Antibiotics can be administered via various routes in pigs, which may influence antimicrobial resistance development. A total of 40 barrows and 40 gilts (Line 600 × 241; DNA, Columbus, NE; initially 207 ± 7.9 lb) were used in a 35-d trial to determine the effects of tylosin administration route on pig growth performance and development of antimicrobial resistance in fecal Enterococcus spp. isolates. Pens of pigs (1 pig/ pen, 20 pigs/treatment) were blocked by initial body weight (BW) and gender. Within blocks, pens were randomly allotted to 1 of 4 treatments. The antibiotic treatments followed US label directions and were: 1) no antibiotic (Control); 2) 110 mg tylosin per kg of feed for 21 d (Feed); 3) 8.82 mg tylosin per kg of BW through intramuscular injection twice daily for the first 3 d of each wk during the 3-wk treatment period (Injection); and 4) 66 mg of tylosin per liter of drinking water for the first 3 d of each wk during treatment period (Water). Treatments were offered during d 0 to 21, after which all pigs were fed a common diet with no antibiotic until d 35. Fecal samples were collected on d 0, 21, and 35. No evidence for route × gender interactions (P \u3e 0.55) were observed for any growth responses. From d 0 to 21, control pigs and pigs fed medicated feed had greater (P \u3c 0.05) average daily gain (ADG) than those that received injected tylosin, with the ADG of pigs receiving tylosin through the water intermediate. There was no evidence for different average daily feed intake (ADFI) among treatment groups. Pigs that received tylosin through injection or water had poorer (P \u3c 0.05) feed efficiency (F/G) compared with control pigs, but there was no evidence for difference from pigs receiving tylosin through feed. Among the medicated pigs, total tylosin dose administered was the greatest through injection, second highest through feed, with the water medication route the lowest. No evidence for route × day interactions (P \u3e 0.23) were observed for the development of bacterial resistance to any antibiotics. Enterococcal isolates collected from pigs receiving tylosin via feed or injection were more resistant (P \u3c 0.05) to erythromycin and tylosin compared with control pigs and those that received tylosin through water. The estimated probability of antimicrobial resistance to these 2 antibiotics was greater on d 21 and 35 than d 0. In summary, tylosin injection resulted in poorer ADG and F/G of finishing pigs, likely due to stress associated with handling and injection. Tylosin administration through injection and feed resulted in greater probability of enterococcal resistance to erythromycin and tylosin compared with in-water treatment, which is likely a combined effect of administration route and dosage