Evaluation of Feeding Dried Distiller's Grains with Solubles and Dry-Rolled Corn on the Fecal Prevalence ofEscherichia coliO157:H7 andSalmonellaspp. in Cattle

Corn-Based Distillers' Grains in Diets for Feedlot Cattle Are Associated with the Burden of Escherichia coli O157 in Feces

Inclusion of distillers' grains (DGs) has been associated with increased prevalence of Escherichia coli O157:H7 in cattle housed in research settings. Our objective was to quantify the relationship between inclusion of DGs in commercial feedlot rations and the burden of E. coli O157. A convenience sample of 10 feedlots was enrolled based on DG use in finishing diets; 1 cohort included 5 feedlots in which DGs were greater than 15% of the dietary dry matter and the other cohort consisted of 5 feedlots at a concentration less than 8%. Sampling occurred at each feedlot on four occasions at ∼6-week intervals. At each feedlot visit, 4 pens of cattle within 3 weeks of slaughter were selected and 24 freshly voided fecal pats were sampled. Ten-gram samples were enriched in 90 mL of modified tryptic soy broth with novobiocin (20 mg/L) for 14 h at 42°C. Enrichments were subjected to immunomagnetic separation, plating onto chromogenic agar with novobiocin (5 mg/L) and potassium tellurite (2.5 mg/L), incubation for 18 h at 37°C, and latex agglutination of morphologically typical colonies. E. coli O157 was recovered from 16.7% of 3840 samples. Adjusted prevalence was 14.3% after controlling for within-feedlot and within-pen clustering. Prevalence during each sampling period was 19.9% (round 1), 21.0% (round 2), 14.1% (round 3), and 11.7% (round 4). Prevalence varied between cohorts, but this difference varied over time (p = 0.06). Among those with greater than 15% of the diet as DGs, prevalence was greater than those with less than 8% inclusion for all rounds of sampling (p < 0.01). Averaged across time, prevalence was 23.9% and 9.4% for those with greater than 15% and those with less than 8% of DGs, respectively. While observational, these data provide real-world support of reports of increased E. coli O157:H7 burden associated with DG use in cattle diets.

A randomized controlled trial to evaluate the effects of dietary fibre from distillers grains on enterohemorrhagic Escherichia coli detection from the rectoanal mucosa and hides of feedlot steers

Feeding high levels (≥40% dry matter) of distillers grains may increase the risk for cattle to carry enterohemorrhagic Escherichia coli (EHEC) O157. The mechanism for the increased risk is not known nor whether non-O157 EHEC are similarly affected. Our objective was to test whether the fibre content or other components of modified distillers grains plus solubles (MDGS) affects the probability for cattle to carry EHEC serogroups of public health importance. A 2 × 2 plus 1 factorial treatment arrangement within a randomized block design was utilized. Within each of four blocks, 25 feedlot pens (n = 8 steers/pen) were assigned randomly to (i) corn-based control diet; (ii) 20% dry matter (DM) MDGS; (iii) 40% DM MDGS; (iv) corn bran added to corn-based diet to match fibre of 20% MDGS or (v) 40% MDGS. Rectoanal mucosa swabs (RAMS) were collected on day (d)0, d35, d70 and d105; hide swabs were collected on the last feeding day. Samples were tested for EHEC by a molecular screening assay. The effects of fibre source and fibre level on EHEC carriage were tested using multilevel logistic regression (generalized linear mixed models; α = 0.05). EHEC O45 RAMS detection was associated with fibre level, source and sampling day. EHEC O103 RAMS detection increased by feeding 40% MDGS but not the corresponding corn bran diet. Hide contamination by EHEC O45 or O103 was less likely in cattle fed MDGS compared to corn bran diets. EHEC O111 RAMS detection decreased by feeding 40% MDGS but not by feeding the corresponding corn bran diet. Detection of EHEC O157 or O145 was not associated with dietary factors. Feeding 40% MDGS increased the probability for carriage of some EHEC serogroups but decreased probability of others, which indicated that EHEC serogroups have different risk factors associated with feeding MDGS and little association with dietary fibre.

Rapid systematic review and meta-analysis of the evidence for effectiveness of primary production interventions to control Salmonella in beef and pork

Non-typhoidal Salmonella spp. (hereafter referred to as Salmonella) on beef and pork is an important cause of foodborne illness and death globally. A systematic review of the effectiveness of interventions to reduce Salmonella prevalence or concentration in beef and pork was undertaken. A broad search was conducted in Scopus and CAB abstracts. Each citation was appraised using screening tools tested a priori. Level 1 relevance screening excluded irrelevant citations; level 2 confirmed relevance and categorized studies. Data were then extracted, and intervention categories were descriptively summarized. Meta-analysis was performed to provide a summary estimate of treatment effect where two or more studies investigated the same intervention in comparable populations. The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) approach was used to assess the confidence in the estimated measures of intervention effect for data subgroups.

The Role of Biofuels Coproducts in Feeding the World Sustainably

One of the grand challenges facing our society today is finding solutions for feeding the world sustainably. The food-versus-fuel debate is a controversy embedded in this challenge, involving the trade-offs of using grains and oilseeds for biofuels production versus animal feed and human food. However, only 6% of total global grain produced is used to produce ethanol. Furthermore, biofuels coproducts contribute to sustainability of food production because only 1% to 2.5% of the overall energy efficiency is lost from converting crops into biofuels and animal feed, and approximately one-third of the corn used to produce ethanol is recovered as feed coproducts. Extensive research has been conducted over the past 15 years on biofuels coproducts to (a) optimize their use for improving caloric and nutritional efficiency in animal feeds, (b) identify benefits and limitations of use in various animal diets,

Evaluation of Selected Nutrients and Contaminants in Distillers Grains from Ethanol Production in Texas

This article contains the results of the evaluation of distillers grain (DG) coproducts from different ethanol plants around the United States and supplemented in animal diets in Texas, based on samples analyzed from 2008 to 2014. The samples were assessed for concentration, occurrence, and prevalence of selected nutrients and contaminants. Protein and sulfur contents of DG were largely different between maize and sorghum coproducts, as well as wet distillers grain with solubles (WDGS) and dried distillers grain with solubles (DDGS), indicating a significant effect of grain feedstock and dry grind process stream on DG composition and quality. Salmonella was isolated in 4 DDGS samples of a total of 157 DG samples, a percentage (2.5%) that is lower than the percentage of Salmonella -positive samples found in other feed samples analyzed during the same period. A small amount of virginiamycin residue was found in 24 maize DDGS, 1 maize WDGS, and 2 sorghum DDGS samples of 242 samples in total. One sorghum DDGS sample of 168 DG samples was contaminated with animal protein prohibited for use in ruminant feed and was channeled to poultry feed. The concentrations of aflatoxin and fumonisin DG coproducts averaged 3.4 μg/kg and 0.7 mg/kg, respectively. Among contaminated maize DG samples, five DDGS samples for aflatoxin contained a higher concentration than the U.S. Food and Drug Administration (FDA) minimum action level of 20 μg/kg for use in animal feed, whereas no sample for fumonisin was found above the action level of 5 mg/kg. The study provides the most current results involving DG coproducts and associated hazards that will assist development of food safety plans required by the FDA in their September 2015 rule titled "Current Good Manufacturing Practice Hazard Analysis and Risk Based Preventive Controls for Food for Animals."

Effect of Feeding Bacillus subtilis natto on Hindgut Fermentation and Microbiota of Holstein Dairy Cows

The effect of Bacillus subtilis natto on hindgut fermentation and microbiota of early lactation Holstein dairy cows was investigated in this study. Thirty-six Holstein dairy cows in early lactation were randomly allocated to three groups: no B. subtilis natto as the control group, B. subtilis natto with 0.5×10(11) cfu as DMF1 group and B. subtilis natto with 1.0×10(11) cfu as DMF2 group. After 14 days of adaptation period, the formal experiment was started and lasted for 63 days. Fecal samples were collected directly from the rectum of each animal on the morning at the end of eighth week and placed into sterile plastic bags. The pH, NH3-N and VFA concentration were determined and fecal bacteria DNA was extracted and analyzed by DGGE. The results showed that the addition of B. subtilus natto at either treatment level resulted in a decrease in fecal NH3-N concentration but had no effect on fecal pH and VFA. The DGGE profile revealed that B. subtilis natto affected the population of fecal bacteria. The diversity index of Shannon-Wiener in DFM1 decreased significantly compared to the control. Fecal Alistipes sp., Clostridium sp., Roseospira sp., beta proteobacterium were decreased and Bifidobacterium was increased after supplementing with B. subtilis natto. This study demonstrated that B. subtilis natto had a tendency to change fecal microbiota balance.

Capacity of the bovine intestinal mucus and its components to support growth of Escherichia coli O157:H7

Colonization of the gastrointestinal tract of cattle by Shiga toxin-producing Escherichia coli increases the risk of contamination of food products at slaughter. Our study aimed to shed more light on the mechanisms used by E. coli O157:H7 to thrive and compete with other bacteria in the gastrointestinal tract of cattle. We evaluated, in vitro, bovine intestinal mucus and its constituents in terms of their capacity to support growth of E. coli O157:H7 in presence or absence of fecal inoculum, with and without various enzymes. Growth of E. coli O157:H7 and total anaerobic bacteria were proportionate to the amount of mucus added as substrate. Growth of E. coli O157:H7 was similar for small and large intestinal mucus as substrate, and was partially inhibited with addition of fecal inoculum to cultures, presumably due to competition from other organisms. Whole mucus stimulated growth to the greatest degree compared with other compounds evaluated, but the pathogen was capable of utilizing all substrates to some extent. Addition of enzymes to cultures failed to impact growth of E. coli O157:H7 except for neuraminidase, which resulted in greater growth of E. coli O157 when combined with sialic acid as substrate. In conclusion, E. coli O157 has capacity to utilize small or large intestinal mucus, and growth is greatest with whole mucus compared with individual mucus components. There are two possible explanations for these findings (i) multiple substrates are needed to optimize growth, or alternatively, (ii) a component of mucus not evaluated in this experiment is a key ingredient for optimal growth of E. coli O157:H7.

Cattle Production Systems: Ecology of Existing and Emerging Escherichia coli Types Related to Foodborne Illness

Shiga toxin–producing Escherichia coli (STEC), particularly STEC O157, cause rare but potentially serious human infections. Infection with STEC occurs by fecal-oral transmission, most commonly through food. Cattle are the most important reservoir for human STEC exposure, and efforts to control the flow of STEC through beef processing have reduced rates of human illness. However, further reduction in human incidence of STEC may require control of the pathogen in cattle populations. The ecology of STEC in cattle production systems is complex and explained by factors that favor (a) colonization in the gut, (b) survival in the environment, and (c) ingestion by another cattle host. Although nature creates seasonal environmental conditions that do not favor STEC transmission in cattle, human efforts to control STEC by environmental manipulation have not succeeded. Vaccines and direct-fed microbial products have reduced the carriage of STEC by cattle, and other interventions are under investigation.

Interventions for preventing diarrhea-associated hemolytic uremic syndrome: systematic review

BACKGROUND

Hemolytic Uremic Syndrome (HUS) may follow infection with Shiga-toxin-producing organisms, principally E. coli O157: H7 (STEC), causing high morbidity and mortality. Our aim was to identify interventions to prevent diarrhea-associated HUS.

METHODS

Systematic search of the literature for relevant systematic reviews (SRs), randomised controlled trials (RCTs) and public health guidelines.

RESULTS

Of 1097 animal and 762 human studies, 18 animal studies (2 SRs, 2 reviews, plus 14 RCTs) and 6 human studies (3 SRs, plus 3 RCTs) met inclusion criteria. E. coli O157: H7 Type III secreted protein vaccination decreased fecal E. coli O157 shedding in cattle (P = 0.002). E. coli O157: H7 siderophore receptor and porin proteins (SRP) vaccines reduced fecal shedding in cows (OR 0.42 (95% CI 0.25 to 0.73) and increased anti-E. coli 0157: H7 SRP antibodies in their calves (P < 0.001). Bacterin vaccines had no effect. Probiotic or sodium chlorate additives in feeds reduced fecal E. coli O157 load as did improved farm hygiene (P < 0.05). Solarization of soil reduced E. coli O157: H7 contamination in the soil (P < 0.05). In an RCT examining the role of antibiotic treatment of E. coli O157: H7 diarrhea, HUS rates were similar in children treated with Trimethoprim-sulfamethoxazole and controls (RR 0.57; 95% CI 0.11 to 2.81). In another RCT, HUS rates were similar in children receiving Synsorb-Pk and placebo (RR 0.93; 95% CI 0.39 to 2.22). In one SR, hand washing reduced diarrhea by 39% in institutions (IRR 0.61; 95% CI 0.40 to 0.92) and 32% in community settings (IRR 0.68; 95% CI 0.52 to 0.90) compared to controls. Guidelines contained recommendations to prevent STEC transmission from animals and environments to humans, including appropriate food preparation, personal hygiene, community education, and control of environmental contamination, food and water quality.

CONCLUSIONS

Animal carriage of STEC is decreased by vaccination and improved farm practices. Treatment of STEC diarrhea with antibiotics and toxin-binders did not prevent HUS. Public health interventions are the key to preventing STEC-associated diarrhea and HUS.

In vitro studies on the effect of pH and volatile fatty acid concentration, as influenced by diet, on the survival of inoculated nonacid- and acid-adapted Salmonella in bovine rumen fluid and feces

The aim of this study was to examine the effect of pH and volatile fatty acids concentrations, as influenced by bovine diet, on the survival of Salmonella in inoculated rumen fluid and feces, thus providing preliminary data on the potential application of dietary manipulation as a preharvest control strategy to reduce Salmonella contamination at slaughter. The in vitro survival of nonacid- and acid-adapted (AA) Salmonella cocktails (Salmonella serovars: Dublin, Enteritidis, Newport, Typhimurium, and Typhimurium DT104) in rumen fluid and feces, collected from fistulated cattle fed five different diets ([1] grass, [2] grass + concentrate, [3] grass silage, [4] hay, and [5] a high grain diet), was examined at 6°C and 15°C (feces) and at 37°C (rumen fluid). The pH of the rumen fluid ranged from 5.77 to 6.61 and the feces from 6.86 to 7.06. Salmonella D-values in rumen fluid were statistically similar, regardless of dietary source. Although prolonged survival (up to 84 days) was observed in feces, diet did affect survival with significantly (p < 0.05) higher D-values obtained in feces from diets 3 and 4 (AA cells at 6°C) and significantly (p < 0.05) lower D-values for diet 5 (AA cells at 15°C). It was concluded that changes in rumen pH and volatile fatty acids profile and concentrations, based on dietary manipulation, may not reduce the persistence and dissemination of Salmonella in cattle.

Inclusion of dried or wet distillers' grains at different levels in diets of feedlot cattle affects fecal shedding of Escherichia coli O157:H7

Our objectives were to evaluate the prevalence of Escherichia coli O157:H7 in cattle fed diets supplemented with 20 or 40% dried distillers' grains (DG) (DDG) or wet DG (WDG) and assess whether removing DG from diets before slaughter affected fecal shedding of E. coli O157:H7. Eight hundred forty steers were allocated to 70 pens (12 steers/pen). Treatments were no DG (control), 20% DDG or WDG, and 40% DDG or WDG, and each was replicated in 14 pens. In phase 1, eight floor fecal samples were collected from each pen every 2 weeks for 12 weeks for isolation of E. coli O157:H7 and detection of high shedders. In phase 2, half of the pens with DG were transitioned to the no-DG control diet, and pen floor fecal samples were collected weekly from all pens for 4 weeks. During phase 1, prevalence of E. coli O157:H7 was 20.8% and 3.2% for high shedders. The form of DG had no significant effect on fecal E. coli O157:H7 shedding. The prevalence levels of E. coli O157:H7 and the numbers of high shedders were not different between diets with 0 or 20% DG; however, cattle fed 40% DG had a higher prevalence and more high shedders than cattle fed 0 or 20% DG (P ≤ 0.05). During phase 2, overall and high-shedder prevalence estimates were 3.3% and <0.1%, respectively, and there were no differences between those for different DG forms and inclusion levels or when DG was removed from diets. The form of DG had no impact on E. coli O157:H7; however, fecal shedding was associated with the DG inclusion level.

The effect of bovine diet on Salmonella survival in synthetic abomasal fluid

AIMS

To investigate the effect of diet on the survival of Salmonella in the bovine abomasum.

METHODS AND RESULTS

Five fistulated cows were randomly assigned to one of five diets denoted as: (i) 100% grass, (ii) grass + 5·3 kg DM concentrate, (iii) 100% grass silage, (iv) 100% hay and (v) maize/grass silage plus concentrates. Rumen fluid was harvested from each dietary treatment and inoculated with nonacid (NA) and acid-adapted (AA) 5-strain Salmonella cocktails. After 24-h incubation period, Salmonella were acid challenged to synthetic abomasum fluid (SAF, pH 2·5) for 5 h to determine their resistance to low pH. The study found that the volatile fatty acids composition and the pH profile of bovine rumen fluid were significantly altered (P <0·05) by some of the dietary treatments but not others. Regression analysis found that significantly higher numbers of acid-adapted Salmonella survived in SAF after incubation in rumen fluid from diets 1, 2 and 4, but fewer significant differences were found between diets for nonacid-adapted Salmonella. The results suggest that the acid-adapted cells were subjected to a higher level of cell injury than the nonadapted cells.

CONCLUSIONS

 Pre-incubation in rumen fluid did influence the resistance of nonacid and acid-adapted Salmonella to SAF but it was dependant on the dietary treatment fed to the cows.

SIGNIFICANCE AND IMPACT OF THE STUDY

 This study examined the use of diet, as a modulating factor to limit the bovine excretion of Salmonella with a view to providing a scientific basis for the design of dietary management controls in the future.

Enumeration and strain characterization of fecal Escherichia coli associated with feeding triticale dried distillers grain with solubles in beef cattle diets

Triticale dried distillers grain with solubles (TDDGS), a major by-product of the bioethanol industry, has potential for utilization in animal feed. This study investigated the changes in generic fecal Escherichia coli strains associated with inclusion of TDDGS in cattle diets. Within this study, a longitudinal experiment (112 days) examined the effect of step-up increasing TDDGS inclusion from control to a final diet containing 30% TDDGS among cattle (n = 4), and a short-term experiment (28 days) compared animals (n = 16) fed control, 20%, 25%, or 30% TDDGS diets. We found that incorporation of either 20%, 25%, or 30% TDDGS did not have any effect on the amount of total E. coli shedding over either the longitudinal (p = 0.06) or the short-term (p = 0. 87) study. In both the experiments, 67% of the total E. coli isolates were found to be resistant to one or more of the 17 antimicrobials tested. Among the resistant isolates, cephalothin was the most prevalent resistance (44% isolates). Over the duration of the study, tet(C) was a commonly detected resistance gene in tetracycline-resistant E. coli. Significant diversity was observed among isolates with 33 and 31 pulsed-field gel electrophoresis patterns clustering into 11 and 10 restriction endonuclease digestion pattern clusters for the longitudinal and short-term studies, respectively. Neither the duration of feeding nor increasing the proportion of TDDGS within the diet affected the diversity of E. coli resistance phenotypes or the clonal relatedness of the observed strains. Individual animals retained similar or closely related strains. Based on this study, inclusion of TDDGS as a protein and fiber source in cattle diets is not associated with increased maintenance, shedding, or proliferation of resistant strains of generic E. coli, which is an important reservoir of antimicrobial resistance among cattle.

Contamination rates and antimicrobial resistance in bacteria isolated from "grass-fed" labeled beef products

Grass-fed and organic beef products make up a growing share of the beef market in the United States. While processing, animal handling, and farm management play large roles in determining the safety of final beef products, grass-fed beef products are often marketed as safer alternatives to grain-finished beef products based on the potential effects of all-forage diets on host microbiota. We conducted a series of experiments examining bacterial contamination rates in 50 beef products labeled as "grass-fed" versus 50 conventionally raised retail beef products. Coliform concentrations did not differ between conventional and grass-fed beef (conventional: 2.6 log(10) CFU/mL rinsate; grass-fed: 2.7 log(10) CFU/mL rinsate). The percentages of Escherichia coli positive samples did not differ between the two groups (44% vs. 44%). Enterococcus spp. were frequently isolated from both grass-fed beef products (44%) and conventional beef products (62%; p = 0.07). No Salmonella or E. coli O157:H7 isolates were recovered from any of the meat samples. Enterococcus spp. isolates from conventional beef were more frequently resistant to daptomycin and linezolid (p < 0.05). Resistance to some antimicrobials (e.g., chloramphenicol, erythromycin, flavomycin, penicillin, and tetracyline) was high in Enterococcus spp. isolated from both conventional and grass-fed beef. There were no differences in the percentages of antimicrobial resistant E. coli isolates between the two groups. Taken together, these data indicate that there are no clear food safety advantages to grass-fed beef products over conventional beef products.

Escherichia coli O157:H7: recent advances in research on occurrence, transmission, and control in cattle and the production environment

Escherichia coli O157:H7 is a zoonotic pathogen that is an important cause of human foodborne and waterborne disease, with a spectrum of illnesses ranging from asymptomatic carriage and diarrhea to the sometimes fatal hemolytic uremic syndrome. Outbreaks of E. coli O157:H7 disease are often associated with undercooked beef, but there are other sources of transmission, including water, produce, and animal contact, which can often be linked directly or indirectly to cattle. Thus, preharvest control of this pathogen in cattle production should have a large impact on reducing the risk of human foodborne illness. In this review, we will summarize preharvest research on E. coli O157:H7 in cattle and the production environment, focusing on factors that may influence the transmission, prevalence, and levels of this pathogen, such as season, diet, high-level shedders, and animal stress. In addition, we will discuss recent research on the reduction of this pathogen in cattle production, including vaccination, probiotics, bacteriophage, and manure treatments.

Dietary interactions and interventions affecting Escherichia coli O157 colonization and shedding in cattle

Escherichia coli O157 is an important foodborne pathogen affecting human health and the beef cattle industry. Contamination of carcasses at slaughter is correlated to the prevalence of E. coli O157 in cattle feces. Many associations have been made between dietary factors and E. coli O157 prevalence in cattle feces. Preharvest interventions, such as diet management, could reduce the fecal prevalence and diminish the impact of this adulterant. Dietary influences, including grain type and processing method, forage quality, and distillers grains have all been associated with E. coli O157 prevalence. In addition, several plant compounds, including phenolic acids and essential oils, have been proposed as in-feed intervention strategies. The specific mechanisms responsible for increased or decreased E. coli O157 shedding or survival are not known but are often attributed to changes in hindgut ecology induced by diet types. Some interventions may have a direct bacterial effect. Frequently, results of studies are conflicting or not repeatable, which speaks to the complexity of the hindgut ecosystem, variation in animal feed utilization, and variation within feed products. Still, understanding specific mechanisms, driven by diet influences, responsible for E. coli O157 shedding will aid in the development and implementation of better and practical preharvest intervention strategies.