Effects of dried distillers' grain on fecal prevalence and growth of Escherichia coli O157 in batch culture fermentations from cattle

Identification of Contamination Sources and Assessment of Risk Factors Associated with the Occurrence of Escherichia coli O157:H7 on Small-scale Cow-calf Operations in Oklahoma and Louisiana

Escherichia coli O157:H7 is a human pathogen that exists as part of the commensal microflora of cattle and is shed in animal feces. Little is known about the effect of management practices on its occurrence and transmission on small-scale cow-calf operations. Identification of risk factors associated with farm practices could help implement effective measures to control E. coli O157:H7. This study quantified the risk of E. coli O157:H7 occurrence associated with cow-calf farm practices using risk modeling. Management practices of small-scale cow-calf operations in OK and LA were assessed through survey-based research. Fecal, water, sediments and water-trough-swab samples were collected to determine the incidence of E. coli O157:H7, and potential on-farm contamination sources and risk factors identified. Association between the occurrence of pathogen and farm practices was determined using two risk assessment models (I and II). Model I determined the association of E. coli O157:H7 occurrence with water source, water container, feed, cattle breed, and herd density, while Model II determined its association with farm cleanliness. For both models, logistic regression was followed using a two-step approach, univariable and multivariable analysis. In OK and LA, E. coli O157:H7 was present in 5.8% and 8.8% fecal, 4.4% and 9.4% water, 10.3% and 9.6% sediments, and 1.5% and 10.6% water-trough-swab samples, respectively. In Model I, univariable analysis identified water container and feed, whereas multivariable analysis identified feed as a significant risk factor. In Model II, the univariable analysis found cleanliness of cattle-contact areas, such as, alleyways, water-trough, chute and equipment, to be a significant risk factor. In multivariable analysis, only the cleanliness of water-trough was identified to be a significant risk factor. Results from the study could aid in the development of on-farm best management practices for the reduction of E. coli O157:H7.

Reduction of Escherichia coli O157:H7 in Finishing Cattle Fed Corn Genetically Modified to Produce Increased Concentrations of Alpha Amylase in the Corn Kernel

Cattle are recognized as the principal reservoir for Escherichia coli O157:H7 and preharvest food safety efforts often focus on decreasing shedding of this pathogen in cattle feces. Enogen® corn (EC; Syngenta Seeds, LLC) is genetically modified to produce enhanced concentrations of α-amylase in the corn kernel endosperm. Research has demonstrated improvements in feed efficiency for cattle fed EC and research has not yet explored whether improved digestion impacts foodborne pathogen populations in cattle. Therefore, this study explored effects of finishing diets containing EC on Escherichia coli O157:H7 prevalence in cattle. A 2 × 2 factorial experiment was conducted with steers (n = 960) fed diets consisting of 2 types of silage (EC or Control) and grain (EC or Control), fed daily ad libitum. Steers were grouped into 12 blocks by incoming body weight, blocks were randomly assigned to one of four pens, and pens were randomly assigned to one diet. Cattle were sampled using rectoanal mucosal swabs in cohorts of 298-337 cattle per day, for a total of 3 sampling days (15-16 days apart). Escherichia coli O157:H7 prevalence rates ranged from not detected (0/75) to 10.0% (8/80) depending on sampling day. Tests for the silage × corn interaction, and the main effects of silage and corn, were not significant (p > 0.05); however, EC reduced the odds of Escherichia coli O157:H7 prevalence by 43% compared to the control corn diet (p = 0.07). Diets containing EC tended to decrease Escherichia coli O157:H7 prevalence in feedlot cattle; however, this reduction was not significant. Before a conclusion can be drawn about impact of EC on Escherichia coli O157:H7 in cattle, further research is necessary to (1) determine if this tendency is due to increased alpha amylase activity and (2) elucidate impact on Escherichia coli O157:H7 prevalence and concentration, as well as a possible mechanism of action.

Diet and phytogenic supplementation substantially modulate the salivary proteome in dairy cows

Phytogenic compounds may influence salivation or salivary properties. However, their effects on the bovine salivary proteome have not been evaluated. We investigated changes in the bovine salivary proteome due to transition from forage to high-concentrate diet, with and without supplementation with a phytogenic feed additive. Eight non-lactating cows were fed forage, then transitioned to a 65% concentrate diet (DM basis) over a week. Cows were control (n = 4, CON) or supplemented with a phytogenic feed additive (n = 4, PHY). Proteomic analysis was conducted using liquid chromatography coupled with mass spectrometry. We identified 1233 proteins; 878 were bovine proteins, 189 corresponded to bacteria, and 166 were plant proteins. Between forage and high-concentrate, 139 proteins were differentially abundant (P < 0.05), with 48 proteins having a log2FC difference > |2|. The salivary proteome reflected shifts in processes involving nutrient utilization, body tissue accretion, and immune response. Between PHY and CON, 195 proteins were differently abundant (P < 0.05), with 37 having a log2FC difference > |2|; 86 proteins were increased by PHY, including proteins involved in smell recognition. Many differentially abundant proteins correlated (r > |0.70|) with salivary bicarbonate, total mucins or pH. Results provide novel insights into the bovine salivary proteome using a non-invasive approach, and the association of specific proteins with major salivary properties influencing rumen homeostasis. SIGNIFICANCE: Phytogenic compounds may stimulate salivation due to their olfactory properties, but their effects on the salivary proteome have not been investigated. We investigated the effect of high-concentrate diets and supplementation with a phytogenic additive on the salivary proteome of cows. We show that analysis of cows' saliva can be a non-invasive approach to detect effects occurring not only in the gut, but also systemically including indications for gut health and immune response. Thus, results provide unique insights into the bovine salivary proteome, and will have a crucial contribution to further understand animal response in terms of nutrient utilization and immune activity due to the change from forage to a high-energy diet. Additionally, our findings reveal changes due to supplementation with a phytogenic feed additive with regard to health and olfactory stimulation. Furthermore, findings suggest an association between salivary proteins and other components like bicarbonate content.

Effect of Duration of High-Grain Feeding on Chewing, Feeding Behavior, and Salivary Composition in Cows with or without a Phytogenic Feed Supplement

Switching diets from forage to a high-grain (HG) diet increases the risk of rumen fermentation disorders in cattle. However, the effects of the duration of the HG feeding, after the diet switch, on animal behavior and health have received considerably less attention. This experiment primarily aimed to assess the effects of the duration of an HG diet on the chewing, eating, and lying behavior and salivation dynamics in a control group (CON) and a group of cows receiving a phytogenic feed supplement (TRT) at 0.04% (DM basis), which included L-menthol, thymol, eugenol, mint oil, and cloves powder. The experiment was a crossover design with nine non-lactating cows, and two experimental periods with an intermediate washout of four weeks. In each period, the cows were first fed a forage diet for a week to collect baseline measurements representing week 0; then, the diet was switched over a week to HG (65% concentrate), which was fed for four continuous weeks (week 1, week 2, week 3, and week 4 on an HG diet, respectively). The cows were divided in two groups of four and five animals and were randomly allocated to CON or TRT. The data analysis revealed that at the start of the HG feeding, the dry matter intake and the cows’ number of lying bouts increased, but the eating time, rumination time, and meal frequency decreased, resulting in a greater eating rate. We also found that an advanced duration on an HG diet further decreased the rumination time, total chewing time, chewing index, and sorting in favor of short feed particles, with the lowest values in week 4. The feed bolus size increased but feed the ensalivation decreased in week 4 compared to week 0. The dietary switch increased salivary lysozyme activity, and the advanced duration on the HG diet increased salivary pH, but salivary phosphate decreased in weeks 1 and 2 on the HG diet. Supplementation with TRT increased sorting in favor of physically effective NDF (peNDF) in week 2 and increased salivary pH in week 4 on an HG diet. Overall, the negative effects of the HG diet in cattle are more pronounced during the initial stage of the HG feeding. However, several detrimental effects were exacerbated with the cows’ advanced duration on feed, with host adaptive changes still observed after 3 and 4 weeks following the diet switch. The TRT mitigated some of the negative effects through the temporal improvement of the salivary properties and the intake of peNDF, which are known to modulate rumen fermentation.

Rates of evolutionary change of resident Escherichia coli O157:H7 differ within the same ecological niche

Background

Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a pathogen known to reside in cattle feedlots. This retrospective study examined 181 STEC O157:H7 strains collected over 23 years from a closed-system feedlot. All strains were subjected to short-read sequencing, with a subset of 36 also subjected to long-read sequencing.

Results

Over 96% of the strains fell into four phylogenetically distinct clades. Clade membership was associated with multiple factors including stx composition and the alleles of a well-characterized polymorphism (tir 255 T > A). Small plasmids (2.7 to 40 kb) were found to be primarily clade specific. Within each clade, chromosomal rearrangements were observed along with a core phageome and clade specific phages. Across both core and mobile elements of the genome, multiple SNP alleles were in complete linkage disequilibrium across all strains within specific clades. Clade evolutionary rates varied between 0.9 and 2.8 SNP/genome/year with two tir A allele clades having the lowest evolutionary rates. Investigation into possible causes of the differing rates was not conclusive but revealed a synonymous based mutation in the DNA polymerase III of the fastest evolving clade. Phylogenetic trees generated through our bioinformatic pipeline versus the NCBI’s pathogen detection project were similar, with the two tir A allele clades matching individual NCBI SNP clusters, and the two tir T allele clades assigned to multiple closely-related SNP clusters.

Conclusions

In one ecological niche, a diverse STEC O157:H7 population exhibited different rates of evolution that associated with SNP alleles in linkage disequilibrium in the core genome and mobile elements, including tir 255 T > A.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08497-6.

A one health perspective on dairy production and dairy food safety

As the global population approaches 9.7 billion inhabitants by the year 2050, humanity faces enormous challenges to feed, house, and provide basic living requirements for the growing population while preserving the health of wildlife and the ecosystem. Dairy source foods play an important part in providing nutrient and energy dense sources of calories and establishing Bifidobacterium as a keystone species in the gut for positive health outcomes in infants and children. In developed countries, dairy products have a high food safety record when pasteurized and properly processed. However, when milk is consumed unpasteurized, as often occurs in developing countries where regulation and oversight of the dairy industry is lacking, dairy can serve as a vector for zoonotic transmission of disease and can contain adulterants such as antibiotic residues. Here we provide an overview for the importance of dairy source foods for nutrition and with a One Health perspective and discuss the historical events that have resulted in a high standard of dairy food safety in the United States. This review article covers the Origins of One Health, the role of milk in transmission of disease, management practices and regulations to ensure safe dairy products reach consumers, current challenges facing the dairy industry and impacts on public health, and how these standards can be employed in low and middle income countries to improve public health, nutrition and economic benefits to farmers.

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.

Persistence of Escherichia coli O157:H7 and Total Escherichia coli in Feces and Feedlot Surface Manure from Cattle Fed Diets with and without Corn or Sorghum Wet Distillers Grains with Solubles

Feeding corn wet distillers grains with solubles (WDGS) to cattle can increase the load of Escherichia coli O157:H7 in feces and on hides, but the mechanisms are not fully understood. The objective of these experiments was to examine a role for the persistence of E. coli O157:H7 in the feces and feedlot pen surfaces of cattle fed WDGS. In the first study, feces from steers fed 0, 20, 40, or 60% corn WDGS were inoculated with E. coli O157:H7. The E. coli O157:H7 numbers in feces from cattle fed 0% corn WDGS rapidly decreased (P < 0.05), from 6.28 to 2.48 log CFU/g of feces by day 14. In contrast, the E. coli O157:H7 numbers in feces from cattle fed 20, 40, and 60% corn WDGS were 4.21, 5.59, and 6.13 log CFU/g of feces, respectively, on day 14. A second study evaluated the survival of E. coli O157:H7 in feces from cattle fed 0 and 40% corn WDGS. Feces were collected before and 28 days after the dietary corn was switched from high-moisture corn to dry-rolled corn. Within dietary corn source, the pathogen persisted at higher concentrations (P < 0.05) in 40% corn WDGS feces at day 7 than in 0% WDGS. For 40% corn WDGS feces, E. coli O157:H7 persisted at higher concentrations (P < 0.05) at day 7 in feces from cattle fed high-moisture corn (5.36 log CFU/g) than from those fed dry-rolled corn (4.27 log CFU/g). The percentage of WDGS had no effect on the E. coli O157:H7 counts in feces from cattle fed steam-flaked corn-based diets containing 0, 15, and 30% sorghum WDGS. Greater persistence of E. coli O157:H7 on the pen surfaces of animals fed corn WDGS was not demonstrated, although these pens had a higher prevalence of the pathogen in the feedlot surface manure after the cattle were removed. Both or either the greater persistence and higher numbers of E. coli O157:H7 in the environment of cattle fed WDGS may play a part in the increased prevalence of E. coli O157:H7 in cattle by increasing the transmission risk.

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,

Rice Distillers Dried Grain Is a Promising Ingredient as a Partial Replacement of Plant Origin Sources in the Diet for Juvenile Red Seabream (Pagrus major)

This study was designed to test the effects of dietary distillers dried grain (DDG) level on the growth performance, feed utilization, body composition and antioxidant activity of juvenile red seabream (Pagrus major). Six isonitrogenous and isocaloric diets were formulated to contain 0%, 5%, 10%, 15%, 20%, and 25% DDG from rice (designated as DDG0, DDG5, DDG10, DDG15, DDG20, and DDG25), respectively. Juvenile red seabream averaging 10.1±0.05 g were randomly distributed into 400-L tanks in a flow through systems. Three replicate groups of fish were fed one of the experimental diets to visual satiation two times a day for 10 weeks. Survival, weight gain, feed efficiency, protein efficiency ratio and hepatosomatic index of fish were not affected by dietary DDG levels (p>0.05). Proximate and amino acid composition of whole body in juvenile red seabream were not affected by dietary DDG levels (p>0.05). Plasma content of total protein, glucose, cholesterol, glutamic-pyruvic transaminase, phospholipid and triglyceride were not affected by dietary DDG levels (p>0.05). 1, 1-Diphenyl-2-picryl-hydrazyl radical and alkyl radical scavenging activities in plasma and liver of fish were not affected by dietary DDG levels (p>0.05). The results of this experiment suggest that DDG has the potential to replace plant origin ingredients such as wheat flour and corn gluten meal and could be used up to 25% in diet without incurring negative effects on the growth performance of juvenile red seabream.

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.

Fecal shedding in cattle inoculated with Escherichia coli O157:H7 and fed corn or wheat distillers' dried grain with solubles

Feeding corn dried distillers' grain with solubles (DDGS) has been linked to increased fecal shedding of Escherichia coli O157:H7 in cattle. A study was conducted to compare the impact of three diets containing (dry matter basis) 40% corn DDGS, 40% wheat DDGS, or 20% corn and 20% wheat mixed DDGS to a standard barley grain finishing diet on fecal shedding in cattle challenged with a 10(10) CFU mixture of four nalidixic acid-resistant E. coli O157:H7 strains. Rectal grab samples (n = 544) were collected over 70 days and screened for E. coli O157:H7 by direct plating and immunomagnetic bead separation. Feeding diets containing DDGS had no effect (P > 0.05) on the intensity or duration of fecal shedding of E. coli O157:H7 compared with the standard barley grain finishing diet.

Escherichia coli O157:H7 in beef cattle: on farm contamination and pre-slaughter control methods

This paper addresses food safety in beef cattle production, with particular emphasis on factors that affect the prevalence of Escherichia coli O157:H7 in beef cattle and on control methods that have been investigated. Product recalls and foodborne diseases due to this organism continue to occur even though control measures have been under investigation for over 20 years. Most meatborne outbreaks are due to improper food handling practices and consumption of undercooked meat. However, the majority of pathogenic bacteria that can spread at slaughter by cross-contamination can be traced back to the farm rather than originating from the slaughter plant. This would ideally require the adoption of rigorous on-farm intervention strategies to mitigate risks at the farm level. On-farm strategies to control and reduce E. coli O157:H7 at the farm level will reduce the risk of carcass contamination at slaughter and processing facilities although they will not eliminate E. coli O157:H7. The most successful strategy for reducing the risk of contamination of beef and beef products will involve the implementation of both pre- and post-harvest measures.

Influence of wet distillers grains diets on beef cattle fecal bacterial community structure

Background

The high demand for ethanol in the U.S. has generated large stocks of wet distillers grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. Little is known, however, about the potential influence of dietary DG on fecal microbial community structure. A better understanding of the microbial population in beef cattle feces could be an important monitoring tool to facilitate goals of improving nutrient management, increasing animal growth performance and decreasing odors and/or shedding of pathogens. Five diets consisting of a traditional diet fed to finishing beef cattle in the Southern High Plains of Texas-CON (steam-flaked corn control with 0% DG), and four concentrations of DG in the dietary dry matter; 10 C (10% corn-based DG), 5S (5% sorghum-based DG), 10S (10% sorghum DG), and 15S (15% sorghum DG) were fed to steers at the Texas Tech University Burnett Animal Center. Diets were essentially isonitrogenous with a formulated crude protein value of 13.5%.

Results

Fecal grab samples were obtained from 20 steers (n = 4 per diet) and the barcoded DNA pyrosequencing method was used to generate 127,530 16S operational taxonomic units (OTUs). A total of 24 phyla were observed, distributed amongst all beef cattle on all diets, revealing considerable animal to animal variation, however only six phyla (core set) were observed in all animals regardless of dietary treatment. The average abundance and range of abundance, respectively of the core phyla were as follows: Firmicutes (61%, 19 to 83%), Bacteroidetes (28%, 11 to 63%), Proteobacteria (3%, 0.34 to 17.5%), Tenericutes (0.15%, 0.0 to 0.35%), Nitrospirae (0.11%, 0.03 to 0.22%), and Fusobacteria (0.086%, 0.017 to 0.38%). Feeding DG-based diets resulted in significant shifts in the fecal microbial community structure compared with the traditional CON. Four low abundance phyla significantly responded to dietary treatments: Synergistetes (p = 0.01), WS3 (p = 0.054), Actinobacteria (p = 0.06), and Spirochaetes (p = 0.06).

Conclusions

This is, to our knowledge, the first study using this method to survey the fecal microbiome of beef cattle fed various concentrations of wet DG. Comparison of our results with other cattle DNA sequencing studies of beef and dairy cattle feces from a variety of geographical locations and different management practices identifies a core set of three phyla shared across all cattle. These three phyla, in order of relative abundance are; Firmicutes, Bacteroidetes, and Proteobacteria. The presence of large animal-to-animal variation in cattle microbiome was noted in our study as well as by others.

Impact of reducing the level of wet distillers grains fed to cattle prior to harvest on prevalence and levels of Escherichia coli O157:H7 in feces and on hides

Cattle fed finishing diets with wet distillers grains with solubles (WDGS) have been shown to harbor increased Escherichia coli O157:H7 populations in the feces and on the hides. To determine if feeding a lower level of WDGS at the end of the feeding period reduces E. coli O157:H7 load at harvest, 608 heifers were sorted into one of five treatments and fed 0, 40, or 70% WDGS (dry matter basis). For three of the treatments, WDGS was reduced midway through the study. Treatment 0W0W heifers (positive control) were fed a corn grain-based diet continuously, and 40W40W heifers (negative control) were fed 40% WDGS continuously. Heifers subjected to treatments 40W0W, 40W15W, and 70W15W were fed either 40 or 70% WDGS for the first 56 days and switched to 0 or 15% WDGS, respectively, for the last 56 days. Prior to the switch in diets, animals fed diets with 40 or 70% had higher prevalence and percent enumerable fecal samples for E. coli O157:H7. After the dietary switch, animals fed 40W0W, 40W15W, and 70W15W diets had fecal prevalence and percent enumerable samples (33.4 and 6.3%, 31.0 and 9.7%, and 34.9 and 8.4%, respectively) similar to those of animals fed 0W0W diets (10.2 and 3.2%, respectively; P > 0.05), whereas animals fed 40W40W had the highest fecal prevalence and percent enumerable samples (70.1 and 29.2%, respectively; P < 0.05). Similar relationships between the treatments were observed for hide samples. Time after dietary switch was important, as animals fed lower levels had significantly lower fecal prevalence and percent enumerable samples after 56 days, but not after 28 days. The study indicates that cattle can be switched to lower levels of dietary WDGS (15% or less) 56 days prior to harvest to significantly reduce E. coli O157:H7 in feces and on hides.

Effect of backgrounding and transition diets on fecal concentration and strain types of commensalEscherichia coliin beef cattle

Su, R., Munns, K., Beauchemin, K. A., Schwartzkopf-Genswein, K., Jin-Quan, L., Topp, E. and Sharma, R. 2011. Effect of backgrounding and transition diets on fecal concentration and strain types of commensal Escherichia coli in beef cattle. Can. J. Anim. Sci. 91: 449–458. The aim of the study was to assess the effect of four different backgrounding diets [55% corn silage in combination with 40% of either temper rolled barley-grain, wheat dried distillers' grain, corn dried distillers' grain or millrun (dry matter basis)] and a transition diet containing increasing amount of concentrate (60 to 90%) on fecal Escherichia coli in feedlot heifers. Heifers were fed backgrounding forage based diets for 91 d and then were shifted to a transition diet for an additional 18 d. Strain characterization of E. coli (n=224) was carried out at time time points over 109 d and indicated that heifers fed the barley–grain diet shed higher (P<0.001) total and tetracycline-resistant (Tetr) E. coli in the backgrounding phase. Of the total E. coli examined (n=224), 70.3% showed resistance to one or more of the 14 antimicrobials examined, which increased to 82.3% by day 109. Among the recovered E. coli, 23 phenotypes and 154 pulsed field gel electrophoresis patterns grouped into 38 clusters indicative of extensive E. coli diversity in heifers. Although supplementation of 40% barley-grain was correlated to higher total E. coli shedding in the backgrounding phase, the backgrounding diets did not influence strain clustering. Strains collected during the transition phase clustered more closely than those collected during the backgrounding phase. This increased strain clustering with high concentrate inclusion in the transition diet was observed within 18 d of the transition phase. Our study indicated variations in E. coli shedding rates and strain clustering in relation to time and diet.

Naturally colonized beef cattle populations fed combinations of yeast culture and an ionophore in finishing diets containing dried distiller's grains with solubles had similar fecal shedding of Escherichia coli O157:H7

Beef steers (n = 252) were used to evaluate the effects of dietary supplement on fecal shedding of Escherichia coli O157:H7. Seven pens of 9 steers (63 steers per treatment) were fed diets supplemented with or without yeast culture (YC) or monensin (MON) and their combination (YC × MON). YC and MON were offered at 2.8 g/kg and 33 mg/kg of dry matter intake, respectively. Environmental sponge samples (from each pen floor, feed bunk, and water trough) were collected on day 0. Rectal fecal grab samples were collected on days 0, 28, 56, 84, 110, and 125. Samples were collected and pooled by pen and analyzed for presumptive E. coli O157:H7 colonies, which were confirmed by a multiplex PCR assay and characterized by pulsed-field gel electrophoresis (PFGE) typing. On day 0, E. coli O157:H7 was detected in 7.0% of feed bunk samples and 14.3% of pen floor samples but in none of the water trough samples. The 71.4% prevalence of E. coli O157:H7 in fecal samples on day 0 decreased significantly (P < 0.05) over time. E. coli O157:H7 fecal shedding was not associated with dietary treatment (P > 0.05); however, in cattle fed YC and YC × MON fecal shedding was 0% by day 28. Eight Xba I PFGE subtypes were identified, and a predominant subtype and three closely related subtypes (differing by three or fewer bands) accounted for 78.7% of environmental and fecal isolates characterized. Results from this study indicate that feeding YC to cattle may numerically decrease but not eliminate fecal shedding of E. coli O157:H7 at the onset of treatment and that certain E. coli O157 subtypes found in the feedlot environment may persist in feedlot cattle.

Survival of Escherichia coli O157:H7 in ruminal or fecal contents incubated with corn or wheat dried distillers' grains with solubles

Dried distillers' grain with solubles (DDGS) is a by-product of ethanol production, and its use as cattle feed has increased as a result of the expansion of the fuel ethanol industry. However, the inclusion of corn DDGS into feedlot diets may increase the shedding of Escherichia coli O157:H7. This study investigated whether corn or wheat DDGS at 2 concentrations (20% or 40% vs. 100% barley grain) affected the survival of E. coli O157:H7 in incubations of ruminal digesta and feces. Neither the type nor the level of DDGS had any effect on fermentation or the survival of E. coli O157:H7 in ruminal digesta. However, there was a time by DDGS interaction (p < 0.05), where the numbers of E. coli O157:H7 in feces did not differ after 4 or 12 h of incubation but were greater after 24 h in both 40% wheat and 40% corn DDGS as compared with other treatments. Additionally, after 24 h, the numbers of E. coli O157:H7 were greater in fecal incubations with corn DDGS than with wheat DDGS (p < 0.05). The differences in the numbers of E. coli O157:H7 were not attributable to changes in pH or in concentrations of volatile fatty acids in the media. These results suggest that the inclusion of high levels of corn or wheat DDGS in feedlot diets of cattle may encourage the survival of E. coli O157:H7 in feces.

Effects of feeding distillers dried grains with solubles to broilers from 0 to 28 days posthatch on broiler performance, feed manufacturing efficiency, and selected intestinal characteristics

This study evaluated the effect of 2 levels (0 vs. 8%) of distillers dried grains with solubles (DDGS) in a starter broiler diet (0 to 14 d; 45 replicates/treatment) after these same birds were subsequently fed a grower diet (14 to 28 d) with either 0, 7.5, 15, 22.5, or 30% DDGS (9 replicates/treatment). Ross×Ross 308 male broilers were used in this experiment, and evaluation criteria consisted of feed mill parameters, broiler growth, relative liver weight, ileal viscosity, and cecal content count of Clostridium perfringens and Escherichia coli analyzed by both selective media and real-time PCR. Increased inclusion of DDGS resulted in a nonlinear response for production rate (P<0.05), conditioner energy usage (P<0.01), and pellet mill energy usage (P<0.05). Increasing DDGS resulted in a linear decrease in pellet quality (P<0.001) and an increase (P<0.001) in total fines. Inclusion of DDGS decreased (P<0.001) energy usage at the pellet mill and decreased (P<0.05) bulk density of the diets. The DDGS levels fed during the starter phase (0 vs. 8%) had no effect on the broilers at 14 or at 28 d of age. Increasing DDGS inclusion levels during the grower phase resulted in a linear decrease (P<0.001) in BW gain and liver relative weight (P<0.001). A DDGS starter×grower interaction (P<0.05) was observed for feed consumption, in which birds that consumed no DDGS during the starter phase exhibited a decrease in feed consumption with the higher inclusion levels of DDGS during the grower phase, whereas birds that received 8% DDGS during the starter phase were unaffected by DDGS inclusion level in the grower phase. Feed conversion, mortality, ileal viscosity, and cecal C. perfringens and E. coli concentrations were unaffected by DDGS level in the grower diet. The feed intake response suggests a beneficial effect of exposing broiler chicks to DDGS if inclusion levels of 22.5% or higher are to be fed after 14 d of age. However, the data suggest that the young broiler can be negatively affected with inclusion levels of 15% DDGS or higher up to 28 d of age.

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.

Evaluation of bacterial diversity in the rumen and feces of cattle fed different levels of dried distillers grains plus solubles using bacterial tag-encoded FLX amplicon pyrosequencing

Dietary components and changes cause shifts in the gastrointestinal microbial ecology that can play a role in animal health and productivity. However, most information about the microbial populations in the gut of livestock species has not been quantitative. In the present study, we utilized a new molecular method, bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) that can perform diversity analyses of gastrointestinal bacterial populations. In the present study, cattle (n = 6) were fed a basal feedlot diet and were subsequently randomly assigned to 1 of 3 diets (n = 2 cows per diet). In each diet, 0, 25, or 50% of the concentrate portion of the ration was replaced with dried distillers grain (DDGS). Ruminal and fecal bacterial populations were different when animals were fed DDGS compared with controls; ruminal and fecal Firmicute:Bacteroidetes ratios were smaller (P = 0.07) in the 25 and 50% DDG diets compared with controls. Ruminal pH was decreased (P < 0.05) in ruminal fluid from cattle fed diets containing 50% compared with 0% DDGS. Using bTEFAP, the normal microbiota of cattle were examined using modern molecular methods to understand how diets affect gastrointestinal ecology and the gastrointestinal contribution of the microbiome to animal health and production.

Manure odor potential and Escherichia coli concentrations in manure slurries of feedlot steers fed 40% corn wet distillers grains

This study evaluated feeding 0 and 40% wet distillers grains with solubles (WDGS) diets to cattle and the effects on feedlot manure collected from soil-based pens and incubated for 28 d. Steers (n = 603; 261 +/- 32 kg) were fed in eight pens (15 x 150 m) of 75 to 77 steers per pen. Two consecutive experiments were conducted with WDGS--one in which the corn source fed with WDGS was high-moisture and one in which WDGS was fed with dry-rolled corn. We compared odorants (volatile fatty acids [VFAs], aromatic compounds, NH3, H2S) and persistence of Escherichia coli in feedlot manure slurries stored from 0 to 28 d. From both experiments, manure collected from cattle fed 40% WDGS had lower (P < 0.05) total VFAs, including acetate, propionate, and butyrate, all of which continued to be lower to 28 d. However, these slurries had greater concentrations (P < 0.05) of branched-chained VFAs (isobutyrate and isovalerate), especially after 14 d of incubations. Similarly, p-cresol and skatole concentrations tended to be greater in slurries originating from 40% WDGS diets and increased with incubation time. Indole was initially greater in the slurries from 40% WDGS diets; however, it was metabolized by microbes during incubation. Manure slurries from the 40% WDGS diets had greater quantities of H2S, NH3, and P (P < 0.05). Levels of E. coli in 0 and 40% WDGS manure slurries were similar when high-moisture corn was used in the diets. However, when dry-rolled corn was used, E. coli persisted longer in 40% WDGS manure slurries in comparison to 0% WDGS. Results here support earlier studies that suggest feeding WDGS increases odor emissions, N loss, E. coli survival, and surface water contamination due to greater potential P runoff.

Animal- and truckload-level associations between Escherichia coli O157:H7 in feces and on hides at harvest and contamination of preevisceration beef carcasses

Cattle feces and hides contribute to carcass contamination with Escherichia coli O157:H7, ultimately impacting beef safety. Primary objectives of our cross-sectional study were to evaluate associations among fecal, hide, and preevisceration carcass prevalence of E. coli O157:H7 and to assess factors affecting carcass contamination. Fecal, hide, and preevisceration carcass samples were collected from up to 32 cattle on each of 45 truckloads presented to a midwestern U.S. abattoir. Enrichment and selective culture were used to assess fecal, hide, and carcass prevalence, and direct plating was used to identify cattle shedding high levels of E. coli O157:H7 in feces. Fecal, hide, and carcass prevalence of E. coli O157:H7 within truckload were significantly correlated (P < 0.05) with each other. Enriched fecal sample prevalence was 13.8%, and high shedder prevalence was 3.3%; 38.5% of hides and 10.5% of carcasses were positive for E. coli O157:H7. We used logistic regression to assess animal- and truckload-level variables affecting the probability of carcasses testing positive for E. coli O157:H7. All truckload-level predictors significantly affected the probability of an E. coli O157:H7-positive carcass, including presence of a high shedder within the truckload (odds ratio [OR] = 4.0; confidence interval [CI], 1.6 to 10.1), high (>25%) within-truckload fecal prevalence (OR = 19.3; CI, 4.7 to 79.0), and high (>50%) within-truckload hide prevalence (OR = 7.7; CI, 3.1 to 19.6). The only significant animal-level predictor was having a positive hide (OR = 1.6; CI, 1.0 to 2.6). Our results suggest that preharvest interventions for reducing E. coli O157:H7 contamination of carcasses should focus on truckload (cohort)-level and hide mitigation strategies.

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.

Diagnostic microarray for human and animal bacterial diseases and their virulence and antimicrobial resistance genes

Rapid diagnosis and treatment of disease is often based on the identification and characterization of causative agents derived from phenotypic characteristics. Current methods can be laborious and time-consuming, often requiring many skilled personnel and a large amount of lab space. The objective of our study was to develop a spotted microarray for rapid identification and characterization of bacterial pathogens and their antimicrobial resistance genes. Our spotted microarray consists of 489 70mer probes that detect 40 bacterial pathogens of medical, veterinary and zoonotic importance (including 15 NIAID Category A, B and C pathogens); associated genes that encode resistance for antimicrobial and metal resistance; and DNA elements that are important for horizontal gene transfer among bacteria. High specificity and reliability of the microarray was achieved for bacterial pathogens of animal and human importance by validating MDR pathogenic bacteria as pure cultures or by following their inoculation in complex and highly organic sample matrices, such as soil and manure.

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.

Prevalence and level of Escherichia coli O157:H7 in feces and on hides of feedlot steers fed diets with or without wet distillers grains with solubles

The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.

Odorant production and persistence of Escherichia coli in manure slurries from cattle fed zero, twenty, forty, or sixty percent wet distillers grains with solubles

Corn ethanol production removes starch and concentrates the remaining nutrients, including CP and minerals. When wet distillers grains with solubles (WDGS) are fed to cattle in place of corn, CP and minerals often exceed dietary needs. This may increase N emission, P run-off, and odor production. These variables are evaluated in this study. Crossbred steers (n = 160; 434 +/- 8 kg) were assigned in a completely randomized block design to 9 x 9 m pens with concrete floor (10 animals/pen; 4 pens/treatment). Steers were fed a finishing diet that contained 0, 20, 40, or 60% WDGS on a DM basis, and provided 13.3, 15.5, 20.6, or 24.9% CP, respectively. Two kilograms of manure slurry (14 to 23% DM) were collected from each pen monthly (Aug. 20, Sep. 24, and Oct. 22). Samples were analyzed immediately for odorants, DM, pH, NH(3), total alcohol, l-lactate, and concentrations of generic Escherichia coli. After incubation of the samples at 22 degrees C for 2, 4, 7, 10, 15, 21, and 28 d, samples were analyzed for methane production in addition to the above characteristics. Before incubation, NH(3), H(2)S, indole, phenol, isovalerate, isobutyrate, and acetate increased (P < 0.01) with increasing amounts of WDGS in the diet. Other odorants, including skatole, caproate, valerate, butyrate, and propionate, were greater (P < 0.01) in manure slurries from cattle fed 20 or 40% WDGS, compared to 0% WDGS. The l-lactate was greater (P < 0.01) in slurries from cattle fed 0% WDGS (447 mu mol/g of DM) compared with the other treatment slurries (14 to 15 mu mol/g of DM). After incubation, l-lactate contributed to lowered slurry pH (6.3, 7.1, 7.6, and 8.2, respectively, for 0, 20, 40, and 60% WDGS), which inhibited microbial fermentation, E. coli persistence, and methane production. Because of the favorable, more neutral pH in the 40 and 60% WDGS slurries, many of the odorant compounds were rapidly converted to methane during a 28-d static incubation. Escherichia coli O157:H7 inoculated into subsamples of the manure slurries exhibited behavior similar to that of naturally present generic E. coli, surviving in greater numbers longer (P < 0.05) in 20 and 40% WDGS slurries than in 0% WDGS. These data indicate feeding WDGS can increase odorants in manure slurries and extend the persistence of E. coli.