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Foodborne pathogen Campylobacter jejuni has been associated with ruminants. The objectives of this experiment were to determine C. jejuni survivability in mixed in vitro rumen microbial populations and the impact on methane production with or without methane inhibitors 2-bromosulfonate (BES) and/or sodium nitrate. When inoculated into rumen microbial populations without or with 0.5 mM BES, 5.0 mM nitrate or their combination, C. jejuni viability decreased from 4.7 ± 0.1 log10 colony forming units (CFU)/mL after 24 h. Loss of C. jejuni viability was greater (P < 0.05) when incubated under 100% CO2 compared to 50% H2:50% CO2, decreasing 1.46 versus 1.15 log units, respectively. C. jejuni viability was also decreased (P < 0.05) by more than 0.43 log units by the anti-methanogen treatments. Rumen microbial populations produced less methane (P = 0.05) when incubated with than without C. jejuni regardless of whether under 100% CO2 or 50% H2:50% CO2. For either gas phase, nitrate was decreased (13.2 versus 37.9%) by the anti-methanogen treatments versus controls although not always significant. C. jejuni-inoculated populations metabolized 16.4% more (P < 0.05) nitrate under H2:CO2versus 100% CO2. Apparently, C. jejuni can compete for H2 with methanogens but has limited survivability under rumen conditions. [ABSTRACT FROM AUTHOR]

Ionophores and antibiotics have been shown to decrease ruminal methanogenesis both in vitro and in vivo but have shown little evidence toward a sustainable means of mitigation. Feed additive rotation was proposed and investigated for methane, VFA, and microbial population response. In the present study, cannulated steers (n = 12) were fed a moderateforage basal diet in a Calan gate facility for 13 wk. In addition to the basal diet, steers were randomly assigned to 1 of 6 treatments: 1) control, no additive; 2) bambermycin, 20 mg bambermycin/d; 3) monensin, 200 mg monensin/d; 4) the basal diet + weekly rotation of bambermycin and monensin treatments (B7M); 5) the basal diet + rotation of bambermycin and monensin treatments every 14 d (B14M); and 6) the basal diet + rotation of bambermycin and monensin treatments every 21 d (B21M). Steers were blocked by weight in a randomized complete block design where the week was the repeated measure. Rumen fluid was collected weekly for analysis (n = 13), and results were normalized according to individual OM intake (OMI; kg/d). Potential activity of methane production was not significantly different among treatments (P > 0.05). However, treatment tended to affect the CH4-to-propionate ratio (P = 0.0565), which was highest in the control and lowest in the monensin, B21M, and B14M treatments (0.42 vs. 0.36, 0.36, and 0.33, respectively). The CH4:propionate ratio was lowest in wk 2 and 3 (P < 0.05) but the ratio in wk 4 to 12 was not different from the ratio in wk 0. Week also affected total VFA, with total VFA peaking at wk 3 and plummeting at wk 4 (4.02 vs. 2.86 mM/kg OMI; P < 0.05). A significant treatment × week interaction was observed for the acetate-to-propionate (A:P) ratio, where bambermycin- and rotationally fed steers did not have a reduced A:P ratio compared with monensin-fed steers throughout the feeding period (P < 0.0001). Microbial analysis revealed significant shifts, but several predominant classes showed adaptation between 4 and 6 wk after additive initiation. There was no significant evidence to suggest that rotations of monensin and bambermycin provided additional benefits to steers consuming a moderate-forage diet at the microbial/animal and environmental level versus those continuously fed. [ABSTRACT FROM AUTHOR]

Effects of monensin withdrawal and cattle subspecies on the utilization of bermudagrass hay (14.3% CP, 72.3% NDF, and 36.9% ADF) were evaluated using ruminally cannulated steers (5 Bos taurus indicus [BI] and 5 Bos taurus taurus [BT]). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments consisted of either 0 mg·steer−1·d−1 monensin with no previous monensin feeding (CON) or withdrawal from 200 mg·steer−1·d−1 monensin (MON) fed individually in 0.91 kg dried distillers’ grains with solubles for 42 d. Withdrawal was evaluated for a 28-d period. Ruminal fluid was collected 2 h after feeding on d 0, 1, 4, 7, 14, and 21 after withdrawal for determination of pH, VFA, ruminal NH3–N (RAN), rate of NH3 production, and CH4 production rate. Hay, ort, and fecal grab samples were collected d 23 through 28 after withdrawal for determination of intake and digestion. No subspecies × monensin, subspecies × day, or subspecies × monensin × day interactions were observed (P ≥ 0.11). An effect of day after monensin withdrawal was observed (P < 0.01) for total VFA concentration, with an increase following withdrawal followed by a decrease and then stabilization. Monensin × day after monensin withdrawal interactions (P ≤ 0.01) were observed for the acetate:propionate (A:P) ratio and molar percent of acetate and propionate. There was a decrease in molar percent of propionate between d 1 and 4 from 19.1 to 18.0; however, it remained greater (P ≤ 0.10) for MON than CON through d 7. Withdrawal increased molar percent of acetate from 68.3 to 69.8 between d 0 and 4 for MON steers. The A:P ratio was less (P ≤ 0.01) on d 0 for MON than for CON (3.4 vs. 4.0), but by d 4, it increased to 3.8 and was not different (P = 0.14) from CON. By d 14, no differences (P ≥ 0.88) remained for acetate, propionate, or the A:P ratio. After monensin withdrawal, monensin reduced (P < 0.01) RAN by 12.3% (2.09 vs. 1.83 mM for CON and MON, respectively). Monensin withdrawal and cattle subspecies had no effect (P ≥ 0.23) on rate of NH3 production or CH4 production rate. Monensin withdrawal had no effect (P ≥ 0.45) on intake or digestibility parameters. Greater forage OM intake (P = 0.09; 21.2 vs. 19.2 g/kg BW) and OM digestibility (P < 0.01; 72.4 vs. 63.0%) resulted in greater (P < 0.01) total digestible OM intake (16.8 vs. 13.2 g/kg BW) in BT steers than in BI steers. These results suggest that BT steers are better able to utilize bermudagrass hay than BI steers. Upon monensin withdrawal, steers previously fed monensin continue to have a reduced A:P ratio for at least 7 d. [ABSTRACT FROM AUTHOR]

Effects of monensin inclusion and cattle subspecies on utilization of bermudagrass hay (13.7% CP, 77.3% NDF, and 38.8% ADF) were evaluated using ruminally cannulated steers (5 Bos taurus indicus [BI] and 5 Bos taurus taurus [BT]; 398 kg BW). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments were 0 (CON) or 200 mg·steer−1·d−1 monensin (MON) in 0.91 kg dried distillers’ grains with solubles. Periods were 70 d in length: 20 d of adaptation, 22 d of sample collection, and 28 d for withdrawal of treatment. Steers were group housed during adaptation and moved to individual covered pens for sampling. Hay, ort, and fecal grab samples were collected d 21 through 25 for determination of intake and digestion. Ruminal fluid was collected with a suction strainer 0, 2, 4, 8, and 12 h after feeding on d 42 for pH, VFA, and ruminal NH3–N (RAN) analysis. Additionally, at h 2, ruminal fluid and contents were collected for determination of rate of NH3 production and CH4 production rate. No subspecies × monensin interactions were observed (P ≥ 0.12). Monensin had no effect (P ≥ 0.16) on intake or digestibility parameters. No subspecies effect (P ≥ 0.11) was observed for forage OM intake, total OM intake, or OM digestion. Total digestible OM intake tended to be greater (P = 0.06) for BT steers than for BI steers (14.0 vs. 12.2 g/kg BW). There was an effect of hour after feeding (P ≤ 0.01) on pH, total VFA, acetate:propionate ratio, and molar percent acetate and propionate. Total VFA concentration was greater (P = 0.01) in CON steers than in MON steers (66.5 vs. 62.0 mM). Monensin decreased molar percent acetate (P = 0.02) from 72.5 to 71.2% and increased molar percent propionate (P < 0.01) from 16.9 to 18.7%, resulting in a reduced (P < 0.01) acetate:propionate ratio (from 4.34 to 3.85). Although not significantly (P = 0.19), monensin numerically reduced the CH4 production rate by 15.8%. Greater (P = 0.07) CH4 production rate tended to be observed in BI steers than in BT steers (21.4 vs. 16.6 μmol CH4·mL−1·h−1, respectively). Monensin had no effect (P ≥ 0.32) on pH, RAN, or rate of NH3 production. A subspecies × hour after feeding interaction was observed for RAN, with BT having greater RAN at h 0 and 4, whereas BI had greater RAN at h 2, 8, and 12. Overall, monensin decreased the acetate:propionate ratio and total VFA concentration but had no effect on forage utilization. Bos taurus indicus steers consumed less digestible OM and had a greater CH4 production rate compared with BT steers, suggesting BT were better able to utilize the available forage resource than BI. [ABSTRACT FROM AUTHOR]

English ? Continental heifers (n = 180) were sourced in 2 loads (219.3 ± 16.0 and 221.4 ± 16.4 kg, respectively) from commercial auction barns to study the effects of feeding dehydrated citrus pulp (DCP) on feedlot performance of newly received heifers. A completely randomized block design was used with BW nested within arrival load and blocked by BW into 3 dietary treatments (36 pens, 5 heifers/ pen, 12 blocks, 3 pens/block, and 12 pens/treatment). Treatment diets contained 1) 0% DCP (control diet [CON]), 2) 10% DCP, or 3) 20% DCP on a DM basis. Diets containing DCP were exchanged with steamflaked corn on a 1:1 basis. Cattle were fed a 63, 73, and 83% concentrate diet from d 0 to 28, d 28 to 42, and d 42 to 56, respectively. Over the 56-d trial period, as the amount of dietary DCP increased, DMI decreased (P = 0.01), ADG decreased (P < 0.01), and G:F decreased (P = 0.02). From d 0 to 28, there was no difference in the observed minus the predicted NEg of the diet (P = 0.73); from d 28 to 42, there was a linear increase in NEg favoring DCP treatments (P < 0.01); and from d 42 to 56, there was a linear decrease in NEg against the DCP treatments (P < 0.01). At the conclusion of the trial, a subset of heifers (n = 22; 307.89 ± 3.32 kg on d 63) were used to evaluate blood metabolite concentrations before and after a lipopolysaccharide (LPS) challenge. On d 63, heifers were fitted with jugular catheters and moved into individual stalls. On d 64, heifers were intravenously challenged with LPS (0.5 µg/kg BW), and blood samples were collected every 0.5 h from -2 to 8 h and at 24 h relative to the LPS challenge (0 h). Serum glucose, serum urea nitrogen (SUN), and NEFA concentrations were determined. Cattle lost less weight at both 24 and 72 h after the LPS challenge with increasing DCP percentage (P < 0.01). Glucose (P = 0.12) and NEFA (P = 0.13) concentrations did not differ before the LPS challenge; however, there was a treatment effect for SUN, with elevated concentrations of SUN in CON cattle (P < 0.01). After the LPS challenge, DCP-fed cattle had reduced glucose, elevated NEFA, and reduced SUN concentrations (P ≤ 0.01). Results indicate that dietary DCP modulated metabolite concentrations in heifers following an endotoxin challenge and affected feedlot performance when incorporated in receiving diets in replacement of corn. Future studies will need to address strategies to increase DMI or explore levels of DCP less than 10% in the diet of newly received heifer calves. [ABSTRACT FROM AUTHOR]

Pathogenic bacteria can live asymptomatically within and on cattle and can enter the food chain but also can be transmitted to humans by fecal or direct animal contact. Reducing pathogenic bacterial incidence and populations within live cattle represents an important step in improving food safety. A broad range of preslaughter intervention strategies are being developed, which can be loosely classified as 1) directly antipathogen strategies, 2) competitive enhancement strategies (that use the microbiome's competitive nature against pathogens), and 3) animal management strategies. Included within these broad categories are such diverse methods as vaccination against foodborne pathogens, probiotics and prebiotics, bacterial viruses (i.e., bacteriophages), sodium chlorate feeding, and dietary and management changes that specifically alter the microbiome. The simultaneous application of 1 or more preharvest strategies has the potential to reduce human foodborne illnesses by erecting multiple hurdles preventing entry into humans. However, economic factors that govern producer profitability must be kept in mind while improving food safety. [ABSTRACT FROM AUTHOR]

Because challenge models to infect peripheral lymph nodes (PLNs) with Salmonella have not been reported, we performed a series of experiments to develop and refine challenge models to evaluate an intervention applied at the animal level and to provide initial estimates of efficacy of an intervention (i.e., a vaccine) to aid in the design of future studies. In each of four experiments, steers (control or vaccinated) were inoculated with Salmonella strains Montevideo or Newport, and in experiment IV, Salmonella Senftenberg was also used. Calves were euthanized 14 to 42 days postinoculation, and PLNs were collected. In the first experiment, calves were challenged with ~1010 Salmonella cells, and few treatment differences were observed 14 days postchallenge. However, by day 21, Salmonella Newport was recovered from fewer vaccinated calves than control calves (P < 0.05). In experiment II, calves were challenged with ~107 Salmonella cells and, after two necropsies (14 and 28 days postchallenge), only one lymph node was Salmonella positive; therefore, the study was terminated. In experiment III, calves were again challenged with ~1010 Salmonella cells, and no significant effect of vaccine was observed in calves challenged with Montevideo or Newport strains. A transdermal route of challenge was explored in experiment IV, using a 10-lancet, allergy testing instrument. Sixteen steers were challenged with either Salmonella Newport or Salmonella Montevideo (Salmonella Newport right legs; Salmonella Montevideo left legs), and all steers were challenged on the lower abdomen with Salmonella Senftenberg. Transdermal inoculation resulted in predictably Salmonella-positive PLNs, and a modest vaccine effect was detected. Because it is well tolerated by the calves and results in predictable and regionally specific Salmonella recovery from PLNs, the transdermal route of challenge may be preferred by researchers wishing to evaluate the impact of interventions designed to reduce the carriage of Salmonella in PLNs. [ABSTRACT FROM AUTHOR]

Recent investigations have found that Salmonella can be routinely recovered from peripheral lymph nodes (PLNs) of cattle presented for harvest. When contained within the PLNs, this foodborne pathogen is protected from currently used postharvest, in-plant intervention strategies and, therefore, PLNs harboring Salmonella may be a potential contaminant of ground beef. The objective of this work was to develop a challenge model that effectively and repeatedly results in Salmonella-positive PLNs. A 10-lancet skin-allergy instrument was inoculated with Salmonella, and calves were inoculated intra- and/or transdermally by applying the device over various ventral regions of the skin. Salmonella was successfully and predictably recovered from region-specific PLNs up to 8 days postchallenge. Furthermore, serotypes inoculated within specific regions were only recovered from the PLNs draining those regions. This model provides a method to predictably infect PLNs with Salmonella. Further, this model makes it possible to determine the duration of infection and to evaluate candidate interventions that may shorten the duration of infection. [ABSTRACT FROM AUTHOR]

Robert Hungate, considered the father of rumen microbiology, was the first to initiate a systematic exploration of the microbial ecosystem of the rumen, but he was not alone. The techniques he developed to isolate and identify cellulose-digesting bacteria from the rumen have had a major impact not only in delineating the complex ecosystem of the rumen but also in clinical microbiology and in the exploration of a number of other anaerobic ecosystems, including the human hindgut. Rumen microbiology has pioneered our understanding of much of microbial ecology and has broadened our knowledge of ecology in general, as well as improved the ability to feed ruminants more efficiently. The discovery of anaerobic fungi as a component of the ruminal flora disproved the central dogma in microbiology that all fungi are aerobic organisms. Further novel interactions between bacterial species such as nutrient cross feeding and interspecies H2 transfer were first described in ruminal microorganisms. The complexity and diversity present in the rumen make it an ideal testing ground for microbial theories (e.g., the effects of nutrient limitation and excess) and techniques (such as 16S rRNA), which have rewarded the investigators that have used this easily accessed ecosystem to understand larger truths. Our understanding of characteristics of the ruminal microbial population has opened new avenues of microbial ecology, such as the existence of hyperammonia-producing bacteria and how they can be used to improve N efficiency in ruminants. In this review, we examine some of the contributions to science that were first made in the rumen, which have not been recognized in a broader sense. [ABSTRACT FROM AUTHOR]

The objective of this experiment, part of a larger study, was to investigate changes in rumen bacterial, archaeal, and fungal diversity in cows fed medium-chain saturated fatty acids. In the main study, 6 lactating dairy cows were dosed intraruminally with 240 g/(cow.d) of stearic (SA, control), lauric (LA), or myristic (MA) acid in a replicated 3 × 3 Latin square design trial. Experimental periods were 28 d, and cows were transfaunated between periods. Lauric acid decreased protozoal counts in the rumen by 96% compared with SA and MA (compared with SA, MA had no effect on ruminal protozoa). Whole ruminai contents samples were collected 2, 4, 6, 8, 10, 14, 18, and 24 h after the morning feeding on d 23 of each experimental period, stored frozen, and later composited by cow and period for microbial profile analyses, which involved tag-encoded flexible (FLX) amplicon pyrosequencing to provide diversity analyses of gastrointestinal bacterial, archaeal, and fungal populations of the cattle. The LA treatment, either directly or through its effect on protozoa, had a profound effect on the microbial ecology of the rumen. Ruminai populations of Prevotella, Bacteroides, and Enterorhabdus were decreased (P = 0.04 to P < 0.001) by more than 2-fold in LA treatments compared with SA, and Clostridium populations were decreased (P = 0.01) in LA- compared with MA-treated cows. The proportion of Ruminococcus was not affected by treatment, although the LA treatment had the least proportion of Ruminococcus. Proportions of Eubacterium, Butyrivibrio, Olsenella, and Lactobacillus genera were increased (P = 0.03 to 0.01) by LA compared with MA or SA. The LA treatment, possibly through its effect on protozoa physically associated with archaea, resulted in an increase (P = 0.01) in the archaeal methanogenic genus Methanosphaera and a decrease (P = 0.01) in Methanobrevibacter. Few changes in fungal populations caused by treatment were detected. Collectively, results indicate that LA, either through antiprotozoal or direct antimicrobial effects, altered bacterial and archaeal populations in the rumen of dairy cows, but effects on fungal populations were not clear. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examines the effects of brown midrib (bm3) and conventional (DP) corn silages as well as the inclusion of dried distillers' grains with solubles (DDGS) on milk production and N utilization in dairy cows. It shows that total tract fiber digestibility was higher for cows consuming bm3 compared with DP hybrid. It reveals that milk protein yield was positively influenced by bm3 corn silage and the inclusion of DDGS.

Strategies aimed at reducing fecal shedding of Salmonella and other foodborne pathogens may be effective for limiting transmission of pathogens from food animals to humans. The objective of this study was to determine the effectiveness of gallium maltolate (GaM) against Salmonella in vitro and to determine whether oral administration of GaM would reduce fecal shedding of Salmonella in cattle. Gallium is a semimetal exhibiting antimicrobial properties against some pathogenic bacteria, including Salmonella, by exploiting their need for iron to survive and replicate. In vitro growth studies were performed in pure cultures of Salmonella and in mixed cultures from ruminal fluid. Inclusion of GaM in culture medium or in mixed cultures of ruminal fluid resulted in a significant reduction in growth of Salmonella, suggesting that GaM may be effective for limiting growth and survival in vivo. Therefore, we subsequently administered two doses of GaM to Holstein steers, experimentally infected them with Salmonella, and quantitatively and qualitatively monitored fecal shedding at 12-h intervals. Sixty hours after beginning treatment, cattle were euthanized, and luminal contents and tissue were aseptically harvested from the rumen, jejunum, spiral colon, cecum, and rectum. The luminal contents were processed for quantitative and qualitative analysis of the challenge strains of Salmonella, and tissue samples were enriched and plated for qualitative analysis. We found no significant differences between control and treated animals in quantitative levels of Salmonella in the feces or the luminal contents. Likewise, we observed no pattern between control and treated animals in the frequency of positive or negative results from enriched feces, luminal contents, or tissue samples. These results suggest that GaM was not effective for reducing Salmonella in cattle. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Laying hens are typically induced to molt to begin a new egg-laying cycle by withdrawing feed for up to 12 to 14 d. Fasted hens are more susceptible to colonization and tissue invasion by Salmonella enterica serovar Enteritidis. Much of this increased incidence in fasted hens is thought to be due to changes in the native intestinal microflora. An alternative to feed withdrawal involves feeding alfalfa meal crumble to hens, which is indigestible by poultry but provides fermentable substrate to the intestinal microbial population and reduces Salmonella colonization of hens compared with feed withdrawal. The present study was designed to quantify differences in the cecal microbial population of hens (n = 12) fed a typical layer ration, undergoing feed withdrawal, or being fed alfalfa crumble by using a novel tag bacterial diversity amplification method. Bacteroides, Prevotella, and Clostridium were the most common genera isolated from all treatment groups. Only the ceca of hens undergoing feed withdrawal (n = 4) contained Salmonella. The number of genera present was greatest in the alfalfa crumble-fed group and least in the feed withdrawal group (78 vs. 54 genera, respectively). Overall, the microbial diversity was least and Lactobacillius populations were not found in the hens undergoing feed withdrawal, which could explain much of these hens' sensitivity to colonization by Salmonella. [ABSTRACT FROM AUTHOR]

The last century of food animal agriculture is a remarkable triumph of scientific research. Knowledge derived through research has resulted in the development and use of new technologies that have increased the efficiency of food production and created a huge animal production and food manufacturing industry capable of feeding the US population while also providing significant quantities of high-quality food for export to other countries. Although the US food supply is among the safest in the world, the US Center for Disease Prevention and Control estimates that 76 million people get sick, more than 300,000 are hospitalized, and 5,000 die each year from foodborne illness. Consequently, preventing foodborne illness and death remains a major public health concern. Challenges to providing a safe, abundant, and nutritious food supply are complex because all aspects of food production, from farm to fork, must be considered. Given the national and international demand and expectations for food safety as well as the formidable challenges of producing and maintaining a safe food supply, food safety research and educational programs have taken on a new urgency. Remarkable progress has been made during the last century. Wisdom from a century of animal agriculture research now includes the realization that on-farm pathogens are intricately associated with animal health and well-being, the production of highquality food, and profitability. In this review, some of the developments that have occurred over the last few decades are summarized, including types, sources, and concentrations of disease-causing pathogens encountered in food-producing animal environments and their association with food safety; current and future methods to control or reduce foodhorne pathogens on the farm; and present and future preharvest food safety research directions. Future scientific breakthroughs will no doubt have a profound impact on animal agriculture and the production of high-quality food, but we will also be faced with moral, ethical, and societal dilemmas that must be reconciled. A strong, science-based approach that addresses all the complex issues involved in continuing to improve food safety and public health is necessary to prevent foodborne illnesses. Not only must research be conducted to solve complex food safety, issues, but results of that research must also be communicated effectively to producers and consumers. [ABSTRACT FROM AUTHOR]

The microbial population of the intestinal tract is a complex natural resource that can be utilized in an effort to reduce the impact of pathogenic bacteria that affect animal production and efficiency, as well as the safety of food products. Strategies have been devised to reduce the populations of food-borne pathogenic bacteria in animals at the on-farm stage. Many of these techniques rely on harnessing the natural competitive nature of bacteria to eliminate pathogens that negatively impact animal production or food safety. Thus feed products that are classified as probiotics, prebiotics and competitive exclusion cultures have been utilized as pathogen reduction strategies in food animals with varying degrees of success. The efficacy of these products is often due to specific microbial ecological factors that alter the competitive pressures experienced by the microbial population of the gut. A few products have been shown to be effective under field conditions and many have shown indications of effectiveness under experimental conditions and as a result probiotic products are widely used in all animal species and nearly all production systems. This review explores the ecology behind the efficacy of these products against pathogens found in food animals, including those that enter the food chain and impact human consumers. [ABSTRACT FROM AUTHOR]

Aim: To estimate the distribution and prevalence of both Escherichia coli O157 and O157:H7-infecting bacteriophages within a 50 000 head commercial beef feedlot. Methods and Results: Escherichia coli O157 was detected in ∼27% of the individual samples, distributed across seven of the 10 pens screened. In a simple initial screen to detect O157:H7-infecting phages, none were detected in any pen or individual sample. In contrast, after a series of enrichment procedures O157:H7-infecting phages were detected in every pen and in the majority of the samples from most pens; virulent bacteriophages active against E. coli O157:H7 were detected post-enrichment from 39/60 (65%) of the feedlot samples, and 58/60 (∼97%) contained phage that infected E. coli B or O157:H7. Conclusions: The data we present here indicates that we may be grossly underestimating the prevalence of O157:H7-infecting phages in livestock if we simply screen samples and that enrichment screening is required to truly determine the presence of phages in these ecosystems. Significance and Impact of the Study: Our data suggest that O157:H7-infecting phages may play a role in the ecology and transient colonization of cattle by E. coli O157:H7. Further, this and previous data suggest that before starting in vivo pathogen eradication studies using phage or any other regime, test animals should be enrichment screened for phage to avoid erroneous results. [ABSTRACT FROM AUTHOR]

Monensin and tylosin have activity against gram-positive bacteria, and it has been theorized that their effects on the intestinal environment may promote proliferation of gram-negative bacteria such as Escherichia coli. Effects of these antibiotics on the shedding of E. coli O157:H7 were studied in a feedlot environment, using 32 finishing steers. A diet containing 85% barley grain, 10% barley silage, and 5% supplement was amended with 33 ppm monensin, 11 ppm tylosin, both of these additives, or no additives (control). All steers were orally inoculated with 1010 CFU of a mixture of four strains of nalidixic acid-resistant E. coli O1 57:H7. Fecal (grab), oral (mouth swab) and water, water-water bowl interface, feed, and pen floor fecal pat samples were collected weekly for 12 weeks. Prevalence of E. coli O157:H7-positive fecal grab samples did not differ (P = 0.26) among treatments, nor did the rate (P = 0.81) or duration (P = 0.85) of shedding of the organism. Fecal grab samples were positive for E. coli O157:H7 more frequently (P < 0.001) than were oral swabs. More (P = 0.02) E. coli O157:H7-positive oral swabs were recovered from the tylosin group than from controls. E. coli O157:H7 was not detected in any of 47 water samples, but was present in 1 of 47 water bowl swabs, 7 of 48 feed samples, and 36 of 48 fecal pats. Pulsed-field gel electrophoresis suggested that differences existed among inoculated strains in their ability to persist in animals and in the environment. However, this study revealed no evidence that dietary inclusion of monensin or tylosin, alone or in combination, increased fecal shedding of E. coli O157:H7 or its persistence in the environment. [ABSTRACT FROM AUTHOR]

We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH), and nitroethane (NE) on growth and survivability of Listeria monocyrogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For example, specific growth rates of L. monocytogenes strain 18 declined (P < 0.05) 76, 60, and 29% from controls during aerobic culture at 37°C in brain heart infusion broth containing 10 mM 2NPOH, 2NEOH, or NE, respectively. Mean specific growth rate for the controls incubated likewise without added nitrocompound was 0.62 ± 0.02 h-1. Specific growth rates of L. monocytogenes Scott A decreased (P < 0.05) 67, 45, and 11%, respectively, from controls (0.67 ± 0.02 h-1) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30°C were reduced (P < 0.05) 76, 60, and 30%, respectively, and were reduced (P < 0.05) 78, 23, and 23% during anaerobic culture at 30°C in brain heart infusion broth containing 15 mM 2NPOH, 2NEOH, or NE (control rates ranged from 0.37 ± 0.07 to 0.74 ± 0.05 h-1). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 months at 4°C) in brain heart infusion broth containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH, and NE against L. monocyrogenes in vitro. [ABSTRACT FROM AUTHOR]

Salmonella is one of the most serious foodborne pathogenic bacteria in the United States, causing an estimated 1.3 million human illnesses each year. Dairy cows can be reservoirs of foodborne pathogenic bacteria, including Salmonella spp.; it is estimated that from 27 to 31% of dairy herds across the United States are colonized by Salmonella. The present study was designed to examine the occurrence of Salmonella spp. on dairies and to examine the serotypic diversity of Salmonella isolates on sampled dairies from across the United States. Fecal samples (n = 60 per dairy) were collected from 4 dairies in each of 4 states for a total of 960 fecal samples representing a total population of 13,200 dairy cattle. In the present study, 93 of 960 samples (9.96%) collected were culture-positive for Salmonella enterica. At least one Salmonella fecal-shedding cow was found in 9 of the 16 herds (56%) and the within-herd prevalence varied in our study from 0% in 7 herds to a maximum of 37% in 2 herds, with a mean prevalence among Salmonella-positive herds of 17%. Seventeen different serotypes were isolated, representing 7 different Salmonella serogroups. There were 2 or more different serogroups and serotypes present on 7 of the 9 Salmonella-positive farms. Serotypes Montevideo and Muenster were the most frequent and widespread. From our data, it appears that subclinical colonization with Salmonella enterica is relatively common on dairy farms and is represented by diverse serotypes on US dairy farms. [ABSTRACT FROM AUTHOR]

Heat stress and dusty conditions are common challenges for cattle during the summer, and a typical method of alleviating these problems involves sprinkling cattle and pens with water. The effect of sprinkling water on the incidence of zoonotic pathogens has not been previously studied. Four pens of heifers (n = 41) were cooled using sprinklers, and four pens (n = 43) served as controls. Heifers were crossbred Charolais, with white and red hair coats. Sprinkling was initiated when cattle were on full concentrate feed (July). Fecal samples, hide swipes, and BW were collected on d 0, 28, 63, 95, and 98. Average daily gain, DMI, and G:F were calculated, and carcass traits were collected 36 h after processing. Performance data were analyzed as a randomized complete block design, and zoonotic pathogen data were analyzed using X² analysis. Sprinkling tended (P = 0.054) to increase the incidence of fecal Salmonella spp. populations on d 98, but simultaneously tended to decrease (P = 0.058) the Escherichia coli 0157:H7 incidence on hides on d 98. The most prevalent Salmonella serovars in this study were Kentucky, Muenster, Meleagridis, and Cerro. Performance measures and carcass traits did not differ between treatments (P> 0.10). Under our conditions, sprinkling cattle with water did not affect the incidence of zoonotic pathogens in feces or on hides. [ABSTRACT FROM AUTHOR]

Escherichia coli O157:H7 is a virulent foodborne pathogen that causes severe human illness and inhabits the intestinal tract of food animals. Colicins are antimicrobial proteins produced by E. coli strains that inhibit or kill other E. coli. In the present study, the efficacy of three pore-forming colicins (E1, N, and A) were quantified in vitro against E. coli O157:H7 strains 86–24 and 933. Colicins E1 and N reduced the growth of E. coli O157:H7 strains, but the efficacy of each colicin varied among strains. Colicin E1 was more effective against both strains of E. coli Ot57:H7 than colicins A and N and reduced (P < 0.05) populations of E. coli O157:H7 at concentrations <0.1 μg/ml. These potent antimicrobial proteins may potentially provide an effective and environmentally sound preharvest strategy to reduce E. coli O157:H7 in food animals. [ABSTRACT FROM AUTHOR]

Examines the effects of dietary manipulations on Escherichia coli populations in cattle. Information on gastric shock survival; Effects of management strategies on Escherichia coli populations; Importance of the cleanliness of animals.

The objective of the current research was to determine if feeding the citrus by-products D-limonene (DL) and citrus molasses would reduce the concentration and prevalence of Salmonella in weanling pigs experimentally infected with Salmonella Typhimurium. Twenty crossbred weanling pigs (average body weight [BW], 19.9 kg) were randomly assigned to one of four treatments: control, low-dose DL (1.5 ml/kg of BW per day), high-dose DL (3.0 ml/kg of BW per day), and citrus molasses (0.05 kg/kg of BW per day). Treatments were administered in the feed (twice daily) for 7 days, with one-half of the dose administered at each feeding. Fecal samples were collected twice daily (prior to administration of treatment) and cultured for quantitative and qualitative determination of the challenge strain of Salmonella. Upon termination of the study, pigs were euthanized and tissues from the stomach, ileum, cecum, spiral colon, and rectum, as well as luminal contents, were collected. In addition, the popliteal and ileocecal lymph nodes and liver, spleen, and tonsil tissue were collected for qualitative Salmonella culture. No significant treatment differences (P > 0.05) were observed among treatments for fecal concentration or prevalence of Salmonella throughout the 7-day collection period. Likewise, no treatment differences (P > 0.05) were observed for any of the tissue or luminal content samples collected. Salmonella was not cultured from the muscle-bound popliteal lymph node but was cultured from the mesenteric ileocecal lymph nodes. While there were no effects in the current experiment, future research may examine the effect of a lower challenge dose and/or different administration (dose or duration) of the citrus by-products. [ABSTRACT FROM AUTHOR]

Escherichia colt O157:H7 is a foodborne pathogenic bacterium that can reside undetected in the gastrointestinal tract of cattle because colonization by this bacterium is asymptomatic. Recent research has indicated that swine can carry and transmit this pathogen as well. The development of more advanced and sensitive detection techniques has improved the limit of detection and increased sensitivity for this important pathogen. This study was undertaken to determine the prevalence of E coli O157 in cattle and swine in Mexico with the more sensitive detection technique of immunomagnetic bead separation. Samples (n = 60 per farm) were taken from four cattle and four swine farms (n = 240 cattle samples, n = 240 swine samples) located throughout central Mexico in October 2001. The prevalence of E. colt O157 was found to be only 1.25% on cattle farms and 2.1 % on swine farms. The prevalence in cattle in this study is lower than that reported in the United States and could be related to the lower reported prevalence of E. coli O157 in humans in Mexico. However, further research is needed to verify prevalence throughout other regions of Mexico, as well as prevalence during other seasons of the year. [ABSTRACT FROM AUTHOR]

Live yeast (LY) supplementation to ruminants has been shown to increase nutrient digestibility and improve the rumen environment by increasing its pH in dairy cows. Few studies have determined the impact of LY in the rumen of growing cattle receiving high-concentrate diets. This study was designed to evaluate the effects of LY-(Saccharomyces cerevisiae) Actisaf (Phileo Lesaffre Animal Care) on rumen pH and dry matter digestibility during three feeding phases [grower (GRW), transition (TRANS), and finisher (FIN)]. Eight ruminally cannulated cattle (n=4 steers and n=4 heifers) were blocked by sex into two pens containing Calan gate feeders and received a standard diet (13.7% CP, 42.4% NDF, 88% DM) without LY for 10 d (d -10 to d -1). On d 0, each animal was randomly assigned to one treatment [control (CON), LY1 (2.5 g/d per head), LY2 (5 g/d per head), or LY3 (10 g/d per head)], and fed every morning (0800) for 55 d. Each of the three diets (GRW, TRANS, and FIN) were fed sequentially as follows: GRW for 27 d, TRANS for 14 d, and FIN for 14 d. There were nine collection days (d -1 and every 7 after) in which ruminal pH was determined and nylon bags containing 5 g of diet substrates (GRW, TRANS, and FIN) were incubated in the rumen at 1200 for 48 h to determine the DM digestibility (DMD) of the three diets. Data was analyzed as a RCBD with day as a repeated measure. For the GRW diet, TRT was not different (P=0.12) for pH, but for the TRANS diet, TRT was different (P=0.02) and had a quadratic pattern (P=0.01) in which LY1 and LY3 had the greatest pH (P<0.05). For the FIN diet, TRT was also different (P=0.03), but had a linear pattern (P<0.01) in which LY2 and LY3 had greater pH than CON (P<0.05). For DMD, TRT was different (P<0.001) and had quadratic and cubic patterns (P<0.001) for the grower diet in which L2 had the lowest DMD (P> 0.05). For the TRANS diet, TRT was also different (P<0.001) and had a cubic pattern (P=0.054) in which L2 had the lowest DMD (P>0.05). For the FIN diet, TRT affected the DMD (P<0.001) and had a quadratic pattern (P<0.001) in which L2 had the lowest DMD (P>0.05). Our results indicated that the daily supplementation of 10 g of LY yielded greater DMD and ruminal pH than CON in growing cattle. [ABSTRACT FROM AUTHOR]

Direct Fed Microbials (DFM) are probiotic-type compounds that are utilized in calf feeding operations as novel, non-antibiotic technologies to improve health and performance. The modes of action of most probiotics remain unknown, but their impacts on the microbial ecology of the GI tract may be responsible for positive changes in animal health and performance. Therefore, the objective of this study was to evaluate changes in the microbiome of the ileum of Holstein steer calves supplemented with a DFM comprised of a patented strain of Bacillus subtilus (CLOSTAT®; 13 g/hd/d for 35d: Kemin Industries Des Moines, IA) following an experimental, oral Salmonella challenge. Holstein steer calves (n=40) were assigned to treatments in a 2 x 2 factorial design and either fed CLOSTAT (CLO) or not (CON) and inoculated with Salmonella Typhimurium (SAL; 1.1x 106 CFU) or not (NOSAL) in the calves' milk replacer. Our lab previously reported CLO supplementation reduced Salmonella in the GI tract and reduced the febrile response in CLO calves following SAL challenge. Upon harvest in the present study, ileum tissue samples were collected and the microflora of each calf was analyzed using Ilumina MiSeq. Diversity was examined for overall richness (OTU), quantified using the Chao 1 richness estimator, and data were examined for richness and evenness distribution amongst distinct taxa using the Shannon Diversity Index. Group differences were analyzed using permutational multivariate analysis of variance. There was no difference in the number of distinct species or genera present within the microbiome between CLO and CON or the interaction of CLO supplementation and SAL inoculation (P>0.20). Inoculation of calves with Salmonella increased species/genera richness (P=0.02) in the ileum. Overall, there was no difference in the Shannon Diversity Index due to CLO (P>0.05), but the diversity was increased with SAL inoculation (P<0.01). However, there was no interaction of CLO and SAL (P>0.05) on any measure of microbial diversity. Similarly, the number of OTU's were not affected by CLO (P>0.05); however, SAL increased the number of OTU's (P=0.02) in ileal contents. While positive effects on animal health were observed in SAL calves fed CLO, there was no overall difference in the composition of the microbiome of the ileum. However, SAL administration, as expected, significantly influenced the ileal microbiome of Holstein steer calves. More research is needed to fully elucidate the effects of CLO supplementation on the microbiome of calves in the various compartments of the GI tract. [ABSTRACT FROM AUTHOR]