Metaphylactic antimicrobial effects on occurrences of antimicrobial resistance in Salmonella enterica, Escherichia coli and Enterococcus spp. measured longitudinally from feedlot arrival to harvest in high-risk beef cattle.

AIMS: Our objective was to determine how injectable antimicrobials affected populations of Salmonella enterica, Escherichia coli and Enterococcus spp. in feedlot cattle. METHODS AND RESULTS: Two arrival date blocks of high-risk crossbred beef cattle (n = 249; mean BW = 244 kg) were randomly assigned one of four antimicrobial treatments administered on day 0: sterile saline control (CON), tulathromycin (TUL), ceftiofur (CEF) or florfenicol (FLR). Faecal samples were collected on days 0, 28, 56, 112, 182 and study end (day 252 for block 1 and day 242 for block 2). Hide swabs and subiliac lymph nodes were collected the day before and the day of harvest. Samples were cultured for antimicrobial-resistant Salmonella, Escherichia coli and Enterococcus spp. The effect of treatment varied by day across all targeted bacterial populations (p ≤ 0.01) except total E. coli. Total E. coli counts were greatest on days 112, 182 and study end (p ≤ 0.01). Tulathromycin resulted in greater counts and prevalence of Salmonella from faeces than CON at study end (p ≤ 0.01). Tulathromycin and CEF yielded greater Salmonella hide prevalence and greater counts of 128ERYR E. coli at study end than CON (p ≤ 0.01). No faecal Salmonella resistant to tetracyclines or third-generation cephalosporins were detected. Ceftiofur was associated with greater counts of 8ERYR Enterococcus spp. at study end (p ≤ 0.03). By the day before harvest, antimicrobial use did not increase prevalence or counts for all other bacterial populations compared with CON (p ≥ 0.13). CONCLUSIONS: Antimicrobial resistance (AMR) in feedlot cattle is not caused solely by using a metaphylactic antimicrobial on arrival, but more likely a multitude of environmental and management factors.

Prevalence and Antimicrobial Susceptibility of Salmonella Serovars Isolated from U.S. Retail Ground Pork.

One objective of this study was to determine overall prevalence of Salmonella in ground pork from U.S. retail stores over three seasons including both case-ready and store-ground packages. Package types collected included: overwrap, chub, modified atmosphere packaging, and other (plastic or wax paper wrapped). Because package type represents different production systems and are subject to varied microbiological government regulation and testing methodologies, both USDA-FSIS and FDA Salmonella isolation protocols were performed. Another objective of the study was to determine serotypes and antimicrobial susceptibility profiles of the isolates obtained from the ground pork samples. Ground pork aliquots were subjected to real-time PCR. Recovered isolates were serotyped and minimum inhibitory concentration analysis to 15 antimicrobials was determined using microbroth dilution. Overall prevalence of Salmonella in ground pork from the 865 samples collected was 1.39%. Prevalence was not affected by package type (p = 0.29) nor grind location (case-ready vs. store-ground; p = 0.17). Season affected Salmonella prevalence (p = 0.05) with most isolates found during fall, and there was a tendency for geographic region to affect prevalence (p = 0.07). The USDA Salmonella isolation method was more effective at recovering isolates (p = 0.01) compared with the FDA methodology and yielded a kappa statistic of 0.26 as a measure of agreement. The serotypes isolated included: Infantis, 4,5,12:i:-, Brandenburg, Typhimurium var 5-, Seftenberg, and Johannesburg with only two packages containing multiple serotypes. No isolates were resistant to antibiotics commonly used to treat human Salmonella infections including extended spectrum cephalosporins or fluoroquinolones. Although the recovery of Salmonella from retail ground pork samples was rare, Salmonella Typhimurium (and its monophasic variant 4,5,12:i:-), which are among the most common serovars recovered from human infections, were recovered. Therefore, more effective strategies to further reduce or eliminate these pathogens from retail pork products are warranted.

Live Yeast and Yeast Cell Wall Supplements Enhance Immune Function and Performance in Food-Producing Livestock: A Review (†,)(‡).

More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and general animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products derived from the strain Saccharomyces cerevisiae. These products have been reported to have positive effects both directly and indirectly on the immune system and its subsequent biomarkers, thereby mitigating negative effects associated with stress and disease. These yeast-based products have also been reported to simultaneously enhance growth and performance by enhancing dry matter intake (DMI) and average daily gain (ADG) perhaps through the establishment of a healthy gastrointestinal tract. These products may be especially useful in times of potential stress such as during birth, weaning, early lactation, and during the receiving period at the feedlot. Overall, yeast supplements appear to possess the ability to improve animal health and metabolism while decreasing morbidity, thereby enhancing profitability of these animals.

Exogenous administration of lipids to steers alters aspects of the innate immune response to endotoxin challenge.

This study examined the effects of increasing energy availability from both dextrose and lipid treatments on the pro-inflammatory response to LPS in Holstein steers. Steers were randomly assigned to one of three groups: saline at 0.5 ml/kg body weight (Control) or 50% dextrose [0.5 ml/kg body weight (Dextrose) to mimic calm cattle's response to LPS] administered immediately prior to LPS (0.5 µg/kg body weight at 0 h) or continuous lipid emulsion infusion from -1 to 6 h [Intralipid 20% (Baxter, Deerfield, IL USA); 0.5 ml/kg/hr (Lipid) to mimic temperamental cattle]. Concentrations of non-esterified fatty acids (NEFA) were greater in Lipid compared with Control and Dextrose steers. A greater decrease in the change in rectal temperature, relative to baseline, was observed in response to LPS in Dextrose in comparison to control and Lipid steers. Cortisol was greater in Lipid than Dextrose and Control steers from -0.5 to 0 h, yet decreased from 0.5 to 5.5 h relative to LPS challenge. Concentrations of IL-6 were decreased in Lipid steers compared with Dextrose and Control steers, and were decreased in Dextrose compared with Control steers post-LPS challenge. These data suggest that increasing circulating NEFA using an exogenous Lipid emulsion may modulate the pro-inflammatory response in steers.

Yeast cell wall supplementation alters the metabolic responses of crossbred heifers to an endotoxin challenge.

This study examined the effect of feeding yeast cell wall (YCW) products on the metabolic responses of newly-received feedlot cattle to an endotoxin challenge. Heifers were separated into treatment groups receiving either a Control diet, YCW-A or YCW-C, and were fed for 52 d. Heifers were weighed on d 0, 14, 36, 38 and 52. On d 37 heifers were challenged i.v. with LPS [0.5 µg/kg body weight (BW)] and blood samples were collected relative to LPS challenge. Heifer BW increased from d 0 to 36 and from d 38 to 52, but was not affected by treatment. Post-LPS, glucose concentrations increased and were less in YCW-A than Control and YCW-C heifers. Pre-LPS, insulin concentrations were greater in YCW-A and YCW-C than Control heifers. Post-LPS, insulin concentrations increased with YCW-C having greater insulin than Control heifers. Pre-LPS, NEFA concentrations tended to be less in YCW-C than Control heifers. Post-LPS non-esterified fatty acids (NEFA) concentrations were less in YCW-C than Control and YCW-A heifers. Post-LPS, blood urea nitrogen (BUN) concentrations were greater in YCW-A than Control and YCW-C. These data indicate, based on NEFA and BUN data, that certain YCW products can enhance energy metabolism during an immune challenge without causing lipolysis or muscle catabolism.