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

"Preharvest" Food Safety for Escherichia coli O157 and Other Pathogenic Shiga Toxin-Producing Strains

Preharvest food safety refers to the concept of reducing the rates of contamination of unprocessed foods with food-borne disease pathogens in order to reduce human exposure and disease. This article addresses the search for effective preharvest food safety practices for application to live cattle to reduce both contamination of foods of bovine origin and environmental contamination resulting from cattle. Although this research has resulted in several practices that significantly decrease contamination by Escherichia coli O157, the effects are limited in magnitude and unlikely to affect the incidence of human disease without much wider application and considerably higher efficacy than is presently apparent. Infection of cattle with E. coli O157 is transient and seasonally variable, likely resulting from a complex web of exposures. It is likely that better identification of the true maintenance reservoir of this agent and related Shiga toxin-producing E. coli is required to develop more effective control measures for these important food- and waterborne disease agents.

Food-producing animals and their health in relation to human health

The fields of immunology, microbiology, and nutrition converge in an astonishing way. Dietary ingredients have a profound effect on the composition of the gut microflora, which in turn regulates the physiology of metazoans. As such, nutritional components of the diet are of critical importance not only for meeting the nutrient requirements of the host, but also for the microbiome. During their coevolution, bacterial microbiota has established multiple mechanisms to influence the eukaryotic host, generally in a beneficial fashion. The microbiome encrypts a variety of metabolic functions that complements the physiology of their hosts. Over a century ago Eli Metchnikoff proposed the revolutionary idea to consume viable bacteria to promote health by modulating the intestinal microflora. The idea is more applicable now than ever, since bacterial antimicrobial resistance has become a serious worldwide problem both in medical and agricultural fields. The impending ban of antibiotics in animal feed due to the current concern over the spread of antibiotic resistance genes makes a compelling case for the development of alternative prophylactics. Nutritional approaches to counteract the debilitating effects of stress and infection may provide producers with useful alternatives to antibiotics. Improving the disease resistance of animals grown without antibiotics will benefit the animals’ health, welfare, and production efficiency, and is also a key strategy in the effort to improve the microbiological safe status of animal-derived food products (e.g. by poultry, rabbits, ruminants, or pigs). This review presents some of the alternatives currently used in food-producing animals to influence their health in relation to human health.

Evaluation of a shelf-stable direct-fed microbial for control of Escherichia coli O157 in commercial feedlot cattle

Stanford, K, Gibb, D. and McAllister, T. A. 2013. Evaluation of a shelf-stable direct-fed microbial for control of Escherichia coli O157 in commercial feedlot cattle. Can. J. Anim. Sci. 93: 535–542. A direct-fed microbial (DFM) registered for use in cattle in Canada containing Lactobacillus acidophilus strain BT-1386 and a Saccharomyces cerevisiae yeast autolysate was evaluated for control of E. coli O157. Weaned calves entered the feedlot in October and November and in January were sorted into Control (12 pens with a total of 2170 calves) and DFM treatment groups (10 pens with a total of 2040 calves). Although targeted dosage of L. acidophilus was 9 log10 colony forming units (CFU) head−1 d−1, analyses after storage at ambient temperature showed an average dose of 8.6 Log10 CFU head−1 d−1 and demonstrated stability of DFM over the range of temperatures encountered (−32.6 to 32.9°C) during storage. Calves entering the feedlot had low prevalence (0.8%) of E. coli O157 in feces, which increased to 11.2% in January. A 47°C range in ambient temperature for that month may have stressed cattle and led to increased shedding of E. coli O157 compared with seasonal norms. Comparing hide swabs collected at initiation of DFM feeding with those at shipping for slaughter, prevalence of E. coli O157 declined (P<0.05) in cattle fed DFM, although prevalence of E. coli O157 in hide swabs from Control and DFM-treated cattle did not differ at any time. As well, numbers of E. coli O157 and prevalence of the organism in fecal pats did not differ among treatments. Colonization of calves with E. coli O157 prior to DFM feeding likely reduced efficacy of DFM in the present study. Additional information regarding timing of feeding DFM relative to interactions among organisms within the gastrointestinal tract of cattle are required to ensure consistent efficacy of DFM for pre-harvest control of E. coli O157.

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.