David J. Nisbet

Bio: David J. Nisbet is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Salmonella & Population. The author has an hindex of 57, co-authored 377 publications receiving 11080 citations. Previous affiliations of David J. Nisbet include Agriculture and Agri-Food Canada & Agricultural Research Service.

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.

Abstract: 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 = 007) in the 25 and 50% DDG diets compared with controls Ruminal pH was decreased (P < 005) 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

Diet, Escherichia coli O157:H7, and cattle: a review after 10 years.

Abstract: Escherichia coli are commensal bacteria that can account for up to 1% of the bacterial population of the gut. Ruminant animals are reservoirs of the pathogenic bacteria E. colil strain O157:H7, and approximately 30% of feedlot cattle shed E. coli O157:H7. Feedlot and high-producing dairy cattle are fed high grain rations in order to increase feed efficiency. When cattle are fed high grain rations, some starch escapes ruminal microbial degradation and passes to the hindgut where it undergoes fermentation. Ten years ago researchers demonstrated that populations of total E. coli were higher in grain-fed than in forage-fed cattle, and when cattle were abruptly switched from a high grain diet to an all hay diet, total E. coli populations declined 1000-fold within 5 days and reduced the ability of the surviving E. coli to survive an acid shock mimicking passage through the human gastric stomach. This research provoked many questions about the effects of diet or E. coli O157:H7 populations that have not been conclusively answered to date. Subsequent research has shown that diet does affect E. coli O157:H7 populations, but the effects have varied in magnitude and impact. Further studies have demonstrated that the effects of forage feeding on E. coli O157:H7 populations may be due to concentrations of tannins and phenolic acids in forages. Other ration components such as rapidly ruminally fermented grains (e.g., barley) increase the shedding of E. coli O157:H7, and in some situations, feeding distillers grains can increase fecal shedding of E. coli O157:H7 due to VFA concentrations. Data from researchers across North America indicate that diet does impact STEC/EHEC populations in cattle prior to slaughter; however the economic, logistic and practical impacts of dietary changes must be examined and accounted for.

Probiotics, prebiotics and competitive exclusion for prophylaxis against bacterial disease.

Abstract: 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.

Foodborne Campylobacter: Infections, Metabolism, Pathogenesis and Reservoirs

Abstract: Campylobacter species are a leading cause of bacterial-derived foodborne illnesses worldwide. The emergence of this bacterial group as a significant causative agent of human disease and their propensity to carry antibiotic resistance elements that allows them to resist antibacterial therapy make them a serious public health threat. Campylobacter jejuni and Campylobacter coli are considered to be the most important enteropathogens of this genus and their ability to colonize and survive in a wide variety of animal species and habitats make them extremely difficult to control. This article reviews the historical and emerging importance of this bacterial group and addresses aspects of the human infections they cause, their metabolism and pathogenesis, and their natural reservoirs in order to address the need for appropriate food safety regulations and interventions.

Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics

Abstract: With the continued interest in the role of the gut microbiota in health, attention has now turned to how to harness the microbiota for the benefit of the host. This Consensus Statement outlines the definition and scope of the term 'prebiotic' as determined by an expert panel convened by the International Scientific Association for Probiotics and Prebiotics in December 2016. In December 2016, a panel of experts in microbiology, nutrition and clinical research was convened by the International Scientific Association for Probiotics and Prebiotics to review the definition and scope of prebiotics. Consistent with the original embodiment of prebiotics, but aware of the latest scientific and clinical developments, the panel updated the definition of a prebiotic: a substrate that is selectively utilized by host microorganisms conferring a health benefit. This definition expands the concept of prebiotics to possibly include non-carbohydrate substances, applications to body sites other than the gastrointestinal tract, and diverse categories other than food. The requirement for selective microbiota-mediated mechanisms was retained. Beneficial health effects must be documented for a substance to be considered a prebiotic. The consensus definition applies also to prebiotics for use by animals, in which microbiota-focused strategies to maintain health and prevent disease is as relevant as for humans. Ultimately, the goal of this Consensus Statement is to engender appropriate use of the term 'prebiotic' by relevant stakeholders so that consistency and clarity can be achieved in research reports, product marketing and regulatory oversight of the category. To this end, we have reviewed several aspects of prebiotic science including its development, health benefits and legislation.

Diseases of Poultry

Abstract: VERY few veterinary surgeons have thought fit to write a book on diseases of poultry. Mr. Ernest Gray has done justice to the subject and is to be congratulated on his effort. A book of this size, written by one with specialized knowledge, will add to the value of any library or private bookshelf. Diseases of Poultry Their Aetiology, Diagnosis, Treatment and Control; with a Section on the Normal Anatomy and Physiology of the Fowl. By Ernest Gray. (Lockwood's Agricultural and Horticultural Handbooks.) Pp. x + 198 + 16 plates. (London: Crosby Lockwood and Son, Ltd., 1940.) 9s. 6d. net.