Location: Livestock Issues Research2013 Annual Report
1a. Objectives (from AD-416):
The long-term objective of this project is to identify alternative management practices that could be implemented to improve the health, well-being, and overall productivity of swine and beef cattle in production environments. To identify these alternative management practices, it is essential that we enhance our knowledge base regarding the potential use of non-antibiotic alternatives to antibiotic supplementation used to promote growth and enhance feed efficiency, and alternatives to mass medication treatment with antibiotics, and that we develop a better understanding of how an animal's flightiness or arousal level may influence its health, well-being, and overall productivity. Specifically, during the next five years, we will focus on the following objectives: Objective 1: Evaluate yeast and chromium as potential non-antibiotic alternatives to subtherapeutic/growth promoting concentrations of antibiotics in swine and cattle production systems. Sub-objective 1A: Evaluate feeding yeast products alone or in combination with chromium on the health and productivity of newly weaned calves. Sub-objective 1B: Evaluate differences in overall health and fecal shedding of bacteria following a Salmonella challenge in newly weaned pigs supplemented with yeast products. Objective 2: Elucidate immunological and metabolic differences among feedlot cattle with various levels of flightiness and arousal to determine whether different management strategies could enhance growth, health, and well-being of cattle. Sub-objective 2A: Determine the influence of cattle flightiness and arousal level on the adaptive immune response to a vaccine challenge. Sub-objective 2B: Elucidate potential differences in metabolic hormones in cattle of differing levels of flightiness and arousal.
1b. Approach (from AD-416):
Our research will focus on enhancing health, performance, and overall well-being in beef cattle and swine during periods of production known to be stressful, such as weaning and transition into a feedlot. For Sub-objective 1A, an experiment will be conducted to evaluate the inclusion of yeast products and chromium in the diets of weaned beef calves as a means to prime and enhance their immune system. Blood samples will be collected for whole blood cell analysis and analysis of hormones associated with the immune and stress responses. Blood samples will also be collected to evaluate the immune cell responses to in vitro immunostimulation. Feed intake and body weights will be recorded to evaluate the potential influence of the various feed supplements on growth performance of the calves. For Sub-objective 1B, an experiment will be conducted to determine if supplementing the young pig's diet with a yeast cell wall (Saccharomyces cerevisiae) product will enhance growth performance, reduce Salmonella-induced sickness, and reduce tissue Salmonella contamination in pigs that have been orally inoculated with live Salmonella. Blood samples will be collected and analyzed for cortisol and pro-inflammatory cytokines. Tissue and fecal samples will be collected to evaluate the influence of diet on the presence or absence of Salmonella. Feed intake and body weights will be collected to evaluate the potential influence of the yeast cell wall product on pre- and post-challenge growth and performance. For Sub-objective 2A, crossbred Angus calves will be used in an experiment to determine if the level of flightiness and excitability displayed by an individual calf will influence the adaptive immune response to vaccination. Calves will be categorized as to their level of flightiness and excitability based upon an objective exit velocity and subjective pen scoring system determined at 28 days prior to and at weaning. On day 28 post-weaning, calves will be vaccinated with a novel vaccine to evaluate their primary immune response. Blood samples will be collected and analyzed for cortisol, total IgG, and vaccine-specific IgG concentrations. For Objective 2B, an experiment will be conducted to determine if the level of flightiness and excitability displayed by an individual calf will influence its metabolic response to various metabolic challenges. Calves will be categorized as to their level of flightiness and excitability based upon an objective exit velocity and subjective pen scoring system determined at 28 days prior to, and at weaning. Blood samples from calves will be collected during routine feeding, and during a period of feed restriction in which the calves will be fed at a level of 10% below their net energy for maintenance requirement. Blood samples will be analyzed for cortisol, glucose, non-esterified fatty acids (NEFA), blood urea nitrogen (BUN), insulin, hydroxybutyrate, and creatinine concentrations to evaluate the metabolic response of the calves during each feeding regimen.
3. Progress Report:
Livestock Issues Research Unit scientists conducted five studies associated with the project objectives during FY13. For Subobjective 1A, a study was conducted to evaluate the potential health and performance benefits to newborn calves whose dams were provided a yeast supplement during the last 80 days of gestation. Results from this study indicated that providing the yeast supplement did not alter any parameters associated with calf health or performance from birth to 28 days of age. Additional laboratory work is being conducted to evaluate blood parameters to determine whether or not the treatment altered any markers associated with immune function. For Subobjective 1B, two studies were conducted to evaluate feed supplements as a means to improve the overall health of weaned pigs, and to reduce fecal shedding of bacteria following a Salmonella challenge. The first study evaluated the feasibility and efficacy of supplementing weaned pigs with a lipid-producing bacteria, Rhodococcus opacus, as a means to enhance energy availability during an immune challenge. The major finding from this study was that dosing the weaned pig with R. opacus increased circulating concentrations of triglycerides that could be used as a readily available energy source during an immune challenge. A follow-up study was conducted to evaluate whether this extra energy source would be beneficial when pigs were challenge with Salmonella. These data are currently being analyzed. Data from this first portion of this study has been presented at a scientific meeting, and has been the subject of several press articles. The second study associated with this subobjective evaluated the potential benefit of providing a yeast supplement to weaned pigs prior to a Salmonella challenge. Results from this study indicated that yeast supplementation altered various physiological and immunological parameters associated with mounting an immune response to Salmonella. While pigs supplemented with the yeast had altered febrile responses, altered metabolic responses, and altered immune cells responses to the Salmonella, there were no differences found in fecal shedding of the bacteria due to yeast supplementation. Data from this study is being prepared for presentation at a scientific meeting. For Subobjective 2A, researchers were provided access to a group of calves that were exposed to a prenatal stress. These calves were used to evaluate the influence of both prenatal stress, as well as temperament on the adaptive immune response to a vaccine challenge. Samples from this study are currently being analyzed. For Subobjective 2B, researchers were allowed access to a commercial feedlot where a study was conducted to evaluate the influence of cattle temperament on the health, performance, and carcass quality of beef cattle. Results from this study indicated that flightier cattle have lighter weight carcasses with a decreased USDA yield-grade and decreased marbling at the time of harvest, and that less flighty cattle may be more susceptible to respiratory diseases in the feedlot. Data from this study has been presented at a scientific meeting, and manuscripts are currently being prepared.
1. Bacteria as an energy source? Assuring that animals maintain a high energy level is essential to keeping them healthy and productive. But energy levels can drop during periods of nutritional stress, such as during weaning, or when the animal is faced with an organism that causes disease. A collaborative study with scientists from the Livestock Issues Research Unit, Mississippi State University, the University of Nebraska, and ARS' Food and Feed Safety Research Unit in College Station revealed that dosing weaned pigs with Rhodococcus opacus, a lipid-producing bacteria, increased triglycerides that boost energy levels. This strategy has great potential for use when an animal is facing an energy-draining situation, and would result in animals with overall improved health and well-being, and thus greater benefit to the livestock producer industry.
2. Yeast supplements help pigs fight off Salmonella. Livestock producers are looking for new strategies for improving the health, productivity, and overall well-being of animals. Of particular interest is improving the animal's ability to remain healthy during stressful periods that often compromise their ability to fight off diseases. A collaborative study with scientists from the Livestock Issues Research Unit and ARS' Food and Feed Safety Research Unit in College Station was conducted to evaluate whether providing a yeast supplement to weaned pigs prior to a Salmonella challenge would result in fewer pigs becoming infected. We found that yeast supplementation did indeed improve the pigs' ability to fight off the Salmonella, but we also found that there were no differences in the levels of the bacteria passing through the animals. Yeast supplements offer one strategy for improving the response of animals to organisms that cause disease.
3. Fast or slow cattle? Previously, scientists from the Livestock Issues Research Unit, Mississippi State University, and Texas AgriLife Research revealed that high-strung or flighty cattle are immunologically and metabolically different from calmer cattle. In fact, flighty cattle use a different energy source compared with calmer cattle, even when their health is in jeopardy. To further define differences between these two classes of cattle, a collaborative study was conducted by scientists from the Livestock Issues Research Unit, the University of Nebraska, Kansas State University, and a commercial feedlot. We found that flightier cattle have lighter weight carcasses, with a decreased USDA yield-grade and decreased marbling, thus making them less valuable. Additionally, less flighty or calmer cattle may be more susceptible to respiratory diseases in the feedlot. This information will be useful to beef producers as they strive to develop strategic management practices to improve health and growth of calves coming into the feedlots, and provides clear evidence that flighty and calm cattle should be managed differently in order to maximize profitability.
Free, A.L., Duoss, H.A., Bergeron, L.V., Shields-Menard, S.A., Ward, E., Callaway, T.R., Carroll, J.A., Schmidt, T.B., Donaldson, J.R. 2012. Survival of O157:H7 and non-O157 serogroups of Escherichia coli in bovine rumen fluid and bile salts. Foodborne Pathogens and Disease. 9:1010-1014.