Location: Agroecosystems Management Research2012 Annual Report
1a. Objectives (from AD-416):
The goal of the project is to develop a comprehensive understanding of the interrelationships between nutrient inputs in livestock production systems, as derived from agricultural and industrial byproducts, and the impact on nutrient utilization, animal health, gastrointestinal ecology, and pathogen shedding in an effort to minimize environmental impact, accomplished through the four interlinked objectives as outlined and depicted below: 1. Manipulate swine dietary ingredients to improve nutrient utilization and reduce nutrient excretion and the emission of gasses into the environment. 2. Quantify and modify swine gastrointestinal microflora to improve nutrient utilization and reduce the emission of gasses into the environment. 3. Quantify the impact of swine dietary regimens on nutrient metabolism and immune function of the gastrointestinal tract and the whole animal in order to assess the potential tradeoffs between environmental concerns and production. 4. Exploit genetically-mediated mechanisms involved in Salmonella colonization of the swine gastrointestinal tract to reduce subsequent shedding into manure.
1b. Approach (from AD-416):
The impact of dietary ingredients on nutrient utilization in the pig and subsequent nutrient excretion and emission of gasses into the environment will be assessed through altering the source and level of dietary protein and carbohydrate. The protein level will be adjusted relative to the level of soybean meal and amino acid supplementation utilized in diet formulation, while the protein source factor will be accomplished by replacing soybean meal with either canola meal, corn gluten meal, or poultry meal. The source and level of complex carbohydrate will be accomplished by utilizing barley, beet pulp, distillers dried grains with solubles, soybean hulls, and wheat bran as a partial replacement of soybean meal. Nutrient retention, excretion, and gas emissions will be accomplished using animal metabolism trials and the employment of a manure storage system currently in place at the lab. Microbial ecology of the large intestine (via fresh feces) and manure, as affected by the source and level of protein and carbohydrate, will be assessed by classical and molecular methods currently employed at the Unit, using the same pigs and diets as described above. The impact of dietary regimens on nutrient metabolism and immune function will be accomplished by utilizing similarly formulated diets as above, but on a separate group of pigs, with assessment of systemic and intestinal immune system function using techniques currently being utilized within the Unit. Lastly, reduction of Salmonella colonization of the swine gastrointestinal tract for subsequent reduction of shedding into the environment will be accomplished by administration of a chemical compound to disrupt pathogen sensing, vaccination using an attenuated S. Typhimurium strain, and manipulation of crude protein levels in the diet (as described above).
3. Progress Report:
The ARS Unit utilizes animal facilities at the Iowa State University Swine Nutrition Farm. Significant progress was made on Objective 1.1a, 2.1, and 3.1a, largely due to access to pigs and facilities allowing the initiation of the research project evaluating the impact of dietary crude protein on manure composition and air quality, all falling under NP214. Also due to increased pig and facility access, significant progress has been made in scheduling activities associated with Objectives 1.2 and 2.2, whereupon the research project dealing with the impact of dietary fiber on manure composition and air quality has been moved forward on the research calendar. Significant progress on Objectives 4.1 and 4.1 was also achieved, which falls under NP214. As the leading cause of bacterial foodborne disease and death in the U.S., Salmonella can frequently colonize the gastrointestinal tracts of food-producing animals. Interventions are needed to reduce the on-farm incidence of Salmonella colonization in swine to improve animal health and enhance food safety. A rationally attenuated Salmonella enterica serovar Typhimurium vaccine was designed and tested in swine to determine if vaccination with the attenuated Salmonella strain could protect against challenge with a virulent, wild-type Salmonella Typhimurium strain.
1. The use of a covariate reduces experimental error in nutrient digestion studies in growing pigs. Variation is inevitable in animal research with experiments evaluating body composition and meat quality often utilizing covariates (a mathematical procedure to account for biological differences among animals) in data analysis. In general, nutrition studies do not utilize covariates, but instead utilize blocking relative to initial body weight or previous treatment. Based on data obtained in this experiment, ARS researchers in Ames, Iowa, determined that initial digestibility coefficients are an effective method in reducing the variation associated with subsequently obtained data, and should be considered as a covariate in future grow-finish swine digestibility research. This research is currently providing nutritionists a valuable model from which to minimize experimental variation and improve the ability to detect treatment differences and minimize the number of animals needed to obtain significant treatment differences.
3. Intestinal bacteria functionally similar among mammal hosts. The large intestine in mammals contains trillions of microbes, many of which are capable of utilization of feeds with high fiber content. Bacteriodes is a major component of this microbial community. There is a need to study these microorganisms as they can contribute significantly to the host’s nutrient status. ARS researchers in Ames, Iowa, isolated over 2,000 bacteria with 400 belonging to the Bacteroides ovatus, B. thetaiotaomicron, and B. xylanisolvens group from cow, goat, pig, and human feces. These Bacteriodes isolates were tested for their ability to use a range of carbohydrates, amino acids, and other nutrients. Patterns of nutrient utilization by Bacteriodes were not specific to a particular host. It appears that the specific function of these three bacterial species is similar in all four of the host mammals. This data will be used by scientists and others studying the interaction of the host and its microbiome, as it suggests that some of the functionality of the large intestine is similar across mammals; in particular, utilization of fiber. The results of this research will be used to improve feed utilization in pigs by tapping into the power of the microbes, thus reducing nutrient excretion in the urine and feces. Additionally, due to the similarities in the bacterial species isolated and lack of specific traits associated with host origin, pigs can be used as a model to study the intestinal microbiology of all mammals and allow for sampling beyond just feces.
3. Commercially available enzymes, yeast, or probiotics have little effect on nutrient digestibility in nursery and finishing pigs. ARS researchers in Ames, Iowa, determined that because pigs are only able to utilize moderate levels of fiber, there is a need to increase digestion of structural carbohydrates, especially in corn-derived co-products. Use of feed additives (enzymes, yeast, and probiotics) to improve the nutritional value of corn co-products, particularly dried distillers grains with solubles which are relatively high in fiber, would be of great value to the swine industry. This data is providing the swine industry information indicating that feed additives have minor effects on nutrient digestibility and pig growth performance when fed nutritionally-adequate, corn-soy diets containing 30% dried distillers grains with solubles, and are, therefore, not economically advantageous.
Dozier,III, W.A., Kerr, B.J., Branton, S.L. 2011. Apparent metabolizable energy of crude glycerin originating from different sources in broiler chickens. Poultry Science. 90:2528-2534.