Location: Agroecosystems Management Research2013 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 in Ames, Iowa, utilizes animal facilities at a university nutrition farm. Significant progress was made on Objectives 1.1a and 2.1a (The source of dietary protein will alter nutrient utilization within the pig, and consequently will affect manure composition and gaseous emissions), and Objectives 1.2 and 2.2b (The source of dietary carbohydrate will alter nutrient utilization within the pig, and consequently will affect manure composition and gaseous emissions), both falling under NP214. Details on the carbon and nitrogen utilization patterns of an important bacterial group in the intestinal tract have been completed and genomic analysis is progressing. In addition, both of these projects have been incorporated into a collaborative project with three universities relative to the impact of diet composition on the potential for pit methane production and foaming.
1. The agricultural antibiotic carbadox stimulates antibiotic resistance gene transfer from multidrug-resistant Salmonella. As a leading cause of foodborne disease, Salmonella can colonize the intestinal tract of food-producing animals (cattle and swine) and poultry. Some Salmonella isolates contain bacterial viruses (prophage) in their Deoxyribonucleic acid (DNA) that when activated can transfer genetic material from the host Salmonella strain to another Salmonella recipient strain. ARS Researchers in Ames, Iowa, demonstrated in the laboratory that multidrug-resistant Salmonella exposed to the antibiotic carbadox can produce viruses that transfer DNA, including antibiotic resistance genes, to other Salmonella isolates. Carbadox is often given to young pigs in the U.S. to stimulate growth and protect against disease-causing bacteria such as Salmonella. The demonstration that Salmonella exposed to carbadox results in transfer of DNA, including antibiotic resistance genes, raises concerns about the potential consequences due to carbadox usage in swine. This research benefits swine producers by providing information that may impact management choices and scientists who are developing ways to decrease the antibiotic resistance problem in bacteria.