Location: Forage-animal Production Research2008 Annual Report
1a. Objectives (from AD-416)
The long-term goal of this project is to improve competitiveness and sustainability of forage-based animal enterprises in the transition zone between the subtropical south and temperate north of the eastern half of the United States. Over the next 5 years the Forage-Animal Production Research Unit (FAPRU) and collaborators will focus on the following objectives: Objective 1: Improve forage-animal health, performance, and forage intake and utilization. Subobjective 1.A. Develop and validate analytical methodologies for profiling ergot alkaloids produced by toxic endophyte-infected (TE) tall fescue (TF), and resulting metabolites following consumption and metabolism by animals. Subobjective 1.B. Identify the biotic components and mechanisms of the animal-plant interface impacting grazing animal health and production. Subobjective 1.C. Enhance nutrient utilization through an improved understanding and manipulation of microorganisms of the rumen. Objective 2: Improve animal and forage productivity of forage-based systems through optimization of grazing and preconditioning management protocols. Subobjective 2.A. Evaluate animal performance on novel endophyte-infected TF pastures. Subobjective 2.B. Develop a preconditioning program to reduce morbidity and mortality in feeder calves that have been backgrounded on TE TF.
1b. Approach (from AD-416)
Forage systems provide low-cost feed, conserve soil and water resources, and mitigate man’s impact on the environment. However, basic biological information is limited on how plant metabolites affect animal performance and health beyond the production level. Fundamental information concerning how these production level effects are elicited has only recently become a focus. As such, the available information for predicting animal performance in response to plant nutrients under varying environmental, genetic, physiological status, and management conditions is of limited use. Even more problematic is the poor understanding of the effects of plant nutraceuticals and anti-quality factors on nutrient intake, metabolism and assimilation for product, health maintenance, or work by the animal. To increase the sustainability of forage-based enterprises, it is essential that a better understanding be developed of the fundamental biological processes underlying the interactions between the animal, plant, and environment. This project, through the development and utilization of cutting-edge technologies and real world testing, proposes to decipher the complex interactions within the animal-plant interface in order to accomplish the following two objectives: 1) improve forage-animal health, performance, and forage intake and utilization; and 2) improve animal and forage productivity of forage-based systems through optimization of grazing and preconditioning management protocols. These objectives will be focused on the predominant forage (tall fescue) of the transition zone and its alternatives. Accomplishing these objectives will improve sustainability of forage-based enterprises through more reliable predictions on the impacts of management and environment on animal health and performance.
3. Progress Report
Research conducted under this project enhances animal well-being in livestock production systems and improves efficiency of nutrient utilization and conversion to animal products and addresses National Program (NP) 101, Food Animal Production, Action Plan Component 2, “Enhancing Animal Adaptation, Well-Being and Efficiency in Diverse Production Systems. Specifically, this research addresses Problem Statement 2.A (Enhance Animal Well-Being and Reduce Stress in Livestock and Poultry Production Systems) and Problem Statement 2.C (Improving Efficiency of Nutrient Utilization and Conversion to Animal Products). Further, a high level of cooperation is required between this NP 101 project and the companion NP 215 project (6440-21000-001-00D) at the Forage-Animal Production Research Unit. Specific progress this cycle includes: Analyzed ergot alkaloid levels of several vascular beds collected from cattle grazing endophyte-infected tall fescue; analyzed ergot alkaloid levels of cattle lateral saphenous vein segments exposed to varying alkaloid concentrations in vitro; developed an isolated cattle right ruminal vein bioassay; determined that both cattle ruminal vein and artery contractile response to serotonin was greater than norepinephrine in vitro and that both vessels had distinct contractile responses to serotonin and norepinephrine, but identical responses to KCl; pharmacologically determined the presence of serotonin receptors 5HT1B, 2A, and 5HT7 on cattle lateral saphenous veins but 5HT2B was not present; determined that 5HT2A and 5HT7 agonist-induced responses in cattle lateral saphenous veins were affected by prior exposure to grazing tall fescue; completed the microarray analysis of saphenous vein cDNA collected from steers grazing high- and low-endophyte infected pastures and preparations are in progress to confirm detected changes in gene expression with real-time PCR; isolated ammonia producing bacteria from forage-fed meat goats using casein hydrolysates and corn gluten hydrolysate and efforts are in progress to determine if the isolates are similar; hops extracts are currently being evaluated as a model dietary treatment product to inhibit the growth of the three well-studied ammonia producing rumen bacteria in vitro; identified and characterized cellobiose utilizing bacteria from cattle on low and high endophyte infected tall fescue diets; collected year two of data of the effects of soybean hull feeding and/or steroidal implantation on cattle tolerance to toxic endophyte-infected tall fescue with indications that feeding soybean hulls or using steroidal implants in the cattle on pasture have improved weight gains and hair coat shedding. NP 101, Component: 2, Problem Statements: 2A and 2C.
1. Hemodynamics in the caudal artery of beef heifers fed different ergot alkaloid concentrations. Fescue toxicosis, induced by ergot alkaloids (e.g., ergovaline) produced in endophyte-infected tall fescue, is a syndrome that costs cattle, horse, and small ruminant producers nearly a billion dollars a year in lost production. Although the syndrome was identified approximately 30 years ago, the lack of sensitive tools for measuring in vivo (real time) effects of the intoxication have hindered our ability to define the threshold level of exposure for induction of fescue toxicosis and also, the development of fully successful mitigation protocols for the syndrome. Recently, FAPRU scientists have validated the use of Doppler ultrasonography for tracking fescue toxicosis induced vascular dysfunction (a primary functional deficit in intoxicated animals) in cattle on endophyte-infected tall fescue. Using Doppler ultrasound technology, determined that caudal artery area and blood flow rates were reduced in heifers receiving endophyte-infected tall fescue seed and that these reductions were related to dose and length of exposure. These data demonstrate the usefulness of Doppler ultrasound technology as a tool for the real time study of fescue toxicosis and form the beginnings of a database that will be useful in determining the threshold level of intoxication. NP 101, Component: 2, Problem Statements: 2A and 2C.
2. Kinetic characterization of how bromocryptine (a model ergopeptine alkaloid) inhibits uptake of uridine by polarized bovine epithelia. In ruminants, microbial-derived nucleic acids are a major source of N and are absorbed as nucleosides by small intestinal epithelia and reabsorbed by renal epithelia. Although the biochemical activities of 2 nucleoside transport systems have been described for cattle, nothing is known about their sensitivity to ergot alkaloids (apparent causative agents of fescue toxicosis). Using an in vitro bovine epithelial cell culture model (Madin-Darby Bovine Kidney [MdBK] cells), delineated the sensitivity of the ENT2 equilibrative nucleoside transporter to inhibition of uridine uptake by bromocryptine; demonstrated that the IC50 curve for inhibition of uridine uptake by ENT2-activity was essentially identical to that observed for ergovaline (alkaloid of endophyte-infected tall fescue and suspect causative agent of fescue toxicosis); identified the mode of bromocrytpine inhibition of uridine uptake by ENT2 as a “mixed” mode of inhibition, suggesting that ergopeptines inhibit through both competition with uridine for binding and an allosteric mechanism; documented that D2 receptor protein is expressed by MDBK cells and highly sensitive to forskolin-stimulated production of cAMP. Enhancement of current prediction models and future improvements in the efficiency of nitrogen utilization in beef cattle. NP 101, Component: 2, Problem Statements: 2A and 2C.
3. Influence of ruminal and post-ruminal starch digestion on basal expression of nucleoside transporter mRNA in beef steers consuming forage. In ruminants, microbial-derived nucleic acids are a major source of N and are absorbed as nucleosides by small intestinal epithelia. Although the biochemical activities of 2 nucleoside transport systems have been described for cattle, little is known regarding the regulation of their gene expression. Demonstrated (in vivo) the differential expression of concentrative and equilibrative nucleoside transporters within the various segments of the small intestine and a positive relationship between expression of nucleoside transporters within the small intestine and luminal supply of nucleosides and glucose. Enhancement of current prediction models and future improvements in the efficiency of nitrogen utilization in beef cattle. NP 101, Component: 2, Problem Statements: 2C.
4. Determination that protein expression of two amino acid metabolizing enzymes is increased in the livers of steers grazing endophyte-infected tall fescue (ergot alkaloid containing) pasture. The health and production of cattle grazing endophyte-infected tall fescue containing ergot alkaloids is impaired, resulting in large economic losses to producers (nearly one billion dollars per year). However, little is known about the effects of endophyte-infected tall fescue on the expression of enzymes and transporter proteins by the liver, kidney, or skeletal muscle tissues. An in vivo study was conducted that evaluated the potential effect of endophyte exposure on the expression of 5 enzymes and 3 transporter proteins critical for whole-body carbon and nitrogen balance in steers that had grazed endophyte-infected tall fescue for a whole summer vs steers grazing a non-endophyte infected pasture. Determined that two liver enzymes (aspartate transaminase and phosphopenolpyruvate carboxykinase) involved with the conversion of amino acids into the precursors for glucose were increased in steers consuming endophyte-infected tall fescue pasture. In contrast, kidney and skeletal muscle expression of any protein was not affected. Enhance current prediction models and facilitate development of metabolic indices to determine how long cattle can consume endophyte-infected tall fescue before impaired metabolic function occurs. NP 101, Component: 2, Problem Statements: 2A and 2C.
5. Effects of Plateau and Cimarron on broodmares. Mares grazing endophyte-infected tall fescue frequently incur reproductive problems including prolonged gestation, dystocia and agalactia. These deleterious effects can result in death of the mare/and or foal. Plateau and Cimarron are herbicides known to kill tall fescue without significantly harming desirable pasture grasses, but potential detrimental effects on pregnant mares was not known. In four experiments conducted over two years a total of 60 pregnant mares were allowed to graze pastures treated with Plateau, Cimarron, or vehicle carriers. Pregnancies were monitored by palpation and ultrasonography. Determined that the two tested herbicides had no effects on mare blood chemistry, hematology or foaling rates. Provides a solution for horse farm managers to safely utilize herbicides for control of endophyte-infected tall fescue to avoid costly reproductive problems associated with fescue toxicosis. Note: this research was conducted at the direct request of horse farm producers. NP 101, Component: 2, Problem Statement: 2A.
5. Significant Activities that Support Special Target Populations
Conducting a research project with University of Kentucky and Berea College faculty aimed at understanding the effects of tall fescue (especially endophyte-infected) on meat goat production. This project is not only providing much needed data for the meat goat industry, a rapidly growing industry well suited to small acreage farms, but is also providing a learning opportunity for a number of first generation college students from the Appalachian region of eastern Kentucky. Conducting a research project with Kentucky State University faculty on the microbial ecology of the goat rumen. This project will not only provide much needed data for meat goat production, a growing industry suited to small farms and culturally important to Arabic-, African-, and Mexican-Americans but provides unique education opportunities at a traditionally minority-serving institution. A collaboration continues with the Kentucky and Iowa Cooperative Extension Services, whereby approximately 300 beef calves are ultrasonically scanned from various small farms in Kentucky to measure ribeye area and backfat over the 12th to 13th ribs, and rump fat prior to transport to the feedyard. All feeder calves are rescanned at the approximate midpoint of their residences times in the feedyard. The project is providing information to producers on feedyard efficiency and carcass traits, which can be used in making management decisions on management and herd genetics. Additionally, work is beginning that is developing models for estimating intramuscular fat (i.e., marbling) using higher resolution ultrasound units that should improve reliability of estimates over those derived from lower resolution units that are presently being used. A workshop was organized with the Kentucky Cooperative Extension Service that presented updated information on the establishment and management of eastern gamagrass, a warm-season perennial grass that has gained popularity among cattle producers and wild life managers. There were approximately 70 producers and extension agents that attended the workshop held at the Anderson County Extension office on August 10, 2007. One FAPRU Animal Scientist was interviewed for an article in The Horse Magazine (May, 2008), entitled Eradicating Erosion: Ways to Protect your Pasture. The information provided was on grazing management to minimize soil erosion. In June 2006 an Animal Research Center Field Day was held to highlight research conducted with livestock and forage management presented by University of Kentucky and USDA-ARS FAPRU scientists. Approximately 200 farmers, county agents, and industry personnel from 36 counties and four states attended. Field day tours included beef cattle nutrition research, beef and sheep grazing, and optimizing forage management.
Klotz, J.L., Kirch, B.H., Aiken, G.E., Bush, L.P., Strickland, J.R. 2008. Effects of Selected Combinations of Tall Fescue Alkaloids on the Vasoconstrictive Capacity of Fescue-Naive Bovine Lateral Saphenous Veins. Journal of Animal Science. 2008. 86:1021-1028.