Location: Forage-Animal Production Research
2008 Annual Report
NP 101, Component: 2, Problem Statements: 2A and 2C.
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.
Jones, K.L., Schulze, J.L., Strickland, J.R., Cross, D.L., Burns, P., Gilley, R.M., Bassoo, E., Hart, K.B., Thompson, Jr., D.L., King, S.S. 2008. Evaluation of a controlled-release domperidone delivery method for the treatment of fescue toxicosis in beef heifers. Prof Anim Sci. 24(4):342-348.
Aiken, G.E., Kirch, B.H., Strickland, J.R., Bush, L.P., Looper, M.L., Schrick, N.F. 2007. Hemodynamic Responses of the Caudal Artery to Toxic Tall Fescue in Beef Heifers. Journal of Animal Science. 2007. 85:2337-2345.
Mc Clanahan, L.K., Aiken, G.E., Dougherty, C.L. 2008. Case Study: Influence of Rough Hair Coats and Steroid Implants on the Performance and Physiology of Steers Grazing Endophyte-Infexted Tall Fescue in the Summer. Professional Animal Scientist. 24:269-276.
Liao, S.F., Alman, M.J., Vanzant, E.S., Miles, E.D., Harmon, D.L., Mcleod, K.R., Boling, J.A., Matthews, J.C. 2008. Basal Expression of Nucleoside Transporter mRNA Differs Among Small Intestinal Epithelia of Beef Steers and is Differentially Altered by Ruminal or Abomasal Infusion of Starch Hydrolysate. Journal of Dairy Science. 91(4):1570-84.