Location: Forage-animal Production Research2011 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
Forages provide low-cost animal feed and feedstock for bioenergy, conserve soil and water resources, and help to mitigate man’s impact on the environment. Increasing the utilization of forages through greater understanding of the animal-plant-environment interface leads to more informed decisions regarding management protocol development for capitalizing on forage’s beneficial effects to a safe and nutritious food supply, sustainability of rural communities and the environment at large. ARS animal scientists working to improve the sustainability, productivity and competitiveness of forage-based enterprises are addressing the effects of toxic endophyte (fungus)-infected tall fescue, the most abundant forage of the Transition Zone of the Eastern half of the U.S. This forage is estimated to cost forage-animal producers nearly one billion dollars annually via lost animal production and health related issues. In the past year, these scientists have completed a 2 year study examining the benefit of suppressing the emergence of tall fescue seed heads (the most toxic portion of the plant) in reducing the incidence of toxicosis (i.e., fescue toxicosis) in grazing steers. They successfully showed that application of a growth regulating herbicide to the forage, for suppressing seed head formation, improved steer weight gains and reduced the severity of the toxicosis. The data clearly demonstrate the importance of limiting grazing of seed heads. This is very exciting news in that development of management protocols using this technology will enhance stocker production in the Transition Zone, thereby improving rural community sustainability and reducing the need to use grain for red meat production. Further, ARS scientists at Lexington, KY have documented the presence of serotonin receptors in a peripheral blood vessel model of cattle and the importance of these in the expression of fescue toxicosis. It was found that cattle exhibiting fescue toxicosis had reduced vasoconstrictive activity (i.e., unable to properly regulate blood flow) via select serotonin receptors. The animal’s inability to regulate blood supply (think of this as similar to a malfunction in the cooling system of an automobile) to its peripheral tissues leads the animal to be susceptible to heat and/or cold stress. Both reduce the animal’s productive efficiency, thereby increasing the cost of production leading to reduced sustainability of operations and any subsequent benefits rural communities and the environment might have realized. A very sensitive analytical method for detecting the endophyte toxicants in both animal and plant tissues was largely completed. This analytical method offers the opportunity to specifically track the disposition of the toxicants in animal tissues to assess potential food safety concerns raised by stakeholders. Surgical implantation of rumen cannulas in 7 goats was completed. These cannulas facilitate ready access to the goat’s rumen environment allowing in depth study of how the microbes of the rumen contribute to both the animal’s health and productivity as well as nutrient utilization and excretion (the latter important to environmental sustainability).
1. A solution for baldness: toxic endophyte-infected tall fescue induces summer hair growth in grazing cattle. Heat stress is a major problem for cattle grazing toxic endophyte-infected tall fescue pastures. It is now widely accepted that compromised blood flow to the peripheral tissues, due to ergot alkaloids in toxic endophyte-infected tall fescue, in intoxicated cattle is a major contributor to increased risk of heat stress. However, these intoxicated cattle also have characteristically long rough hair coats during the summer that may exacerbate the heat stress risks. ARS animal scientists at Lexington, KY, conducted a study to determine the effects of toxic endophyte-infected tall fescue on hair growth and retention and subsequent implications for heat stress risk. They showed that the rough hair coats of cattle grazing toxic endophyte-infected tall fescue in the summer are composed of hair that is both retained from the winter hair coat and hair that is stimulated to grow to excessive lengths during the summer. In fact, a high proportion of the hair coat was surprisingly composed of hairs that emerged during increasing day lengths during the spring and early summer. Whereas, non-intoxicated cattle (short slick hair coats) or cattle that had been sheered of hair had reduced indications of heat intolerance; the rough and shaggy hair coats on cattle grazing toxic endophyte-infected tall fescue during the summer further exasperated the hyperthermia expressed by intoxicated cattle as ambient temperature and humidity increased. These data provide a potential target for intervention in the intoxication. The increased vulnerability to heat stress by cattle that graze endophyte-infected fescue during the summer may be mitigated with the development of technologies that inhibit the disruption of hair follicle activity caused by ergot alkaloids.
2. Endophyte status of tall fescue pastures differentially effects vascular function of grazing cattle. A large number of cattle graze toxic endophyte-infected tall fescue pastures prior to entering back grounding and finishing phases of the industry. A greater understanding of how ergot alkaloids (produced by toxic endophyte-infected tall fescue) affect basic physiology is necessary to improve cattle performance to post-grazing aspects of the industry. ARS animal scientists at Lexington, KY, using blood vessels biopsied from grazing cattle, demonstrated that cattle grazing toxic endophyte-infected fescue are less able to respond to external vascular stimuli (i.e., loss of appropriate blood flow control). Further, they clearly demonstrated the presence of serotonergic receptors in the peripheral blood vessel model (lateral saphenous) and the functional linkage of these receptors with ergot alkaloid-induced peripheral vasoconstriction in cattle. The data provided some of the first information characterizing which receptors (think of these as light switches that when bound by something either turn on or turn off a cellular function) are bound by the ergot alkaloids to alter blood flow through the periphery of the animal (needed for nutrient delivery and heat dissipation). The data provided potential targets for treating the toxicosis (estimated to cost producers nearly one billion dollars annually) induced by the ergot alkaloids. Additionally, the data provided additional information to aid producers in managing back grounding and feedlot operations through an understanding of additional measures that may need to be taken to prevent illness (e.g., heat stress) in these animals already stressed via the intoxication.
3. A novel endophyte-infected tall fescue developed for the upper transition zone improves pasture and steer productivity. Ergot alkaloids, produced by an endophyte (Neotyphodium coenophialum) which infects most tall fescue and imparts tolerances to the plant to environmental stresses, are causal agents of “fescue toxicosis” in cattle. Fescue toxicosis substantially reduces animal production and well being and costs producers nearly one billion dollars annually. ARS animals scientists at Lexington, KY, partnered with University of Kentucky researchers evaluated a late maturing tall fescue genotype (KYFA9301), bred to improve seedling vigor and adapted to the northern half (upper) of the transition zone of the Eastern half of the U.S. A 2 year grazing study measured steer performance on and forage quality and productivity of the KYFA9301 tall fescue variety infected with the AR584 novel endophyte (AgResearch Ltd.) which produces no ergot alkaloids but does provide environmental tolerance to the plant. The widely used toxic endophyte-infected Kentucky 31 tall fescue, and the nontoxic MaxQ and endophyte-free KYFA9301 tall fescue varieties were included for comparisons. Results indicated that the novel endophyte-infected KYFA9301 improved weight gain and alleviated fescue toxicosis, and can provide higher pasture carrying capacities than MaxQ in the late spring and early summer. This novel endophyte-infected variety will soon be commercially available to producers. It is the first novel endophyte-infected tall fescue specifically developed/adapted to the northern part of the transition zone and will expand production opportunities via stand longevity, forage quality and improved stocking rates. Ultimately, the new variety is expected to improve sustainability of forage-based enterprises and attendant benefits to rural communities and the environment offered by forage.
4. Use of a natural product, plantain, and urea to improve forage silages in an african country, Ghana. Silage additives have been developed to improve fermentation and nutritive value. It is possible to use natural products to promote adequate fermentation patterns, especially under sub-optimal conditions. ARS animal scientists at Lexington, KY, conducted a study, in collaboration with scientists at the Council for Scientific and Industrial Research in Ghana, Africa, to evaluate the effect of urea and plantain as additives on silage produced with late-cut bermudagrass and switchgrass silages (similar low quality forages found in Ghana), and the effect of increasing percentages of alfalfa in mixture with bermudagrass or switchgrass on silage quality. Additions of plantain, plantain and urea, and alfalfa to late-cut grasses improved fermentation characteristics and silage quality when moisture percentage of the grass was about 60%. Silage additives were identified that can reduce the risk to farmers in tropical and sub-Saharan Africa in making silage from mature tropical grasses that are needed to feed livestock during annual dry seasons.
5. Ergopeptines alter cattle brain cell function. Ergopeptines, produced by an endophyte (Neotyphodium coenophialum) which infects most tall fescue are causal agents of “fescue toxicosis” in cattle. Fescue toxicosis substantially reduces animal production and well being and costs producers nearly one billion dollars annually. Besides their effects on the dopamine-like-2 receptor, little is known about which cellular proteins interact with these toxic ergopeptines. In collaboration via a Specific Cooperative Agreement, University of Kentucky and ARS scientists at Lexington, KY, used synaptic vesicles isolated from bovine cerebral cortical tissue, to analyze the ability of ergovaline, ergotamine and ergocornine to inhibit vesicular glutamate transporter (VGLUT; important in support of normal brain functions) activity. They showed that these 3 ergopeptines inhibit VGLUT activity with differing inhibitory affinities (ergotamine > ergocornine > ergovaline; ergotamine the most potent inhibitor). These results demonstrate that the function of glutamatergic neurons in cattle consuming endophyte-infected tall fescue likely is compromised and suggest that the function of VGLUT in other cell types also may be compromised. Compromising VGLUT activity has implications in nitrogen metabolism and brain function, both of which impact animal performance and health.
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