Location: Forage-animal Production Research2012 Annual Report
1a. Objectives (from AD-416):
The long-term goal of this project is to improve competitiveness and sustainability of forage-based enterprises in the transition zone of the Eastern half of the United States of America. Over the next five years we will focus on the following objectives as determined by stakeholder input and ARS National Program 215 (Rangeland, Pastures and Forages) approval. Objective 1. Improve persistence, productivity, and quality of forage grasses and legumes for use in the transition zone of the Eastern and Midwestern U.S. Subobjective 1.A. Determine relative interactions between tall fescue (TF) and endophytes involved in regulating plant growth, forage quality, and persistence under a variety of environmental conditions. Subobjective 1.B. Identify, characterize, and manipulate useful traits (chemical, physical, genetic) to develop forages that are: biologically diverse, tolerant of biotic and abiotic stresses, competitive, high quality for animal production, persistent, and easy to establish and maintain. Objective 2. Improve animal and forage productivity on forage-based systems through optimal combinations of forages, supplementation and grazing systems tailored to animal needs and environmental conditions. Subobjective 2.A. Evaluate forage production characteristics relevant to plant and animal performance on pastures containing new novel endophyte-infected (EI) TFs. Subobjective 2.B. Develop a forage system for the upper transition zone that utilizes warm season perennial grasses to improve animal performance and profitability. Subobjective 2.C. Identify the abiotic/biotic components and mechanisms of the plant-animal-environment interface impacting pasture production and environmental quality factors.
1b. Approach (from AD-416):
Forage systems provide low-cost feed, conserve soil and water resources, and mitigate man’s impact on the environment. Limited basic biological information exists on how plant and/or fungal metabolites affect forage plant quality, persistence, and production. Even less information exists on the cross-talk mechanism between tall fescue (the predominant forage of the transition zone) and its endophyte. Furthermore, little is known about the impact that forage and/or fungal metabolites have on their pasture ecosystems. Gaps in our current knowledge are hindering researchers’ abilities to predict and select best combinations of forages and management systems for use by various forage-animal production enterprises. Aiding researchers to develop new forage varieties, forage systems, and management recommendations will require an improved understanding of both metabolite (plant and fungal) profiles and their biological functions at the molecular and organismal levels. Such understanding of metabolites, molecular mechanisms, and whole-organism responses, and of their impact on plant quality, persistence, and production, is necessary for improving sustainability of forage-based enterprises. This Project Plan, through the development and utilization of cutting-edge technologies and real-world testing, proposes to decipher the complex interactions within the animal-plant-environment interface. In order to accomplish this task and improve sustainability of forage-based enterprises, the following two objectives are proposed: 1) Improve persistence, productivity, and quality of forage grasses and legumes for use in the transition zone of the Eastern and Midwestern United States; and 2) Improve animal and forage productivity on forage-based systems through optimal combinations of forages, supplementation, and grazing systems tailored to animal needs and environmental conditions. These objectives are focused on the predominant forage of the transition zone, tall fescue, as well as on its alternatives and companion species. Accomplishing these objectives will improve sustainability of forage-based enterprises through improved forages, forage management and systems, and basic understanding of the plant/fungal metabolite effects on forage plant persistence and production, as well as consequent effects on the structure and function of pasture ecosystems.
3. Progress Report:
Project scientists conducted ribonucleic acid (RNA)-seq experiments as well as metabolite analysis on endophyte-infected (E+) and endophyte-free (E-) tall fescue (Lolium arundinaceum) clone pairs toward gaining insight into the cross-talk mechanisms between tall fescue and its endophyte (Neotyphodium [N] coenophialum) during drought induced stress. Data analysis is currently underway and initial results are indicating significant RNA expression and metabolite profile differences between E- and E+ tall fescue under drought stress and during recovery. Project scientists demonstrated that crude red clover extracts and biochanin A are inhibitory of Clostridium sticklandii, a bovine hyper ammonia producing bacterium, which degrades amino acids in the rumen, suggesting that red clover extract has the potential to improve protein assimilation in ruminants, thereby increasing feed efficiency while potentially decreasing waste nitrogen to the environment. More than 300 red clover genes were mapped to known location in the Medicago trucatuala genome revealing broad regions of conservation and also identified numerous chromosomal rearrangements between the two genomes. These scientist are continuing their work toward alignment of the red clover genome to that of the model organism Medicago. Project scientists conducted variety performance trials on a new novel endophyte tall fescue population toward release of an improved variety for cattle (specifically greater persistence and productivity with greater palatability). Entomologists contributing to the project completed research evaluating soft-textured, non-spiny tall fescue cultivars containing novel (livestock-safe) endophytes for resistance to insects and found that there was no increased vulnerability of these fescues versus the prevalent toxic Kentucky-31 tall fescue cultivar. Project scientists investigating Near Infrared Spectroscopy (NIRS) for use in predicting grazing horse diet composition discovered a strong correlation between the NIRS scans and the actual diet composition of test horses. Thus, this system is being explored further as a rapid screening system for aiding producers in making pasture management and horse nutrition decisions.
1. Understanding tall fescue/fungal endophyte effects on nutrient cycling in southeastern U.S. pastures. Localized research from Georgia found that endophyte-infected tall fescue pastures supported larger soil nutrient pools, suggesting that this important agricultural plant-fungal endophyte symbiosis plays a role in carbon sequestration and promoting soil fertility. An experiment was conducted to investigate whether this finding was geographically robust (i.e., found at multiple sites). ARS scientists at Lexington, KY, identified and sampled >13 tall fescue pastures, with paired, adjacent endophyte-infected and endophyte-free plots, located throughout the southeastern United States. Surface soils were analyzed for organic carbon and total nitrogen and microbial community composition and biomass. We found that the Georgia findings are robust in that endophyte-infection appears to enhance the ability of tall fescue pastures to store carbon and enhance soil fertility across the southeastern U.S., although effects on the microbial communities are less pronounced. These results highlight that the tall fescue–endophyte symbiosis can have significant environmental impacts in addition to well known animal health issues, and suggest that more research is needed to understand the mechanisms producing these results.
2. Chemical suppresion of seedhead emergence to mitigate fescue toxicosis. Tall fescue is a cool-season perennial grass extensively utilized for grazing and hay production on approximately 15 million hectares. A fungal endophyte infects tall fescue plants and produces ergot alkaloids that cause fescue toxicosis. Cattle selectively graze tall fescue seedheads, which can be problematic because ergot alkaloid concentrations in seedheads are greater than in leaf blades and sheaths. Chaparral® herbicide, applied early in vegetative growth, can suppress seedhead emergence in tall fescue to potentially mitigate fescue toxicosis and enhance calf weight gain. However, pasture carrying capacities could be substantially reduced compared to tall fescue without chemical suppression of seed heads. An experiment was conducted that evaluted steer and pasture responses to seed head suppression with light and moderate grazing intensities. Results showed reduced carrying capacities with seed head suppression, but higher steer weight gains with the treatment compensated for the lower capacities in generating weight gains per acre that were similar to those of untreated pastures. This management approach provides a way to improve the efficiency of backgrounding beef calves on toxic endophyte-infected tall fescue for feedyard finishing.
3. Novel endophyte-infected tall fescue - livestock safe, but pest resistant. Above- and below-ground herbivores (pests) were sampled across two growing seasons in pastures containing common endophyte-infected (E+, Kentucky-31), novel endophytes (MaxQ or AR584), or endophyte-free (E-) tall fescue. Natural enemies, too, were sampled for possible tritrophic effects. Chewing (grasshoppers, crickets, caterpillars), sucking (leafhoppers, planthoppers) and root-feeding (scarab grubs) pests were no more abundant in pastures with "livestock-friendly" (i.e., novel endophytes) endophytes than in ones with common endophyte. That conclusion was also supported by lab feeding assays using armyworm (Mythimna unipuncta), an important irruptive pasture pest. Results suggest that re-seeding common strain endophytic pastures with livestock-friendly novel endophyte/grass associations to alleviate fescue toxicosis is unlikely to encourage ourbreaks of plant-feeding insects.
4. Soft or abrasive, which is better for insect resistance. An experiment was conducted to test how the use of soft-textured, improved forage grasses with non-spiny leaf margins may affect susceptibility of the armyworm, an irruptive pasture pest, to natural suppression by an insect virus important in suppressing the pest's populations. Larvae were fed virus doses on smooth or spiny-edged cultivars or on grass blades with spiny edges intact or physically removed. Mortality was similar with spiny- or smooth-edged grass. Electron microscopy showed that despite their sharpness, the grass edge spines did not abrade or puncture the lining of the insect's gut to facilitate infection. Thus, increased use of smooth-edged forages, which are more palatable to livestock, will not reduce the benefits of natural biological control by the virus. The virus worked with was one found to cause epizootics and drive down armyworm outbreaks in Kentucky pastures. It turned out to be a new virus species that has potential for development as a microbial insecticide.
Dinkins, R.D., Tavva, V.S., Palli, S.R., Collins, G.B. 2011. Mutant and overexpression analysis of a C2H2 single zinc finger gene of Arabidopsis. Plant Molecular Biology Reporter. 30:99-110.