Location: Livestock and Range Research Laboratory2018 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop management strategies to improve rangeland cattle production and ecological stability in the northern Great Plains through effective use of rangeland forage resources, precision supplementation, and livestock with greater adaptability to climatic, physiological, and nutritional stress. Sub-objective 1.1 Determine effects of dormant rangeland forage utilization on heifer development, plant productivity, and species composition. Sub-objective 1.2 Develop nutritional management for post-weaning heifer development to complement annual and weather-driven fluctuations in forage availability and quality. Sub-objective 1.3 Estimate effects of vegetation, climate, and environmental variables on cattle growth. Sub-objective 1.4 Develop mineral supplement and water amendment strategies to ameliorate weather-induced changes in naturally occurring rangeland stock water quality. Sub-objective 1.5 Develop a molecular barcode system for northern mixed-grass prairie plant species that will enable future description of plants consumed by livestock on rangelands. Objective 2: Develop management strategies integrating grazing, fire, and chemical practices to restore rangelands degraded by weeds and prevent weed invasions in the northern Great Plains. Sub-objective 2.1 Develop fire and herbicide treatment combinations to reduce annual brome abundance in rangelands. Sub-objective 2.2 Develop effective practices to rehabilitate rangeland riverine sites that have been mechanically and chemically treated to eradicate Russian olive. Sub-objective 2.3 Identify and develop effective reclamation strategies for converting coal mining lands back to livestock grazing lands. Sub-objective 2.4 Determine physiological traits allowing perennial seedlings to use dormancy to survive unfavorable environmental conditions. Objective 3: Develop adaptive strategies for managing the interacting effects of livestock grazing, fire, and climatic variation on northern Great Plains rangelands to increase the stability of livestock production while maintaining ecosystem health. Sub-objective 3.1 Quantify grazing season and intensity effects on plant community composition and productivity. Sub-objective 3.2 Quantify interacting effects of climate with defoliation timing and intensity on rangeland stability. Sub-objective 3.3 Determine rangeland community response to autumn defoliation intensity. Sub-objective 3.4 Determine post-fire weather effects on plant community response to summer fire. Sub-objective 3.5 Determine the effect of mycorrhizal fungi and different levels of simulated grazing on plant community composition and measures of soil health. Sub-objective 3.6 Determine plant and soil community response to fire return interval and seasonality.
1b. Approach (from AD-416):
Sustainability of rangeland production hinges on the stability of plant communities because changes in species composition, forage production, and forage quality fundamentally affect the animal community. The primary forces of change in rangelands are weather, grazing, alien plants, and fire. This project is designed to improve ecological sustainability and rangeland production by addressing opportunities for increased efficiency of livestock nutrient conversion, mechanisms affecting restoration success, and interacting effects of disturbances with weather and climate. We propose improved efficiency of nutrient conversion from dormant rangeland forages is among the most viable options for increasing animal production and minimizing effects on plant communities. We will address this proposition through a series of experiments evaluating plant and animal responses to dormant season utilization and supplementation strategies. Rangeland restoration methods will be evaluated for direct weed control and mechanisms controlling successful establishment of desirable species. Water manipulations will be included in multiple experiments to determine weather and long-term climate effects because precipitation is the primary controlling factor for plant productivity and community composition. Experiments will be integrated across objectives to determine interacting effects of precipitation, grazing, weeds, and fire on soil and plant communities (production, species composition, diversity, propagation, survival) and cattle (weight gain, reproductive performance, diet quality, diet selection). Understanding the mechanisms that control rangeland stability and animal responses to alterations in plant communities will assist land managers and livestock producers in improving rangeland integrity and efficiency of livestock production. Results will also provide scientists greater understanding of the complex interacting forces on rangelands.
3. Progress Report:
During the 6 months of the bridging project we have primarily been processing and analyzing data from the last field season while awaiting a new research project to be approved by National Program staff. Monitoring and data collection have continued for all long-term work including development of effective reclamation strategies for converting coal mining lands back to livestock grazing lands (Objective 2.3); examining grazing season and intensity interactions (Objective 3.1 and 3.3); determining long-term interactions between climate and defoliation treatments (Objective 3.2); and fire seasonality-frequency research (Objective 3.6) continued. Sites used for effects of dormant rangeland forage utilization on heifer development (Objective 1.1) were prepared for transition to the upcoming Beef Grand Challenge project to be started this fall. Determination of physiological traits allowing perennial seedlings to survive unfavorable environmental conditions (Objective 2.4) was extended to allow longer evaluation of plant survival. DNA metabarcoding is a promising tool for quantifying cattle diet (dissimilarity) in rangelands and may help explain animal-to-animal variation in feed efficiency (Objective 1.5). DNA metabarcoding utilizes small DNA fragments, common in complex degraded (e.g. fecal) samples, to describe diet composition (i.e. barcodes). Unclear is whether such data provide only qualitative (e.g. species present or absent) or quantitative data on diet similarity as well. We constructed 24 complex mixes (4 to 16 plant species per mix) containing a gradient in similarities and quantified all pairwise diet compositional similarities. Next, we will quantify similarity estimates based on DNA metabarcoding of control (undegraded) and degraded (digested) samples. These data will be used to quantify the accuracy of this new technology and test whether two types of correction factors appreciably improve DNA metabarcoding data quality. To make our inferences more generalizable, we included treatments for two of three major digestion types (hindgut and foregut fermentation). Digestion treatments included a grasshopper feeding assay (hindgut fermentation) and a 2-stage in-vitro rumen digestion (foregut fermentation) simulating cow digestion. The two digestion experiments have been completed. DNA has been extracted from all experimental and reference samples (reference library of 311 plant species, 91% of the plants known to occur at Miles City, Montana). Tagging and PCR protocols have been developed and the research is progressing. This work is being continued through sub-objective 1.D in the proposed research project.