Location: Rangeland and Pasture Research2018 Annual Report
1a. Objectives (from AD-416):
The vision of this research is to increase the ecological and economic sustainability of forage-based livestock production systems associated with the Southern Plains mixed-grass prairie. Our strategy is to minimize environmental impacts and increase the efficiency of plant and animal resources while addressing the production and conservation goals of the Southern Plains mixed-grass prairie. During this bridging project, we will continue to focus on these following objectives: Objective 1: Develop enhanced germplasm of eastern gamagrass, sand bluestem, little bluestem, and Texas bluegrass for improved forage yield, forage quality, seed yield, and stand persistence. Objective 1A: Breed eastern gamagrass cultivars with improved biomass yield and other performance traits. Objective 1B: Continue to develop a diallel population of sand bluestem from 15 diverse accessions. Objective 1C: Breed little bluestem cultivars with improved forage and seed production. Objective 1D: Breed and evaluate pure Texas bluegrass and interspecific hybrids with improved performance traits. Objective 2: Develop perennial sorghum-based, interspecific, and wide hybrids with high sugar content for livestock and biofuel production on the Southern Plains. Objective 3: Evaluate the potential for using patch-burning and supplementation strategies on rangelands to improve the productivity of stocker cattle and beef cows while enhancing other ecological services. Objective 4: Evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. Objective 5: Evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and determine the environmental benefits of these grasses relative to other forages, and/or cropping options.
1b. Approach (from AD-416):
To identify germplasm with superior traits, expand the limits of germplasm variation by wide hybridization using interspecific and intergeneric introgression and genetic manipulation, evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and then release superior germplasm and improved cultivars. Broad-based germplasm collections of eastern gamagrass, Texas bluegrass, little and sand bluestems are maintained at the Southern Plains Range Research Station in Woodward, OK. Further, a major resource problem is over-used rangeland, making it susceptible to erosion and weeds, also compromising other ecological services. The challenge is to develop economic, energy-efficient forage grazing systems for the Southern Plains while maintaining or improving ecological service to wildlife and society. This research will employ basic agronomic, animal performance, plant and animal physiology, genetics, cytogenetic, and molecular biology experiments.
3. Progress Report:
Progress was made in all three objectives of this project from FY17 to FY18, all which fall under National Program 215, Pastures, Forages, and Rangelands. Objective 1 of our project was to develop enhanced germplasm of native grasses for improved forage yield, forage quality, seed yield, and stand persistence. Subobjective (1B) was to develop a diallel population of 11 sand bluestem lines. We completed all the crosses and have viable seed for most combinations. After reducing the number of accessions to eleven, we have several seeds in all 110 possible crossings (cells). Now that we have met our goal of having greater than 10 seeds in every cell, a new scientist can complete the genetic and performance analysis that will aid in the development of superior cultivars of this extremely productive grass unique to the Southern Plains. In the third subobjective (1C), we bred little bluestem with improved forage and seed production characteristics. In this subobjective, we continued to narrow the little bluestem populations to meet our goals of improving forage and seed production in this species. These germplasm lines will be useful for the breeding and development of new cultivars intended for many purposes, such as: wildlife habitat, livestock grazing, soil stabilization, and biomass for renewable energy. Starting in FY18 we planted these advanced lines at Woodward, Oklahoma, Knoxville, Texas, Enid, Oklahoma, and Manhattan, Kansas. This research has shown that selection for greater germination at a low water potential produces germplasm lines with greater stand emergence and plant densities in the field. In the fourth subobjective (1D), a selection of seeds from the D4 Texas bluegrass ecotype that germinates at lower water potentials were planted in isolation nurseries and seed was harvested in April 2016. Seeds from promising hybrids, that are now under evaluation, were harvested from plants in the field. For Objective 2, we have discontinued work on this project because the lead scientist has left the position, we will attempt to restart the project after the position is filled. Objective 3 in our project is to evaluate the potential for using patch-burning and supplementation to improve the productivity of cattle and enhance ecological services. The experimental plots were established in 2007 and we have completed 2.50 burn cycles with delays occurring in two of the 11-years because of drought and burn bans. With a goal to complete 4 burn cycles during this 16-year experiment, we are on schedule to complete this experiment and summarize the data in 2024.
1. Whole cottonseed supplementation improves performance and reduces methane emission intensity of grazing beef steers. A method for mitigating enteric methane emission has been the use of medium-chain fatty acid supplementation by an ARS scientist in Woodward, Oklahoma. The objective of this experiment was to determine the effect of the level of whole cottonseed supplementation (20% fat) on average daily gain and enteric methane emissions of steers grazing tallgrass prairie in the summer. Steers were offered from 0 to 2.9 kilograms/day (as feed) of whole cottonseed in individual feeders for 43 days. Body weight was measured weekly before feeding. Total fat concentration of the diet (supplement + forage) at the greatest supplement intake was estimated to be 8.3% of dry matter resulting in body weight gain increasing linearly as supplement intake increased. Supplemented steers tended to respond quadratically to supplement intake, with minimal methane emission at a supplementation rate of 2.0 kilograms of supplement per day. Emission intensity (grams of methane emitted/kilograms of body weight gained) also responded quadratically across supplementation rates and was minimized at approximately 2.2 kilograms of supplement intake per day. The results of this research suggest that if cattle producers use whole cottonseed supplementation to mitigate methane emission while cattle are grazing tallgrass prairie in the early summer, an amount of approximately 2 kilograms/day is optimal.
Beck, M., Thompson, L., White, J., Williams, G., Place, S., Moffet, C., Gunter, S.A., Reuter, R. 2018. Whole cottonseed supplementation improves performance and reduces methane emission intensity of grazing beef steers. Professional Animal Scientist. 34:339-345. https://doi.org/10.15232/pas.2018-01722.