Location: Livestock, Forage and Pasture Management Research Unit
2025 Annual Report
Objectives
Objective 1. Evaluate production efficiency in reproductive beef cattle within conventional and unconventional production systems in the Southern Great Plains.
Sub-objective 1.A: Quantify dynamics of C and energy balances of southern tallgrass prairie in response to grazing systems, prescribed burns, and biophysical factors.
Sub-objective 1.B: Evaluate the rumen biome of cows managed on different pasture types.
Objective 2. Evaluate nutrient-use and production efficiency in terminal beef cattle within conventional and unconventional forage-based growing and finishing systems in the Southern Great Plains.
Sub-objective 2.A: Define the value of annual forage mixes as sources of ecosystem services in warm-season row crop rotations: livestock performance, soil condition, C, and energy budgets.
Objective 3. Utilize new and existing technologies to remotely improve herd health monitoring, and improve management practices for increased overall system efficiency and sustainability.
Sub-objective 3.A: Evaluate body condition, reproduction efficiency, and rumen microbiome of cows under different systems of pasture-based management.
Approach
Over the last half century, annual U.S. beef production has increased with fewer cows in the national herd by harvesting larger animals. While feed costs represent the single largest expense in beef production, less than 20% of the post-weaning feed energy consumed is converted to edible product. As competition for and the price of feed-grains increases due to growing global human population, use of grains for energy production, and other requirements, beef production enterprises will need to transition from greater grain/inputs dependency to greater reliance on forage resources (pasture and rangeland) produced on lands not suitable for more intensive crop production. We propose to increase on-farm forage system nutrient quality during the typical dormant season, reduce outside-sourced supplement dependence, and evaluate multiple forage systems for efficiency in terms of water, soil, and nutrient supply. The research effort will allow for improvement in efficiency and sustainability of forage-based cow/calf and beef cattle production systems within the southern Great Plains. Additionally, evaluation of animal genetic by forage system management/type interactions will further allow the improvement of forage-based production systems in the Southern Great Plains (SGP) and globally. The end result will be improved efficiency of beef production from enhanced grassland-, pasture-, and forage-based systems with less grain and fossil fuel inputs, less need for capital through increased use of on-farm products, and increased competitiveness and profitability for producers. To accomplish this goal, the impact of animal genetics and management interactions on animal/system nutrient-use efficiency, health, and the beef system components must be better understood.
Progress Report
With respect to Sub-objective 1.A, the project has had delays due to critical vacancies and weather (e.g., prior experiments utilizing the land resource required an additional year of study to complete a prescribed burn and make subsequent measurements). ARS researchers at El Reno, Oklahoma, are establishing four of the Eddy Covariance (EC) systems needed for the study in preparation for this coming winter. With respect to Sub-objective 1.B, ARS researchers at El Reno, Oklahoma, continued to collect soil and plant community data this year. Replication of the green manure and grazing rotation treatments for Sub-objective 2.A were planned for this year so they could be compared with wheat pasture, but due to drought, the green manure/graze rotation pastures were not grazed. Another year will be needed for the study to collect comparison data. EC systems have, however, continued to collect data, soil/plant samples are being collected, and animal body weight data were collected in the wheat pastures. An ARS scientist has recently been hired to fill one of the vacancies in the project and a scientist was also hired this FY under a cooperative agreement with Texas A&M AgriLife that will be working, in particular, on Sub-objectives 1.B and 3.A that have been delayed.
Accomplishments
1. Energy intake by cattle successfully estimated with respiration gas fluxes. Understanding the intake and use of energy in forages consumed by cattle is an important part of predicting their performance while they graze pasture or fed in groups. Such knowledge is important for describing the growth efficiencies of cattle, and in identifying and developing the types of cattle that would be useful to commercial herds. ARS scientists at Woodward, Oklahoma, used an automated head-chamber system that takes multiple measurements of oxygen, carbon dioxide and methane in animal breaths over short periods to calculate the intake of gross, digestible, and metabolizable energy by cattle. These measurements of respiration gases, combined with measurements of body weight and average daily gains, allowed the calculation of energy gained from forage digestion that was used in maintenance by the animal for respiration and energy retained in the body as growth. This approach showed that measures of energy intake have high precision and good accuracy when they are made over a longer period on pasture or feeding. Hence, automated head-chamber systems can serve as a viable tool to evaluate the energetic efficiency of cattle in open-air environments and be useful for researchers and suppliers of premier seedstock.