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United States Department of Agriculture

Agricultural Research Service

Research Project: Grass-Legume Mixtures to Enhance Sustainability of Irrigated Pastures

Location: Forage and Range Research

2011 Annual Report


1a.Objectives (from AD-416)
(1) Compare livestock performance, economics, and subsequent carcass characteristics from beef grazing grass monocultures and low- and high-tannin grass-legume mixtures versus traditional feedlot-based finishing; (2) Determine best possible grass-legume mixtures and plant densities that maximize pasture productivity and nutritional quality; and (3) Determine the effects of tannins on nutrient cycling in grazing systems.


1b.Approach (from AD-416)
To compare livestock performance, economics, and subsequent meat quality of beef produced from grass monocultures versus low- and high-tannin grass-legume mixtures.

(1) Determine if tall fescue (TF)-legume mixed pastures will enhance livestock performance (ADG, feed efficiency, intake, and nutrient digestibility) and to compare if the animal performance will be further improved when animals are grazed on TF-birdsfoot trefoil (BFT) mixed pasture; (2) Investigate in vitro fermentation characteristics of forage pastures used in grazing study with emphasis on microbial protein synthesis and ruminal fatty acid (FA) composition; (3) Assess how different compositions of pasture alter carcass characteristics and beef quality; (4) Determine the differences in the FA composition of beef from pasture-finished vs. feedlot-finished cattle and the time required for changes in FA composition to occur; and (5) Assess the economics and barriers to adoption of grazing-based beef production, develop an effective extension program to facilitate the adoption of grazing management for beef production, and create an awareness of the beneficial nutrient management and other environmental impacts of such an exchange.


3.Progress Report

The objective of this project was to determine the production, environmental, and economic potential of grass-legume pastures in comparison to fertilized and unfertilized grass monocultures. The project has three components including evaluating livestock performance and carcass quality when grazing mixtures, determine optimum grass-legume mixtures, and determine the effect of high-tannin legumes on nitrogen-based environmental impacts. Livestock performance was evaluated using large plots (0.5 ha) of tall fescue monocultures, tall fescue-legume mixtures (alfalfa and birdsfoot trefoil), and feed-lot. Treatments to determine mixtures for optimum pasture productivity included small plots of binary mixtures of grasses and legumes.

During FY-2011: The work outlined in the SOW was initiated. It was discovered that legumes had died out of previously established pastures. These tall fescue-legume (alfalfa and birdsfoot trefoil) pastures were re-established in 2011. However, the graduate student on this project used the existing pastures to collect a second year’s data on livestock intake and gains, fatty acid profiles, ruminal pH and ammonia, and forage production and quality comparing tall fescue with and without N-fertilizer and feedlot treatments. Preliminary results were presented at the Annual Meeting of Western Section, American Society of Animal Science in June 2011 and at the Joint Annual Meeting of ADSA-ASAS in July 2011, and indicated that applying N fertilizer to tall fescue did not influence growth performance or carcass characteristics.

Additional research initiated during FY2011 included installation of lysimeters during the re-establishment of the tall fescue-legume pastures, which were used to determine the initial nitrogen in the leachate. These pastures will be grazed next year. The small plots of binary mixtures of five grasses (orchardgrass, tall fescue, meadow brome, timothy, and perennial ryegrass) and three legumes (alfalfa, birdsfoot trefoil, and cicer milkvetch) were established and data collection was begun. Ratios in the mixtures included 0, 25, 50, and 75% legume composition. Samples from these plots were used to initiate development of an NIRS equation that can determine composition of legume in mixture plots.

Monitoring Methods: The ADODR monitored this research via email, phone calls, personal meetings with the cooperator, and site visits to the field locations.


Last Modified: 10/20/2014
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