Grass-birdsfoot trefoil mixtures to improve the economic and environmental sustainability of pasture-based organic dairies in the western U.S.

Project Overview

Project Type: Research and Education
Funds awarded in 2017: $214,123.00
Projected End Date: 03/31/2021
Grant Recipient: USDA-Agricultural Research Service
Region: Western
State: Utah
Principal Investigator:


  • Agronomic: grass (misc. perennial), trefoil
  • Animals: bovine
  • Animal Products: dairy


  • Animal Production: grazing - multispecies, grazing - rotational, rangeland/pasture management
  • Crop Production: nutrient cycling, organic fertilizers
  • Education and Training: extension, on-farm/ranch research, workshop
  • Farm Business Management: budgets/cost and returns
  • Production Systems: organic agriculture

    Proposal abstract:

    With over 3.5 million milk cows in the western U.S., dairy is a dominant sector of western
    agriculture, and pasture-based organic dairies are becoming more prevalent in the region.
    Organic milk is marketed for the health and environmental benefits of pasture-raised milk;
    however, organic dairies using the most pasture forage (75-100%) have the lowest net returns
    due to a 32% decrease in milk production. Reduced dry matter intake (DMI) by grazing dairy
    cows is one of the major factors limiting milk production. Moreover, dairy cattle breeds are
    finicky-grazers, resulting in even lower DMI of traditional pasture species like tall fescue. Dairy
    herd fertility is critical to dairy sustainability, but nutrient-rich pastures may reduce pregnancy
    rates further complicating pasture-based dairy.
    Previous WSARE research (SW10-088) demonstrated that mixtures of tall fescue and the
    condensed-tannin containing legume, birdsfoot trefoil (BFT) improved beef steer performance.
    Critical questions, particularly for pasture-based dairy include, are there grass-BFT mixtures that
    increase both tannins and energy, and what will be their synergistic effect on dairy cattle
    performance? This research proposes to use university and on-farm trials to assess dairy heifer
    DMI, health, reproductive performance, economics, and impact on nitrogen cycling in response
    to grazing grass-BFT mixtures containing various protein, energy, preference, and tannin levels.
    An innovative outreach plan will reach a diverse audience of producers, educators, and the
    public, and include traditional field tours and web-based outlets such as eOrganic. These
    objectives are in direct response to stakeholder feedback, and it is anticipated that pasture
    mixtures will be identified that improve the sustainability of organic pasture-based dairy.
    Preliminary (1-year) data were obtained via a small seed-grant and indicated that heifer gains
    were 60% higher when grazing high-energy-grass-BFT mixtures as compared to low-energygrass-monocultures.
    Additional funding will support expanding the research scope, including
    grazing evaluation, heifer reproductive performance, on-farm trials, and outreach.

    Project objectives from proposal:

    Objective 1. Determine relative forage production and dairy cattle DMI in response to
    grazing grass-legume mixtures containing various tannin, protein, and energy levels.
    Hypothesis: We hypothesize that increasingly greater inherent grass energy concentrations will
    act synergistically with low levels of condensed tannins in birdsfoot trefoil to improve dairy
    heifer dry matter intake and performance when grazing grass-birdsfoot trefoil mixtures.
    Sub-objective 1.1. Determine dairy heifer performance and DMI. Determine dairy heifer
    DMI and performance, forage mass, and forage nutritive value when rotationally grazing
    replicated grass-legume pastures characterized by various levels of herbage, tannins, protein,
    energy, fiber, and livestock preference. Analyses will determine which forage characteristics
    (e.g., protein, energy, etc) primarily contribute to differences in heifer DMI and performance.
    Sub-objective 1.2. Planting method effect on BFT establishment, persistence, and heifer
    utilization. Determine relative BFT establishment, persistence, and utilization when grass-BFT
    mixtures are drilled together in same row compared to alternating rows of grass and BFT.
    Sub-objective 1.3. Validation using on-farm trials. Grass and BFT treatments will be planted
    on existing pasture-based dairies (producer participants), and producers will estimate herbage
    and utilization. Data will be analyzed, compared to USU pastures, and presented at field days.
    Objective 2. Assess dairy heifer health, growth, and reproductive performance in response
    to grazing grass-legume mixtures containing various protein, energy, and tannin levels.
    Hypotheses: We hypothesize that animal growth and reproductive performance and overall
    animal health will be slightly reduced in organic, pasture-raised heifers compared to TMR-fed
    control animals. However, we hypothesize that heifers grazing grass/legume mixtures will grow
    faster and be more reproductively competent than heifers grazing grass-only pastures.
    Sub-objective 2.1. Describe the effect of dietary treatments on key growth parameters,
    including gross anatomical measurements as well as systemic markers of growth. Determine
    effect of excess dietary protein from nutrient-rich pastures on Blood Urea Nitrogen and other
    systemic markers of growth. Results will be compared to predict which plant species best meet
    nutritional requirements for dairy heifer growth and reproductive fertility.
    Sub-objective 2.2. Evaluate markers of animal health, including parasite load. The parasite
    load (fecal egg count) within the gastrointestinal tracts of the growing heifers will be determined
    for individual animals within each treatment and compared to systemic growth markers.
    Sub-objective 2.2. Effect of excess dietary protein on conception and early embryo
    development. Embryos will be flushed from heifers and evaluated for number and quality.
    Conception rates will be determined. Data will be analyzed to determine the effect of pasture and
    excess dietary protein on superovulation response, embryo recovery, and embryo quality.
    Objective 3. Determine pasture-based dairy impact on nitrogen cycling in response to
    grazing grass-legume mixtures containing various protein, energy, and tannin levels.Hypothesis: We hypothesize that the addition of tannin-containing legumes will reduce nitrogen
    loss compared to grass monocultures under various protein and energy levels.
    Sub-objective 3.1. Impact of BFT tannins on nitrogen cycling. A mass balance approach will
    compare nitrogen outputs (plant material, soil, leachate) against nitrogen inputs.
    Sub-objective 3.2. Impact of increased plant energy on nitrogen cycling. Same approach as
    sub-objective 3.1 to compare high- and low-sugar grasses.
    Sub-objective 3.3. Impact of root structure on N capture. Evaluate the impact of different
    grass species and their root structure on nitrogen capture.
    Objective 4. Conduct a comprehensive assessment of the economic sustainability of the
    various forage-based heifer development programs proposed herein.
    Hypothesis: We hypothesize that grass/legume mixtures for heifer development will be more
    economically sustainable than monoculture grass, and, further, if there is an adequate organic
    dairy heifer premium, it may also be more economical than TMR-based heifer development.
    Sub-objective 4.1. Determine the cost differences from each of the heifer development
    programs. Costs associated with developing each of the different pasture based program
    treatments will be determined and compared to the cost of dry-lot heifers on TMR.
    Sub-objective 4.2. Quantify the impact of the animal performance on the economic value of
    the dairy heifers and determine the most profitable method of raising the dairy heifers.
    Actual costs differences and revenue differences from the alternative heifer development
    programs will be combined to determine the program that offers the greatest economic return.
    Objective 5: Execute an innovative and impactful outreach program on the successful
    implementation of grass/legume grazing for organic dairy production systems.
    Outreach plan: Enhance communication among producers, processors, marketers, researchers,
    and Extension personnel by building an interactive communications network facilitated by eOrganic
    and Utah State University and University of Idaho Extension.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.