- 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
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.