Source: UNIVERSITY OF VERMONT submitted to
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
Funding Source
Reporting Frequency
Accession No.
Grant No.
Project No.
Proposal No.
Multistate No.
Program Code
Project Start Date
Sep 1, 2023
Project End Date
Aug 31, 2027
Grant Year
Project Director
Darby, H. M.
Recipient Organization
Performing Department
Non Technical Summary
Consumer demand for 100% grass-fed dairy products continues to rise. Dairy producers are seeking information about successful transition and management of grass-based dairy systems that maintain herd health and production, milk quality, and farm economics. Producers also seek information on management practices and strategies that support financial viability. Our specific objectives include enhanced data collection on cost of production, economical soil and forage production and management, animal husbandry and nutrition, and milk nutritional and sensory quality. This project aims to increase the success and viability of grass-fed dairy production operations by conducting research and education programs that address the needs of farmers, stakeholders, and consumers.The information generated from this project will be disseminated through a combination of education and outreach strategies to encourage learning and improvement of grass-fed management practices across a wide range of farms located throughout the U.S.
Animal Health Component
Research Effort Categories

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
Goals / Objectives
Our overarching goal is to build on the knowledge gained through our recent OREI (2018-02802) to address remaining knowledge gaps in practices and strategies at the soil, plant, and animal levels that maximize farm success and viability into the future. While our research provided essential foundational understanding of these systems and their unique challenges, additional needs for both research and education emerged that must be addressed to further production, consumption, and farm viability. Our specific objectives below include enhanced data collection on cost of production, economical soil and forage production and management, animal husbandry and nutrition, and milk nutritional and sensory quality. This project aims to increase the success and viability of grass-fed dairy production operations by conducting research and education programs that address the needs of farmers, stakeholders, and consumers.Project objectives: Our interdisciplinary team, with the guidance from our major stakeholders, aims to enhance grass-fed dairy production through the following objectives:Objective 1: Identify key management strategies that enhance farm viability through expanding economic benchmarking.Objective 2: Understand grazing and youngstock management impacts on internal parasitism risk, animal health and productivity, and markers of ruminal development.Objective 3: Identify soil and forage management strategies that enhance forage productivity and quality and are resource efficient.Objective 4: Understand the nutritional and sensory quality of grass-fed milk to inform market growth and expansion strategies.Objective 5: Strengthen knowledge, skills, and networks among farmers, processors, and technical service providers.
Project Methods
Objective 1.1-Expand the data collection and participants in the financial benchmarking program: Through this project we aim to expand our financial Benchmark program to include at least 30 grass-fed dairy farms annually over 3 years. Data will be entered into the DairyTRANS workbook that was updated for grass-fed producers through the last project.Objective 2.1- Quantify the impacts of grazing management on gastrointestinal parasite burden in organic grass-fed dairy cattle and identify impact on milk production: In year 2, ten lactating herds will be monitored over the grazing season for gastrointestinal parasite burden and milk production. Fecal Egg Counts (FEC) will be taken at turnout and repeating every 4 weeks. Samples of freshly dropped cattle dung (n=10) will be collected and taken to the laboratory for copromicroscopic diagnosis of GIN infection. Milk production in these herds will be monitored by DHIA report data.Objective 2.2- Investigate impact of grazing management and calf milk feeding (quantity and duration) on youngstock resiliency to gastrointestinal parasites, breeding performance and productivity in first lactation: In years 2-3 of the project, a subset of 10 farms will be selected and fecal samples will be taken from calves for FEC to assess parasitism at first turnout and every 3 weeks over the grazing season. For these farms, ongoing survey data will be collected relating health, reproductive and breeding outcomes, and DHIA reports will be used to follow milk productivity during first lactation.Objective 2.3- Evaluate the interaction of forage quality and milk feeding duration on calf and heifer growth and markers of ruminal development: In years 2-3, a feeding trial will be conducted at the University of New Hampshire. Forty-eight newborn dairy calves will be assigned to the experimental diets in a randomized complete block design with a 2 x 2 factorial arrangement of treatments. All calves will receive 4L of colostrum in the first 12h of life. On d2 of life, calves will be fed 6L/d milk until d14, followed by 8L/d from d15 to 21, and 10L/d from d22 to 90 (short) or d22 to 180 (longer milk duration). Calves will be blocked by birth date and sex and, within block, randomly assigned to 1 of 4 treatments as follows: 1) low-quality alfalfa-grass hay+ milk for 3 months, 2) low-quality alfalfa-grass hay + milk for 6 months, 3) high-quality alfalfa- grass hay + milk for 3 months, and 4) high-quality alfalfa-grass hay + milk for 6 months. The experiment will continue until heifers and steers reach 9 months of age to fully evaluate the impact of weaning (3 or 6 months) on growth and markers of ruminal development. Measurements will include daily DMI, bi-weekly BW, and skeletal measures along with blood samples for indicators of ruminal development.Objective 3.1- Identify management strategies that enhance forage productivity and quality: The experimental design will be a randomized complete block with four replications and a factorial arrangement of two treatment factors: 1) 3 grass species and 2) N treatment. Total N supplied via applied amendments will be held constant across the treatments except for the control which will have no N, and a second chilean nitrate treatment applied at twice the N rate as the other products. At each harvest, DM yield and forage quality will be measured. Prior to each harvest, 5 soil cores will be collected within each plot to a depth of 30cm and analyzed for nitrate and ammonium.A second experiment will compare the N supply provided to a companion perennial grass from several legume inclusion rates. The experimental design will be a randomized complete block with four replications and a factorial arrangement of three treatment factors: 1) grass species, 2) legume inclusion, and 3) N fertilizer rate. The first factor will include two perennial cool season grass species. The second factor will be inclusion of alfalfa at 0, 25, 50, or 75%. The third factor will be N fertilizer rate of 0, 25, and 50 kg N ha-1 as Chilean nitrate.Objective 3.2- Characterize soil nutrient dynamics on grass-fed dairy farms: Soil fertility status will be surveyed on approximately sixty fields from organic grass-fed dairy farms in VT, NY, OH, and PA to characterize trends related to production. Just prior to first harvest soil samples will be collected from a 5m x 5m area by compositing 10 soil cores. Samples will be collected from the 0 to 15, 15 to 30, and 30 to 60 cm depths and analyzed for pH, carbon, nitrogen, and extractable P and K. Samples from the 0 to 15 cm depth will also be analyzed for buffer pH, organic matter, extractable Ca, Mg, B, Mn, and Zn.Objective 3.3- Evaluate the interaction between forage quality and molasses supplementation level on ruminal fermentation and methane emissions: A four-unit dual-flow continuous culture fermentor system (Dillard et al., 2019) will be inoculated with rumen fluid from dairy cows managed under Penn State Institutional Animal Care and Use Committee protocols. In Year 1, treatments will be in a 2 x 2 factorial arrangement as follows: 1) high-quality herbage plus liquid molasses at 10% of total DM fed; 2) high-quality herbage plus liquid molasses at 5% of total DM fed; 3) low-quality herbage plus liquid molasses at 10% of total DM fed; and 4) low-quality herbage plus liquid molasses at 5% of total DM fed. Fermentors will be operated for four, 10-day periods. Effluent samples will be collected on days 8 to 10 for analyses of DM, ammonia-N, volatile fatty acids, and bacterial protein synthesis. Samples of diet and effluent will be analyzed for DM, organic matter, crude protein, fiber, starch, water soluble carbohydrates, and minerals. Nutrient digestibility and methane output will be quantified per the methods of Dillard et al. (2018).Objective4.1- Expand understanding of grass-fed milk sensory quality's relation to farm management and processing: Three lots of processed grass-fed milk will be collected from each of the three major regional processors, every other month, over a three-year period. In addition, we will collect market samples from nine randomly chosen retail outlets in the Northeast each quarter. Lastly, we will collect raw milk samples from randomly selected grass-fed milk farms that supply the three major producers. We expect to assess raw milk samples from at least three farms per regional processor per quarter. Raw milk samples will be pasteurized at UVM. They will then be chilled and presented to the DSA panel blindly in a random order to be evaluated cold, in triplicate using the PAA and QI methods. An aliquot of each sample that is assessed by the UVM DSA panel will be submitted for fatty acid and β-carotene analysis as described below.Objective 4.2 Identify the β-carotene content and fatty acid content and profile in grass-fed milk to assess their applicability as potential biomarkers of authentication of grass-fed milk as well as the nutritional quality of grass-fed milk: We will conduct a study on grass-fed farms to perform an intensive sample collection to robustly determine and quantify the content of fatty acids and β-carotene in grass-fed milk. Over a period of two years, we will collect weekly milk samples at six grass-fed farms and determine the fatty acid content and profile and β- carotene. In addition, other milk types, such as conventional milk and organic non-grass-fed milk, will be collected in parallel and used as a reference. Milk will be analyzed for fatty acid content and profile using established methods (Kraft et al., 2003). Total fatty acid profile will be determined by gas liquid chromatography (GLC) with flame ionization detection in combination with GLC-mass spectrometry in electron ionization mode. β-carotene will be determined via solvent extraction followed by ultra-high performance liquid chromatography-photodiode array detection according to the method by Chauveau-Duriot et al. (2010).