Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061
Performing Department
(N/A)
Non Technical Summary
The pressure to reduce GHG emissions from dairy farming systems is growing in the US. The US Dairy Net Zero Initiative is a program seeking the reduction of the environmental footprint of dairy farming systems through the reduction of enteric methane emissions from dairy cattle. Therefore, it is critical that researchers find novel nutritional strategies to reduce enteric methane emissions from dairy farming systems. Our working hypotheses are that alfalfa yields can increase in the climate change scenario through renovated variety selection and harvest regime and that feeding high-quality alfalfa to dairy cattle can reduce methane emissions through a better synchrony between the rates of ruminal fiber digestion and ruminal fiber passage. We will conduct agronomic field research experiments evaluating the impact of variety selection and harvest regime on alfalfa forage yield and quality under climate change conditions in Pennsylvania and Virginia. These agronomic experiments will provide forage samples to evaluate neutral detergent fiber (NDF) ruminal digestion kinetics. We will also conduct animal feeding trials evaluating how the forage passage rate affects enteric methane emissions from dairy cattle when feeding diets containing alfalfa as forage sources. In addition, we will conduct a comprehensive literature review and a life cycle analysis (LCA) to quantify the carbon footprint of dairy systems incorporating alfalfa relative to dairy systems based exclusively on annual crops (corn silage and cool-season cereal grasses). We will conclude this project by transferring knowledge to dairy nutritionists through a holistic Extension program. As an outcome of this project, we foresee dairy nutritionists recommending seeding more alfalfa in the US in response to the global demand for a dairy industry moving towards zero net GHG emissions.
Animal Health Component
65%
Research Effort Categories
Basic
(N/A)
Applied
65%
Developmental
35%
Goals / Objectives
1) Evaluate the impact of alfalfa dormancy and harvesting regime on biomass yield and forage quality under climate change conditions.2) Evaluate the use of alfalfa hay or haylage in diets as a means for reducing methane emissions from lactating dairy cows.3) Improve the methods of analysis to determine the ruminal degradability of NDF from alfalfa and other forages4) Conduct a life cycle analysis (LCA) of alfalfa in relation to the emissions of GHG by dairy farming systems.5) Transfer the existing and generated knowledge to stakeholders (e.g., dairy nutritionists and farmers, extension educators, and dairy industry in general) through a holistic Extension program.
Project Methods
Plot Study. We will conduct a plot study. The experimental design will be a split-plot design with four replications, with harvest timing and frequency as the whole plot and alfalfa varieties as a subplot. Alfalfa varieties from each recommended and proposed fall dormancy rating for each study site will have two selections, one from the major alfalfa seed companies. Our subplots will also include two low-lignin alfalfa varieties. The harvest timing and frequency include the traditional early-bud harvest, which is all season long, and the flexible harvest timing and frequency regime; the timing of the alfalfa harvest is when plant height reaches 24 inches or early-bud maturity stage, whichever is earlier. The regrowth of alfalfa after the penultimate cut in the early fall will be harvested after the first killing frost around the middle of October.Animal Study 1. We will feed one of two diets [high alfalfa (HA) vs. low alfalfa (LA)] to 12 first-parity Holstein cows (6 of them rumen-cannulated) according to a crossover design with two 28-day periods. Ideally, we will formulate both diets to contain ~30% NDF and ~22.5% forage NDF (DM basis) using the Cornell Net Carbohydrate and Protein System (CNCPS). Alfalfa haylage will provide ~15.0 and ~7.3% forage NDF in the HA and LA diets, respectively, and corn silage the remaining forage NDF. We will feed the cows individually using a Calan gate feeding system. We will collect dry matter intake, milk yield, and yields of milk components from all cows during days 10 to 16 of each experimental period. On days 10 to 16 of each period, we will also measure enteric methane emissions [i.e., absolute (g/day), yield (g/kg DM), and intensity (g/kg milk)] from the 6 non-cannulated cows using a GreenFeed system.From days 14 to 16 of each period, we will collect fecal grab samples from all the cows four times daily. We will composite the 12 fecal samples to represent a 24-hour collection. On days 17 and 23 of each period, we will determine the pool size of ruminal contents on the six rumen-cannulated cows. For this, we will manually evacuate the ruminal contents, separate the solid and liquid phases using a fruit squeezer, and put the ruminal contents back into the rumen after adding and mixing a pulse dose of marked fiber. We will use chlorides of lanthanum and ytterbium as external markers, and we will measure the concentration of the marker in the ruminal contents at 0, 2, 4, 8, 12, 24, 30, 36, 42, 48, 60, and 72 hours after completion of this process. To determine the rate of passage (Kp) of the fiber from the rumen, we will measure the dilution rate of the marker using non-linear analysis as previously performed by the research team.The ruminal fiber passage rate of pdNDF and uNDF will be determined using non-linear analysis of marker escape relative to NDF and uNDF. We will evaluate the effects of the diets on the variables of interest using the MIXED procedure of SAS according to a model that will include the fixed effect of diet, the random effects of period and cow, and the random residual error.Animal Study 2. After securing alfalfa (ALF) and triticale (TRI) haylages, we will feed one of two diets (ALF vs. TRI) to 12 first parity Holstein cows (6 of them rumen-cannulated) according to a crossover design with two 28-day periods. As in the animal Study 1, we will formulate both diets to contain ~30% NDF and ~22.5% forage NDF (DM basis), and both haylages will provide ~15.0 of the forage NDF and corn silage the remaining forage NDF. The rest of the experimental procedures will be as described for Animal Study 1.In Vitro Study 1. The objective of this study is to compare the in vitro ruminal NDF digestion kinetics of alfalfa forages and other fibrous ingredients using BAG and FSK methodologies. We will dry (55°C with forced-air oven) and grind (1-mm of cutter mill) a diverse set of forage and non-forage samples (alfalfa whole plants, alfalfa stems, alfalfa leaves, corn silage, and soybean hulls). For the FSK system, we will put 0.25 g of sample into a 200-mL Erlenmeyer flask sealed with a rubber stopper holding a one-way valve. For the BAG system, we will put 0.25 g of sample into F57 filter bags, and the bag will be also placed into a 200-mL Erlenmeyer flask sealed with a rubber stopper holding one-way valve. In a water bath (38°C), we will incubate each sample in 100 mL of ruminal inoculum59for 0, 3, 6, 12, 24, 48, 96, or 240 h. At the end of the incubations, we will place all flasks (both FSK and BAG) in a freezer to terminate microbial fermentation. To determine the residual NDF, we will use an Ankom200 fiber analyzer (Ankom Technology, NY) for the BAG treatment and Gooch crucibles for the FSK treatment.60We will determine the Fraction A as the proportion of NDF disappearing at 0 hour and Fraction C will be determined as the NDF residue remaining after a 240-hour fermentation. We will determine the discrete lag time deriving Y = a + b·ln(X), where Y equals 100 and represents no disappearance of NDF, b is the slope of the curve, and b is the intercept of the line. Given the size of the experiment (i.e., 5 samples ´ 2 treatments ´ 8 time points = 64 flasks per experiment), we will need to replicate each in vitro run 5 times. We will evaluate the effects of the in vitro system on the variables of interest using the MIXED procedure of SAS according to a model that will include the random effect of block or run, the fixed effects of system and sample, and the random residual error.In Vitro Study 2. We will collect whole plants of alfalfa from the plot study. These whole plants will be subjected to a dehydration process mimicking wilting in the field or to an ensiling process using plastic pouches and a vacuum sealer.After dehydrating and ensiling, we will process and determine parameters of NDF digestion kinetics as described in In Vitro Study 1.In Vitro Study 3. We will collect whole plants of alfalfa from the plot study. We will dry and grind those whole plants to pass a 2-mm screen or a 1-mm screen of a cutter mill (Willey). Then, we will determine parameters of NDF digestion kinetics as described in In Vitro Studies 1 and 2.Life Cycle Assessment. The team will conduct a literature review on alfalfa and corn silage production system environmental impacts, including soil carbon sequestration, nitrogen fertilization input or nitrogen fixation credits, CH4and N2O emissions, farming energy needs, and other carbon inputs and outputs. This team will conduct a life cycle analysis to compare the carbon footprint of alfalfa and corn silage production systems.Extension Programming. To generate a regional impact, the team will perform field days and workshops in the Mid-Atlantic area. The team will also develop promotional and educational videos that we will stream on the YouTube channel of VTDairyScience. To generate a broader impact on the dairy and forage industries, the team will write at least three popular press articles in Hoard's Dairyman or Hay & Forage Grower and popular press articles for the Dairy Intel newsletter of Hoard's Dairyman. The team will write at least two peer-reviewed Extension bulletins explaining the benefits of alfalfa as a tool for reducing methane emissions in dairy cattle. To generate impact among dairy nutritionists, the team will deliver presentations at professional conferences like the Penn State Dairy Cattle Nutrition Workshop or similar events. To reach the scientific community and policymakers, the team anticipates writing at least five manuscripts in professional journals like the Journal of Dairy Science, Agronomy Journal, or similar. To perpetuate the transfer of knowledge to stakeholders, the team will develop an e-learning platform where stakeholders will obtain information relevant to the benefits of using alfalfa in an industry moving towards zero net emissions of greenhouse gasses.