Performing Department
Agronomy
Non Technical Summary
Alfalfa (Medicago sativa L.) is the most common and important forage crop grown across the U.S. The value of this alfalfa forage crop exceeds $9.5 billion U.S. dollars, and the domestic dairy market is the largest single outlet for this crop. Alfalfa produces high DM yield as maturity increases, but nutritive value decreases, particularly after blossoming. In other words, fiber components such as hemicellulose, cellulose, and lignin increase as stage of maturity proceeds, which lowers digestibility. Although lignin is an important component for plant rigidity, it also has particularly negative effects on digestibility. High quality forages are especially critical in dairy production because of the tenuous balance between the dramatic nutrient requirements of modern dairy cows and their need for forage fiber to maintain rumen health. Harvesting alfalfa at the optimum stage (such as late bud to early bloom) has become common practice among alfalfa grower targeting the dairy market in the U.S. Thus, if alfalfa producers miss the optimum stage of maturity in harvesting alfalfa, nutritive values of alfalfa can be negatively affected, often resulting in the need to market hay for less demanding species, at a lower price.To deal with this inverse relationship between forage yield and quality with stage of maturity, reduced-lignin and more digestible alfalfa varieties have been developed. The use of alfalfa varieties with improved nutritive value has some potential to be beneficial to alfalfa growers. For example, reduced-lignin alfalfa potentially can achieve higher DM yields by delaying alfalfa harvest while still maintaining higher nutritive values. This could allow for a wider optimal harvest window, providing growers management flexibility to delay harvest to a later stage of maturity. Currently, reduced-lignin alfalfa varieties are commercially available, but only one peer-reviewed paper has been published, focusing on forage agronomy and laboratory-estimated nutritive value of reduced-lignin alfalfa. Many producers thus rely on "guess work" to determine the optimum time of first harvest for these new varieties. In general, dry matter yields of alfalfa from first harvest represent 1/2 to 2/3 of total annual yields. However, no data is available on how the first cutting date affects DM yield and forage quality during the rest of the growing season for reduced-lignin alfalfa varieties as compared to commercial alfalfa varieties. In addition, the agronomic and the quality performance of the popular alfalfa varieties in KS and NE and more importantly the low lignin alfalfa under different water-deficit conditions under field conditions is unknown. Globally, there has been just one study so far quantifying water-deficit stress response in alfalfa from China , hence indicating the large knowledge gap that exists in our understanding the responses alfalfa varieties of local and national interest. Similarly, estimating whole plot water use efficiency through a powerful carbon isotope discrimination approach has not been determined for environments that alfalfa is grown in the U.S. Results from the proposed research objectives will be used to inform farmers' decisions on first cutting of alfalfa; in particular, how late reduced-lignin alfalfa can be harvested after blossoming compared to other conventional alfalfa varieties under different water-deficit stress scenarios. In particular, we will conducting the very first in-depth physiological and agronomic research using rain-out shelters exposed to a wide range of water-deficit stress conditions during different stages of maturity. The information generated will provide useful information on alfalfa water use information to optimize cutting strategies. Tradeoffs between DM yield and nutritive value will also be studied, including how much these tradeoffs are altered in reduced-lignin alfalfa versus conventional alfalfa varieties in different stages of maturity under different water-deficit conditions.To an even greater extent, dairy nutritionists are forced to extrapolate and guess about the appropriate feeding strategies for reduced-lignin alfalfa varieties. Often, nutritionists make assumptions about responses to these new forages based on responses to high-NDFD corn silage. However, this is a flawed approach because these are extremely different forage types, particularly when comparing corn silage to dry alfalfa hay. The impact of reduced-lignin alfalfa on dairy cattle need to be tested systematically, rather than guessing, which almost always leads to inconsistencies and lowers farmer income.Our proposal is accompanied by several letters of support that point to the need that has been communicated to us by our industry colleagues. There is a real and urgent need to address practical questions about reduced-lignin alfalfa management and feeding strategies before these traits can offer their full advantages throughout the alfalfa value chain. After successful completion of this project, we anticipate a growing acceptance of a more modern forage evaluation index (RFQ or "Eureka"), the emergence of a price differential for high-NDFD alfalfa, and substantially greater economic and management incentives for adoption of alfalfa with improved digestibility traits. Ultimately, these changes will not only improve the bottom line for alfalfa growers and dairies, but will improve the sustainability of U.S. agriculture since less land will be devoted to growing alfalfa that simply goes through dairy cows undigested.Our research team is particularly well suited to this project and its joint research and extension goals. Our institutions straddle the border between the eastern and western dairy industries, and all three investigators routinely speak at forage and dairy industry conferences throughout the U.S. and world-wide. Kononoff (UNL) is currently serving on the committee that is revising the National Research Council's Nutrient Requirements of Dairy Cattle, which is the go-to resource for feeding dairy cattle in the U.S. Collectively, we have the research experience and industry network to help address this significant gap in knowledge and begin to resolve a market inefficiency.The basic methods and approaches to collect and produce data/results will be implemented by conducting agronomic research by growing different alfalfa varieties in the field, lab analysis for forage quality, and dairy feeding trials using low lignin alfalfa varieties and other conventional varieties. During a research period, we will have field days to invite alfalfa producers, dairy farmers, and ag-industry people to explain the research trials in both Kansas and Nebraska. Our team also is going to develop Extension Factsheets, videos, and on-demand website as anextension educational resource for alfalfa producers, dairy farmers, and ag-industry people.Ultimate goals to achieve from this project:1) assesing water use efficiency of reduced lignin alfalfa compared to conventional varieties2) determinig precise information on milk yield and feed efficiency responses of highly-productive dairy cattle fed reduced-lignin alfalfa3) determinig economic impacts of feeding highly digestible alfalfa such as reduced lignin alfalfa4) making wider adoption of changes in forage analysis and valuation in alfalfaGeneral impact expected to be if this goal is met:1) Better management practices of growing reduced alignin alfalfa with more flexible harvesting schedule while maintaining high forage quality2) A growing acceptance of more modern forage evaluation index such as relative forage quality (RFQ) in the hay marketplace3) Emergence of a price differential for highly digestible alfalfaSocietal benefits being realized1) greater economic and management incentives for adoption of alfalfa with flexible harvesting window and improved digestibility traits2) improvement of sustainability of alfalfa-based dairy production systems
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Alfalfa (Medicago sativa L.) is the most common and important forage crop grown across the U.S. The value of this alfalfa forage crop exceeds $9.5 billion U.S. dollars (USDA-NASS, 2019), and the domestic dairy market is the largest single outlet for this crop (Putnam et al, 2001). Alfalfa produces high DM yield as maturity increases, but nutritive value decreases, particularly after blossoming. In other words, fiber components such as hemicellulose, cellulose, and lignin increase as stage of maturity proceeds, which lowers digestibility (Albrecht et al., 1987; Jung et al., 1997a, 1997b; Sewalt et al, 1997; Casler et al., 2002). Although lignin is an important component for plant rigidity, it also has particularly negative effects on digestibility. High quality forages are especially critical in dairy production because of the tenuous balance between the dramatic nutrient requirements of modern dairy cows and their need for forage fiber to maintain rumen health. Harvesting alfalfa at the optimum stage (such as late bud to early bloom) has become common practice among alfalfa grower targeting the dairy market in the U.S. Thus, if alfalfa producers miss the optimum stage of maturity in harvesting alfalfa, nutritive values of alfalfa can be negatively affected, often resulting in the need to market hay for less demanding species, at a lower price.To deal with this inverse relationship between forage yield and quality with stage of maturity, reduced-lignin and more digestible alfalfa varieties have been developed. The use of alfalfa varieties with improved nutritive value has some potential to be beneficial to alfalfa growers. For example, reduced-lignin alfalfa potentially can achieve higher DM yields by delaying alfalfa harvest while still maintaining higher nutritive values. This could allow for a wider optimal harvest window, providing growers management flexibility to delay harvest to a later stage of maturity. Currently, reduced-lignin alfalfa varieties are commercially available, but only one peer-reviewed paper has been published (Grev et al., 2017), focusing on forage agronomy and laboratory-estimated nutritive value of reduced-lignin alfalfa. Many producers thus rely on "guess work" to determine the optimum time of first harvest for these new varieties. In general, dry matter yields of alfalfa from first harvest represent 1/2 to 2/3 of total annual yields. However, no data is available on how the first cutting date affects DM yield and forage quality during the rest of the growing season for reduced-lignin alfalfa varieties as compared to commercial alfalfa varieties. In addition, the agronomic and the quality performance of the popular alfalfa varieties in KS and NE and more importantly the low lignin alfalfa under different water-deficit conditions under field conditions is unknown. Globally, there has been just one study so far quantifying water-deficit stress response in alfalfa from China (Liu et al., 2018), hence indicating the large knowledge gap that exists in our understanding the responses alfalfa varieties of local and national interest. Similarly, estimating whole plot water use efficiency through a powerful carbon isotope discrimination approach has not been determined for environments that alfalfa is grown in the U.S. Results from the proposed research objectives will be used to inform farmers' decisions on first cutting of alfalfa; in particular, how late reduced-lignin alfalfa can be harvested after blossoming compared to other conventional alfalfa varieties under different water-deficit stress scenarios. In particular, we will conducting the very first in-depth physiological and agronomic research using rain-out shelters exposed to a wide range of water-deficit stress conditions during different stages of maturity. The information generated will provide useful information on alfalfa water use information to optimize cutting strategies. Tradeoffs between DM yield and nutritive value will also be studied, including how much these tradeoffs are altered in reduced-lignin alfalfa versus conventional alfalfa varieties in different stages of maturity under different water-deficit conditions.To an even greater extent, dairy nutritionists are forced to extrapolate and guess about the appropriate feeding strategies for reduced-lignin alfalfa varieties. Often, nutritionists make assumptions about responses to these new forages based on responses to high-NDFD corn silage. However, this is a flawed approach because these are extremely different forage types, particularly when comparing corn silage to dry alfalfa hay. The impact of reduced-lignin alfalfa on dairy cattle need to be tested systematically, rather than guessing, which almost always leads to inconsistencies and lowers farmer income.Our proposal is accompanied by several letters of support that point to the need that has been communicated to us by our industry colleagues. There is a real and urgent need to address practical questions about reduced-lignin alfalfa management and feeding strategies before these traits can offer their full advantages throughout the alfalfa value chain. After successful completion of this project, we anticipate a growing acceptance of a more modern forage evaluation index (RFQ or "Eureka"), the emergence of a price differential for high-NDFD alfalfa, and substantially greater economic and management incentives for adoption of alfalfa with improved digestibility traits. Ultimately, these changes will not only improve the bottom line for alfalfa growers and dairies, but will improve the sustainability of U.S. agriculture since less land will be devoted to growing alfalfa that simply goes through dairy cows undigested.Our research team is particularly well suited to this project and its joint research and extension goals. Our institutions straddle the border between the eastern and western dairy industries, and all three investigators routinely speak at forage and dairy industry conferences throughout the U.S. and world-wide. Kononoff (UNL) is currently serving on the committee that is revising the National Research Council's Nutrient Requirements of Dairy Cattle, which is the go-to resource for feeding dairy cattle in the U.S. Collectively, we have the research experience and industry network to help address this significant gap in knowledge and begin to resolve a market inefficiency.OBJECTIVES1. Physiological and agronomic characterization of field-grown alfalfa cultivars exposed to a range of water-deficit stress conditions under different stages of maturity. 2. Determine impacts of alfalfa hay varying in NDF digestibility on productivity and energetics of lactating dairy cows.3. Develop and disseminate programing for alfalfa producers, dairy nutritionists, and dairy producers that seeks to achieve a better understanding of analytical-based valuations of alfalfa, enhanced production of high quality forages and overall farm profitability.
Project Methods
1) An agronomic field experiment will be conducted at the KSU North Agronomy Farm (39.2181° N, 96.5907° W) in Manhattan, KS. Six different alfalfa varieties (2 most popular varieties in KS: AmeriStand455TQRR and Gunner, 2 most popular varieties in NE: HybriForce-3400 and AFX469, and 2 reduced lignin varieties: HVXMegaTron and HVXHarvaTron) will be used for small plot agronomic field research under a rain-out shelter facility (Fig. 6a). A recommended seeding rate of 22.4 kg pure live seed per hectare will be used. The study will be planted in late summer or early fall of 2019 using a commercial grade planter with a recommended spacing (e.g., rows 7 inches apart). Before planting alfalfa, soil samples will be taken for basic analysis at the KSU Soil Testing Lab. Individual plot size will be 6.0 ft (1.8 m) × 20.0 ft (6.0 m). With 1,200 ft2 (111 m2) planting area in each of the rain-out shelter, we will be able to accommodate six large blocks one for each of the six varieties, in a rain-out shelter. Alfalfa forage samples will be collected to assess alfalfa yield and nutritive values respond in different stages of maturity (i.e., early bud, early bloom, and 7 days after early bloom) under 3 different water treatments (rainfed, irrigated, water-deficit stress using rain shelters). The irrigated plots will be watered regularly to ensure no water limitation throughout the experiment, while the rainfed plots will be maintained naturally, similar to growers field conditions. Stress in the rain-out shelters will be initiated about 5 days before the early-bud stage (previous information collected on these lines will be used to make a calculated estimate on the early bud stage). Before harvesting all 6 varieteis across all replicates and all three treatments will be measured using (i) portable photosynthesis system (LI-6400 XT, LI-COR) to calculate the instantaneous water use efficiency i.e., A(assimilation)/gs(stomatal conductance) and the photosynthetic rate; (2) Chloroplyll content using SPAD to determine changes in chlorophyll index (Bergkamp et al., 2018). Both these key physiological measurements will be collected from 09:30 AM to 11:30 AM following Sunoj et al., 2017, Sun et al., 2018. In addition, before harvesting the plot, the top most set of leaves will be sampled and the wet and dry weight will be recorded to determine the leaf moisture content. In addition, these collected leaves will be ground to capture the signature of the water-deficit stress using carbon isotope discrimination (CID), which is a powerful surrogate to estimate time integrated measure of whole plant/plot water-use-efficiency in C3 crops (Moghaddam et al., 2013; Zhu et al., 2019). CID will be measured over three different developmental stages (early bud, early bloom and 7 days after early bloom) experiencing varying levels of water-deficit stress in the six different alfalfa varieties will provide extensive knowledge on the alfalfa water-use-efficiency under varying conditions where alfalfa is currently grown in the Plains and the regions of the U.S. Nutritive values of alfalfa including crude protein, sugar, ash, acid detergent fiber, lignin, NDF, ash-free NDF, and NDF digestibility will be measured from each cutting during production years of 2020 and 2021, respectively.?2)Sixty lactating Holstein dairy cows will be used in a randomized complete block design study with a covariate period. Cows in early to mid-lactation (40 to 100 days in milk) from the Kansas State University Dairy Teaching and Research Center will first be acclimated to tie stalls and the CON diet during a 14-day covariate period. Cows will be fed total mixed rations twice per day, offering 110% of expected feed intake to ensure ad libitum access to feed. Water will be available free choice at all times. Cows will be milked 3 times daily in a milking parlor with automatic milk weight and sample collection equipment. During the last 4 days of the covariate period, milk samples will be collected for analysis of milk components (fat, protein, lactose). These methods are routine for co-PI Bradford (e.g., Olagaray et al., 2018).At the end of the covariate period, milk yield on CON diet during the 4-day collection period will be used along with parity and stage of lactation to block cows (n = 3 similar cows per block). Treatments will then be randomly assigned within block (n = 20/treatment).Cows will be fed their assigned treatment diets for 6 weeks, and management will continue as described for the covariate period. Milk yield and feed intake data will be collected daily throughout the study, and milk samples will be collected at all 3 milkings on one day/week for analysis of milk components. Yields of all milk components will be analyzed, but milk fat yield will be of particular interest as an indirect marker of adequate physically-effective fiber concentrations in diets.3)Twelve multiparous lactating Jersey dairy cows will be used. All cows will be housed in a temperature-controlled barn at the Dairy Metabolism Facility at the Animal Science Complex at the UNL (Lincoln, NE) and milked twice daily in individual tie stalls equipped with rubber mats. All animal care and experimental procedures will be approved by the UNL Animal Care and Use Committee. At the conclusion of the last experimental period, all cows will be less than 90 d pregnant and as a result, energy committed to fetal development will be minimal. The experimental design will be a three times replicated 3 × 3 Latin square. Cows will be randomly assigned to 1 of the 3 dietary treatments according to Kononoff and Hanford (2006).Animals will be blocked into each square by milk production and days in milk. Treatments will be alternated over 3 experimental periods and measurements will be collected on each animal consuming each dietary treatment. The study will be conducted with a total of 3 experimental periods, each being 28-d in duration. Each period included 21-d for ab libitum diet adaptation, targeting approximately 5% feed refusal during that time, followed by 4-d of collection with 95 % ad libitum feeding to reduce the amount of refusals. All dietary treatments will contain corn silage, alfalfa hay, brome hay, and a concentrate mixture that will be combined as a total mixed ration (TMR).