Location: Dairy Forage Research2010 Annual Report
1a. Objectives (from AD-416)
Objective 1: Overcome the production and profitability problems suffered in grazing-based systems because of poor plant persistence, inconsistent forage quality, and lack of resilience/stability. Objective 2: Develop new alfalfa (Medicago sativa L.) production systems that are less costly, more productive, and of greater value for livestock and biomass conversion. Objective 3: Develop improved understanding of the fundamental physiological, anatomical, and genetic controls that affect forage quality during plant development and digestion in the rumen. Objective 4: Broaden the range of alternative forage cropping systems to fulfill dietary needs, reduce environmental risk, and improve management flexibility. Objective 5: Develop and evaluate new forage materials to improve animal productivity, grazing options and bioconversion efficiency for biofuels, and bioproducts. Objective 6: Develop specialty forages and management practices for multiuse buffer strips to more effectively meet IEIDM objectives. Objective 7: Develop management practices and systems for growing companion crops with primary bioenergy crops to enhance flexibility, profitability and sustainability (e.g., alfalfa in rotations with corn).
1b. Approach (from AD-416)
We propose to develop new and more efficient management strategies and new forage cultivars, focused on four basic research themes related to forage plants and systems: (1) grass-based management-intensive rotational grazing systems, (2) harvested alfalfa as a bioenergy feedstock or livestock feed, (3) selection criteria for improving forage quality of pastures and harvested forages, and (4) alternative establishment methods and forage cropping systems. Hypothesis-driven research will be conducted largely with field trials designed to test new or improved cropping systems, management strategies, establishment methods, or germplasms in direct comparison to current or existing treatments. Field studies will be supplemented with laboratory analyses of forage characteristics related to nutritional value, plant cell walls, physical traits of stems and leaves, or DNA markers to identify functional relationships of field observations with expected ruminal livestock performance, further supplemented with animal evaluations in some cases. New forage cultivars and management strategies will be used to streamline forage production systems, increasing profitability and sustainability, while lessening environmental impact. We will publish numerous scientific articles that will add significant new findings to the scientific literature and will disseminate our findings to stakeholders in the agricultural community via a wide range of outreach programs and methods.
3. Progress Report
Harvesting was completed on existing field experiments of orchardgrass, smooth bromegrass, timothy, and reed canarygrass. New field experiments were established for meadow fescue, orchardgrass, meadow bromegrass, timothy, and reed canarygrass. We completed data collection from field and greenhouse studies of pasture grass response to grazing management variables, and analysis of samples from pasture utilization studies. Field sites were identified and prepared for implementing new harvest and storage-management studies. Progress was made toward enhancing our knowledge of sub-optimal harvest and storage of dairy-quality forages. Harvesting was completed for field experiments of eastern gamagrass and fall-grown, cereal-grain forages. Extensive summaries of data for outdoor storage of hay in northern environments, as well as the consequences of spontaneous heating in large hay bales, were completed and published in refereed journals. We assessed the utility of various methods for estimating rumen degradable protein (RDP) in conserved forage legumes containing protein-protecting polyphenols and found that conventional in situ kinetic estimates could be accurately predicted by some but not all alternative methods. Such cross-validation combined with further refinement of RDP methods will facilitate the development and efficient utilization of new forage germplasm by ruminant livestock. In other studies, preliminary data suggest yield of biomass alfalfa could be substantially increased by drill-seeding plants in a 4 x 4 cm grid vs. conventional rows spaced 15 cm apart. Other work indicates spray applications of phytohormone inhibitors can improve alfalfa establishment in corn with only modest reductions in corn yield, but additional work is needed to improve growth regulator efficacy for maximizing yields and minimizing nitrogen fertilizer inputs of corn and alfalfa grown in short term rotations. Analyses of alfalfa leaf and alfalfa stem silages made in 2008 and 2009 with various treatments were completed. The stems ensiled well with or without treatment. Success of direct ensiling alfalfa leaves depended on their dry matter content. In summer 2010, alfalfa leaves harvested with a prototype harvester were ensiled in a bag silo with and without treatment.
1. North American reed canarygrass cultivars are almost exclusively of European origin. DNA marker and sequence analysis has identified three distinct European lineages of reed canarygrass: Scandinavian, Continental European, and Iberian. All bred cultivars in the USA and Canada trace to one or more of these lineages, which were introduced to North America to fuel the significant interest in this species between 1880 and 1940. Initial results from samples collected across central and northeastern USA suggest that most common reed canarygrass along roadsides, riparian zones, wetlands, and other habitats derives from one or more of these European lineages. These results are significant to ecologists, restorationists, conservationists, and land managers, because they indicate the most reed canarygrass that has colonized fragile and/or invasible habitats is not of direct or recent North American origin, i.e. it is not native.
2. Documented and developed a new pasture species for humid, cool-season regions of the USA. ARS scientists, in collaboration with the University of Wisconsin, have documented naturalized meadow fescue populations that originate from early immigrants to the Driftless Region of the Upper Mississippi River Basin. Meadow fescue has been documented on hundreds of farms in the region and agronomic trials have demonstrated extremely high forage quality and pasture suitability relative to other species, including evaluations on several farms and experiment stations. One new cultivar has been developed from this germplasm and others are currently in the development pipeline. Graziers and extension personnel have benefited from this research by an increased knowledge of how to optimize management of meadow fescue and by increased access to existing meadow fescue cultivars. The grass seed industry has benefited by a significantly increased demand for meadow fescue seed.
3. Grazing management influences pasture yield distribution and persistence. A primary consideration for pasture-based producers is how the frequency and extent of grazing influences annual pasture productivity, seasonal yield distribution, and grass persistence. ARS researchers at Madison, WI determined that although annual yield was initially increased by grazing a greater proportion of pasture growth, grass growth rate between grazing events and grass plant persistence were significantly reduced, resulting in a long-term loss of above- and below-ground productivity. These studies provide pasture-based livestock producers with straightforward management guidelines to maintain pasture productivity and nutritive value, and the short- and long-term consequences of specific grazing practices.
4. Beef and dairy producers in the U.S. often use fall-seeded small-grain crops as a source of high-quality forage. This practice is common with hard-red winter wheat in the Southern Great Plains. However, producers in other regions of the country potentially could make better use of these cereal-grain forages, especially in the fall. This management approach could be used to extend the grazing season or provide a one-time harvest of emergency silage following summer drought. We conducted a study to assess the fall-growth potential of wheat, triticale, and oat cultivars in Wisconsin, and also the quality (fiber composition and energy density) of these forages. Evaluated at 3-week intervals between 15 September and 1 November, yields of dry matter increased over time for all cultivars, but accumulation rates were faster during late September and early October compared to late October. Cultivars that exhibited stem elongation (oat and triticale) out-yielded wheat, which remained vegetative, by a 2:1 margin. Despite advancing tiller development and increased yields, the energy density of oat and triticale forages remained relatively stable across harvest dates. This study shows producers that they can time the harvest of fall-grown cereal grains to maximize yield, or on the basis of convenience, without sacrificing available energy.
5. Spontaneous heating in hay, generally caused by too much moisture in the plant at the time of baling, costs livestock producers in terms of dry matter losses (less hay to feed) and forage quality. Most livestock producers and nutritionists are familiar with how protein is damaged or lost when bales experience spontaneous heating; generally this occurs through formation of indigestible complexes of forage proteins and carbohydrates. However, bale packages today are generally larger and more susceptible to spontaneous heating than they were a generation ago, and concepts describing heat damage to forage proteins have not been evaluated thoroughly within this context. For this project, estimates of ruminal protein degradation rate and effective ruminal degradability (digestibility) declined sharply in close association with measures of spontaneous heating when heating was limited within large hay packages, which is consistent with past work. However, these expected trends did not continue within bales that heated excessively and sometimes exhibited visible charring. It remains unclear whether these unexpected responses could be demonstrated with other analytical techniques, or whether the severity of these heating increments exceeded the reliable limits for estimating protein degradability via in situ methodology. This research will aid nutritionists in the evaluation and appropriate use of heat-damaged hays for dairy cows and replacement heifers.
6. Due to greater ease of harvest and transportation, large-round and large-square hay bales are being used more extensively now than hay packaged in conventional (100-pound) bales. However, these larger bales are more likely to heat spontaneously than conventional bales during storage, and much of the feed value is lost when the hay is heated. In severely heated hays from large-round bales, estimates of the energy available in the hay, expressed as total digestible nutrients (TDN, a common energy estimate), declined by as much as 13.0 percentage units during storage. Greater estimates of TDN were obtained when the product of protein-corrected neutral detergent fiber (NDF) and 48-h NDF digestibility were used to estimate truly digestible fiber (part of the TDN estimate) compared to the alternative acid-detergent lignin option. Discrepancies between these estimates also were made worse when NDF rather than protein-corrected NDF was used to estimate truly digestible fiber. As such, any use of the 48-h NDF digestibility option for determining truly digestible fiber, and subsequently TDN, should utilize protein-corrected NDF if there is any other evidence suggesting that hays were heated during storage. This information will help dairy nutritionists to better balance diets for dairy cows and heifers, and to properly discount the energy content of heated hays.
7. In situ kinetic vs. alternative methods for estimating rumen degradable protein (RDP) in forage legumes. Our objective was to assess the utility of various methods for estimating RDP in conserved forage legumes containing protein-protecting polyphenols such as condensed tannins or o-quinones. Such cross-validation will insure that RDP in forage legumes can be routinely and properly characterized for feeding to ruminant livestock or for the development of improved plant germplasm. In this study, RDP in rolled or macerated silages and hays of Medicago sativa (L.), Lotus corniculatus (L.) and Trifolium pratense (L.) with differing polyphenol makeups were estimated by a standard in situ kinetic method, a 10-h in situ incubation, Cornell Net Carbohydrate and Protein System fractions, a rumen microbial inhibitor in vitro assay, or a high throughput 16 h in vitro Streptomyces protease digestion. Forage type, conditioning and conservation methods influenced RDP estimates. In situ RDP could be ranked or in some cases accurately predicted by other RDP methods, but the protease method must be refined to provide nutritionally meaningful RDP estimates for diverse types of conserved forage legumes.
8. Separate ensiling of alfalfa leaves and stems. In order to obtain high quality alfalfa to support high milk production levels, producers are cutting alfalfa earlier and more often. Unfortunately, this raises production costs and shortens the life of alfalfa stands. An alternative may be to harvest leaves and stems separately because leaves have much higher quality than stems and leaf quality declines little as the plant matures. A prototype harvester directly removed alfalfa leaves from the plant and cut the stems to dry in the field. We ensiled the leaves and stems separately without treatment or with an inoculant, cell-wall degrading enzyme or formic acid. The stems when wilted to 65% moisture ensiled well with or without treatment. The leaves ensiled well when at 77% moisture, but underwent a bad fermentation when ensiled at 83% moisture no matter what treatment was used. This could be avoided by modest decreases in moisture content through the addition of a drier crop or by increasing formic acid addition over that tested. Overall, these results show that separate harvesting of alfalfa leaves and stems may be a promising future technology for producers, reducing production costs and providing more flexibility in harvest windows and utilization of alfalfa.
5. Significant Activities that Support Special Target Populations
Scientists have participated in activities targeting small farmers with size-neutral technologies such as new forage species, improved cultivars, improved harvest and storage systems, and improved management systems for rotational grazing systems in the northern USA.