1a. Objectives (from AD-416)
1.A. Develop tools to facilitate the selection of species mixtures for pastures, the distribution of pasture types across a farm, and the assessment and monitoring of pastures at multiple scales to improve forage/grassland system function and reduce production risks. 1.B. Identify new grazing management and supplementation strategies that complement grazing preferences of dairy cattle to optimize the utilization of mixed-species cool-season pastures of the Northeast U.S. and to reduce inputs costs for pasture-based producers. 2.A. Identify management systems that minimize net greenhouse emissions in forage, grassland, and energy crop systems in humid-temperate climates. 2.B. Determine optimal management and environmental benefits of perennial and annual bioenergy cropping systems in the Northeast U.S. to reduce production costs and increase yields.
1b. Approach (from AD-416)
1.A. A trait-based index will be developed to relate pasture plant community composition (both species presence and abundance) to ecosystem function in grasslands. A multi-site field-plot trial will be conducted to test the hypothesis that mixed plant communities with greater species evenness produce more herbage and are more resistant to weed invasion than mixtures with lower evenness or monocultures. Science-based decision support tools will be developed for forage species selection within pastures and across farms to meet producer goals for ecosystem functions given the climate, landscape and soils. 1.B. Observational research will be conducted on pasture-based dairy farms feeding a range of supplementation strategies with varying pasture composition to characterize the effects of supplementation on grazing behavior and diet selection. Ingestive behavior will be quantified on during spring, summer, and fall grazing. Detailed feeding and milk production information will be collected from farm records and personal interviews. Continuous culture fermenters will be used to identify ruminal fermentation products that influence grazing patterns via post-ingestive feedback mechanisms. Sward-box studies will be used to evaluate cattle grazing behavior responses to monocultures and mixtures of selected grasses and legumes. 2A. Multi-location field plot and farm-scale trials will be conducted to determine the greenhouse gas emissions and economics of perennial and annual crops grown for bioenergy. Differences in C isotope discrimination (d13C) of C3 and C4 species will be exploited to partition respiration between new C respired from C3 plants such as orchardgrass and white clover and old C respired from the active pool of soil organic matter that has formed under the C4 species, big bluestem. 2B. Biomass yield, feedstock quality, and greenhouse gas emissions of current annual and proposed perennial bioenergy crops under the same climate and soil will be measured, and the resulting data will be used to validate the DAYCENT biogeochemical model at a site in the northeastern U.S.
3. Progress Report
Progress by Subobjective: 1.A.1. The greenhouse study of above- and below-ground traits for eight plant species also used in field trials was completed. Data analysis and summary are underway. 1.A.2. Establishment of research plots at five locations was completed in spring 2009 with the final planting at Alfred State College in Alfred, NY. Harvest management and data collection are on schedule for all locations. Weed invasion tests were completed during the establishment phase and data analysis is in progress. 1.A.3. Three research tools have been developed based on mathematical functional diversity indices; the Competitive-Stress tolerator-Ruderal functional group classification system; and the Leaf-Height-Seed functional group classification system. 1.B.1. Research on how molasses supplementation affected digestion and ruminal fermentation of a pasture-based diet indicates that supplementation improves protein digestibility and does not impair digestibility of other nutrients. Molasses provides a lower-cost source of energy for pastured dairy cows without impairing ruminal function. Research on timing of corn silage supplementation in relation to the grazing period affected ruminal fermentation indicate that a simple change in timing of supplementation, 9 rather than 1 h before a grazing period, improves ruminal fermentation and digestibility and reduces the environmental impact of nitrogen losses in grazing cattle. 1.B.2. Research was completed on the influence of grass canopy structure, and herbage chemical and physical characteristics on intake, digestibility, and grazing behavior of dairy heifers. Data analysis and summary are in progress. This was a collaborative effort with the ARS Dairy Forage Research Center in Madison, WI. 2.A.1. Fall evaluation of a five-species pasture mixture that is part of the multi-location GRACEnet project indicated that chicory had disappeared from the mixture by four years after pasture establishment. Three methods were employed to re-establish chicory in the mixture, broadcast seeding in February, seeding with a no-till drill in March, and broadcast seeding just before the first grazing in May with hoof incorporation of the seed. By one month after seeding, all three methods had greater than 40 chicory seedlings per square meter. 2.A.2. A study to quantify seasonal effects on partitioning of soil respiration in heterotrophic and autotrophic components continued with respiration measurements in mid-March, May, and July. A new site was prepared for 2010 to measure respiration partitioning during the regrowth cycle following defoliation. 2.B.1. Annual and perennial crops were established at the Penn State Hawbecker farm and other management practices were completed as appropriate during growing season including biomass harvest. 2.B.2. Biomass samples were analyzed for feedstock quality and data summarized from Cycle 1 of summer, fall, and spring harvest seasons and annual, biennial, and triennial harvests of switchgrass. Cycle 2 switchgrass harvest occurred as appropriate as well as collection of ancillary data.
1. Hormones control grazing behavior in dairy cattle: Understanding the link between the motivations to eat and grazing behavior of cattle can help us optimize animal well-being and performance. We adjusted the ruminal fill in grazing cattle and measured the ensuing changes in hormone levels and grazing behavior. Cattle that were less full (less ruminal fill) had higher levels of the appetite-regulating hormones ghrelin and insulin and lower levels of glucose in their blood and took more and larger bites of forage when grazing. This research demonstrated a clear link between the endocrine physiology of grazing cattle and their grazing behavior.
2. Developed simple measures to assess grazing behavior of cattle in biodiverse pastures. Pastures containing multiple forage species have been shown to increase forage productivity compared with pastures planted with a single forage species. However, we do not know if this diversity of plants changes the grazing behavior of cattle. We tested this by offering four grass species to cattle in short-term intake trials and measuring the grazing behavior responses. Plant height had the largest and most consistent effect on cattle grazing behavior. Cattle took more and larger bites from taller plants, which suggests that simple measurements of pasture height can be used to predict grazing behavior of cattle and lead to improved management recommendations.
3. Pasture is "easier" to chew in the evening: Cud chewing is an important part of the digestion process in cattle and things that make forage difficult to chew and digest can reduce cattle performance. We designed a study to evaluate changes in the chewing characteristics (“toughness”) of pasture forage in relation to its chemical composition throughout the day. Toughness, an indirect measure of how hard forage is to chew, decreased late in the day, which corresponded with a decrease in fiber and protein, and an increase in sugar of the forage. Our results explain why cattle prefer to graze longer and more intensely in the evening and suggest that farmers should adjust their grazing management to maximize this effect to increase animal performance.
4. Fatty acid composition of pasture stable throughout the day: Fatty acids in forage influence the level of “healthy” fats in milk and meat from grazing cattle. We designed a study to determine if fatty acid composition of forage varied during the day, which could have important implications in meat and milk composition. Despite large changes in other chemical components, concentrations of fatty acids in grass forage remained stable during the day, indicating that beneficial fatty acid composition of pasture-based meat and milk products should be stable as well. Farmers who adjust their grazing management to maximize cattle grazing late in the day will not affect meat or milk composition.
5. Forage Diversity Reduces Production Risk: The use of multispecies pasture mixtures may increase yield and sustain forage production; however, we have no information on how grazing management affects the productivity of mixtures. We evaluated the effects of two grazing schedules on forage production of grass monocultures, simple grass-legume combinations, and more complex mixtures of 3 to 7 forage species under rotational grazing. Basing grazing management on plant height produced greater forage yields than grazing based on plant morphology. Mixture complexity improved forage production under drought stress and variability in forage yield decreased with increasing mixture complexity. The use of complex pasture mixtures can be a risk-management practice in drought-prone environments where consistency in forage production on pastures is more important than maximum productivity.
5. Significant Activities that Support Special Target Populations
Molasses as an Alternative Energy Supplement for Organic Dairies: High organic grain prices and low organic milk prices have caused organic dairy farmers to seek alternative feed sources, such as molasses, to reduce feed costs while maintaining milk production. We evaluated the effects of molasses supplementation on ruminal fermentation of a pasture-based diet. Molasses improved protein digestibility and did not impair digestibility of other nutrients. Molasses may provide a lower-cost source of feed energy for pastured organic dairy cows without impairing ruminal function. Seed bank Characterization of Organic Pastures and Hayfields: Buried seeds in pasture soils are often reservoirs of weedy plants. We characterized the seed bank in pastures and hayfields with different management histories at the University of New Hampshire Organic Research Dairy. Soil from hayfields had the fewest number of seed and plant species compared with pastures. Nearly 42% of the soil samples from the hay fields had no germinable seeds, whereas only 7% of soil samples from pastures had no germinable seeds. Grasses were most abundant in the pastures and grass hayfield. This new knowledge of how land-use affects the seed bank in pastures will be useful in anticipating potential weed management needs. Assessing Pasture Grasses, Legumes and Pasture Blends for Limited-Resource Farms: Many small farmers seek information and recommendations on pasture species and varieties, especially regarding commercial pasture blends or mixtures. We evaluated 25 to 30 commercial pasture mixtures from several seed companies in grazing trials on several farms in Massachusetts, Vermont, and Pennsylvania. Data analyses indicate that mixtures with 3 to 5 species yielded more forage; however, there was a large range in variation among mixtures. Our results will provide site-specific recommendations for farmers interested in using commercial mixtures of forages for pasture plantings.
Gregorini, P., Soder, K.J., Sanderson, M.A. 2008. Case Study: A Snapshot in Time of Fatty Acids Composition of Grass Herbage as Affected by Time of Day. Professional Animal Scientist. 24(6):675-680.