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United States Department of Agriculture

Agricultural Research Service

2013 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.

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:
This is the final report for project 3655-21000-047-00D, which terminated in January 2013. Progress was made toward development of a new meadow fescue cultivar and new sparse-flowering orchardgrass populations, including documentation of their agronomic value. Research additionally demonstrated that genetics and breeding did not play any role in the increased aggressiveness and invasiveness of reed canarygrass to sensitive wetland areas during the 20th century. Research also demonstrated that hybrid cultivars appear to be an effective mechanism to break the positive genetic correlation between forage yield and fiber concentration, allowing development of cultivars with high yield and low fiber. Grazing research found that post-grazing grass height and the timing of grazing events during the growing season have a significant impact on subsequent grass growth and long-term productivity and persistence. Various cool-season grasses were compared for nutritional value at various cutting and maturities, and meadow fescue was superior to the others. Studies identified plant expression of polyphenols, conditioning by maceration, and conservation as hay as three effective means for modulating excessive ruminal proteolysis of forage protein; shortcomings of current methods for characterizing polyphenol effects on protein degradability were also identified. Research identified a modified cutting schedule that desirably increased rumen degradable protein concentrations in red clover. In other studies, prohexadione-Ca was identified as an effective growth regulator for improving the establishment and subsequent yield of alfalfa interseeded into corn. Ensiling of fresh alfalfa leaves was investigated and was successful without amendments if the leaves were greater than 23% dry matter. Research trials demonstrated that eastern gamagrass (a perennial warm-season grass) can survive winter conditions in Wisconsin and can be used successfully to reduce voluntary intake and the energy density of diets for replacement dairy heifers. The potential for fall-grown oat forages to be used within dairy production systems was demonstrated in field trials in which these forages exhibited stable energy densities throughout the fall and a strong capacity to accumulate sugars via the winter hardening process. Work with large hay bales clearly showed that large hay packages are particularly prone to heat spontaneously, resulting in significant losses in energy in addition to reduced protein availability.

1. Condensed tannins reduce ruminal protein degradation. Although alfalfa and other legumes are known for their high crude protein concentrations, this valuable nutritional resource is often utilized inefficiently by dairy cows. Condensed tannins, which are found naturally in birdsfoot trefoil but not in alfalfa, may improve the efficiency of protein use by partially shifting the digestion of protein from the rumen to the gastrointestional tract of cattle. ARS researchers at Marshfield and Madison, Wisconsin evaluated 24 alfalfa and birdsfoot trefoil hays and silages in order to estimate the amount of protein degradation in the rumen. Protein degradation decreased by 3.2 to 4.6 percentage units of crude protein for each percentage unit of condensed tannin in the forage. Within the limits of this experiment, condensed tannins modestly reduced the proportion of protein degraded in the rumen, and this should improve protein-use efficiency of dairy cattle. Gains in protein use-efficiency are desirable because it reduces both the need for feeding costly protein supplements to cows and the loss of ammonia from manure that causes pollution of waterways and respiratory problems in humans and livestock.

2. Improved reed canarygrass cultivars and hybrids are not responsible for invasive properties of the species. During the 20th century, reed canarygrass became classified as an aggressive invader of sensitive wetland areas throughout temperate North America. This has caused many in the ecological community to call for a ban on breeding new cultivars of this species. ARS researchers at Madison, Wisconsin conducted agronomic evaluations to show that bred cultivars and hybrids that were developed for grazing livestock were no more aggressive than wild accessions, indicating that forage breeding and hybridization were not responsible for the aggressive and invasive properties of this species. This research demonstrated that the invasiveness of this species was not caused by breeding new cultivars, so attempts to ban reed canarygrass breeding will have no impact on wetland invasiveness.

3. Sparse-flowering orchardgrass has potential to simplify spring grazing management. Orchardgrass is a critically important grass in management-intensive rotational grazing systems in temperate regions of the USA. However, early and excessive flowering creates management issues by reducing acceptability and intake of forage to grazing livestock. ARS researchers at Madison, Wisconsin led efforts to show that recently developed sparse-flowering orchardgrass varieties have 57% fewer flowers compared to normal-flowering varieties. This difference was stable across 21 locations in temperate North America indicating that this trait is highly repeatable and predictable. The reduction in flowering was associated with a 25% reduction in first-harvest yield, but a 3% increase in most forage quality traits. The use of sparse-flowering orchardgrass varieties may be an effective mechanism to increase intake and simplify spring grazing management for some management-intensive rotational grazing systems in temperate regions of the USA.

4. Relationships between rain damage and alfalfa ensilability. The frustrations associated with conserving high-quality alfalfa silage during periods of unstable or inclement weather are widely known among producers. Farmers often have to choose between cutting alfalfa knowing forage quality will be reduced by subsequent rain, or waiting for the rain to pass knowing that forage quality will be reduced by advanced maturity in the crop. ARS researchers at Marshfield and Madison, Wisconsin determined that the probability of successfully preserving alfalfa in a silo (ensilability) should be affected only minimally by single rainfall events applied to relatively wet forages, as long as these events are followed by rapid dehydration to moisture concentrations suitable for making silage. However, attaining acceptable silage fermentation with forages subjected to prolonged exposure under less than ideal drying conditions is likely to be far more problematic. These results will help farmers make better harvesting decisions when trying to make alfalfa silage under rainy conditions.

5. Grazing intensity and timing impact pasture production. Inappropriate grazing management reduces the productivity, sustainability, and profitability of cool-season, pasture-based livestock farms. ARS researchers at Madison, Wisconsin demonstrated that maintaining an adequate residual grass height after grazing increases pasture productivity and increases the probability of plant survival. Management guidelines developed from this research will improve the reliability of pasture production and improve profitability by reducing the need to feed conserved forages because pasture forage is inadequate.

Review Publications
Olmstead, J., Casler, M.D., Brummer, E. 2013. Genetic variability for biofuel traits in a circumglobal reed canarygrass collection. Crop Science. 53(2), 524-531.

Price, D., Casler, M.D. 2012. Simple regression models as a threshold for selecting AFLP loci with reduced error rates. BMC Bioinformatics. 13(1):268.

Jakubowski, A., Casler, M.D., Jackson, R. 2013. Genetic evidence suggests a widespread distribution of native North American populations of reed canarygrass. Biological Invasions. 15:261-268.

Coblentz, W.K., Grabber, J.H. 2013. In situ protein degradation of alfalfa and birdsfoot trefoil hays and silages as influenced by condensed tannin concentration. Journal of Dairy Science. 96:3120-3137.

Coblentz, W.K., Muck, R.E. 2012. Effects of natural and simulated rainfall on indicators of ensilability and nutritive value for wilting alfalfa forages sampled before preservation as silage. Journal of Dairy Science. 95:6635-6653.

Coblentz, W.K., Hoffman, P.C., Esser, N.M., Bertram, M.G. 2012. Using eastern gamagrass to construct diets that limit intake and caloric density for dairy replacement heifers. Journal of Dairy Science. 95:6057-6071.

Coffey, K.P., Montgomery, T., Coblentz, W.K., Francis, P.B., Whitworth, W.A., Bryant, K.J. 2013. Performance by heifers grazing sod-seeded cool-season annuals seeded on different dates using two tillage intensities. Forage and Grazinglands. DOI: 10.1094/FG-2013-0226-01-RS.

Mays, A.R., Looper, M.L., Williamson, B.C., Coffey, K.P., Coblentz, W.K., Aiken, G.E., Rosenkrans, C.F. 2013. Forage and breed effects on behavior and temperament of pregnant beef heifers. Journal of Animal Science and Biotechnology. 4:20. DOI:10.1186/2049-1891-4-20.

Lopes, F., Coblentz, W.K., Hoffman, P.C., Combs, D.K. 2013. Assessment of heifer grazing experience on short-term adaptation to pasture and performance as lactating cows. Journal of Dairy Science. 96:3138-3152.

Last Modified: 8/1/2014
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