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United States Department of Agriculture

Agricultural Research Service

Research Project: Forage Characteristics that Alter Feed Utilization, Manure Characteristics and Environmental Impacts of Dairy Production

Location: Dairy Forage Research

2013 Annual Report

1a. Objectives (from AD-416):
Objective 1: Determine the effects of dietary crude protein and forage type on feed utilization by dairy cows and heifers, in-barn methane and ammonia emissions, the production and chemistry of manure, and the impacts of these outcomes on manure nutrient availability in soils. • Sub-objective 1.A. Determine the primary dietary sources of ammonia (NH3), nitrate (NO3) and nitrous oxide (N2O) losses from urine and feces produced by lactating cows fed a typical ration of alfalfa silage, corn silage, corn grain and roasted soybeans. • Sub-objective 1.B. Evaluate the effects of forage types and supplementation on lactating cow urine and feces composition and subsequent losses of N in-barn and after application to soil. • Sub-objective 1.C. Determine impacts of limit feeding and monensin on NH3, NO2, CO2, methane (CH4) emissions from replacement dairy heifers. • Sub-objective 1.D. Evaluate diet options for gravid dairy replacement heifers raised in confinement. • Sub-objective 1.E. Evaluate grazing systems for raising replacement heifers. Objective 2: Characterize polyphenol-containing plant extracts and determine how they can be used to alter dairy cattle nitrogen efficiency, reduce in-barn emissions of ammonia and greenhouse gases and modify manure nitrogen availability in the soil. • Sub-objective 2.A. Identify tannin fractions that are most effective for shifting the digestion of plant protein from the rumen to the gastrointestinal tract and for ammonia abatement in manure. • Sub-objective 2.B. Determine dietary tannin impacts on NH3 and CH4 emissions from dairy barns. • Sub-objective 2.C. Evaluate the effects of adding tannin extracts directly to free-stall barn floors on NH3 and CH4 emissions. • Sub-objective 2.D. Determine the impacts of dietary tannins on manure chemistry and soil C sequestration, soil N mineralization, crop N uptake and crop yield after application of manure to soil. Objective 3: Determine how silage feed additives alter rumen fermentation and feed utilization in dairy cattle. Objective 4: Develop techniques and technologies to better estimate the digestion and physical function of forages and other feedstuffs in the rumen and overall utilization by the cow. • Sub-objective 4.A. Evaluate the effects of forage quality on energy intake, partitioning and feed conversion efficiency. • Sub-objective 4.B. Develop a functional characterization of forage fiber, accounting for physical form, fragility and digestion characteristics. • Sub-objective 4.C. Evaluate the physiological effects of metabolic fuels on energy intake and partitioning.

1b. Approach (from AD-416):
Objective 1. Alfalfa silage, corn silage, corn grain and roasted soybeans will be 15N (Nitrogen) enriched in the field and fed separately as part of a standard ration. Urine and feces will be collected from lactating cows on these rations and used in laboratory studies to estimate ammonia emissions from barn floors and soil N transformations after manure application as influenced by each feed. Urine and feces will be collected from various lactating cow trials having treatments of different forage types and supplementation strategies to understand their effects on ammonia emission from the manure and subsequent soil N transformations after manure application. The effects of limit feeding and monensin on ammonia and greenhouse gas emissions from replacement dairy heifers will be studied in emission chambers. Feeding options for raising dairy replacement heifers in confinement and grazing settings will also be evaluated. Objective 2. The ruminal-gastrointestinal digestibility of alfalfa proteins treated with chemically defined condensed and hydrolysable tannin fractions will be determined by in vitro incubation followed by enzymatic hydrolysis. Fractions from a commercial quebracho-chestnut tannin extract responsible for urease inhibition in dairy feces will be identified. Tannin extracts will be fed to lactating dairy cows at 0 to 3% of dietary dry matter, and effects on in-barn emissions of ammonia and methane will be measured. Feces collected from this experiment will be applied to soil to measure effects on soil C (carbon) and N cycles. Adding tannin extracts to free-stall barn floors will be studied as a means of reducing in-barn ammonia and methane emissions. Objective 3. In vitro analyses of untreated, inoculated and formic acid-treated silages will be performed to understand how a Lactobacillus plantarum silage inoculant can affect rumen microbial growth. Various silage extracts will be made and added to in vitro ruminal fermentations. Inoculated silage extracts that appear to contain the factors affecting ruminal microbial growth will be compared to extracts from untreated silages using a metabolomics approach to identify chemical differences. Objective 4. A series of lactating cow trials will be performed to examine the effects of forage quality on energy intake, partitioning and feed conversion efficiency. Functional relationships between physical form, fragility and digestion characteristics of forage fiber will be developed and tested in ruminally fistulated cows. Differences in the mix of energy sources in lactating cow rations on intake and partitioning at different stages of lactation will also be measured.

3. Progress Report:
Relationships among methane emission, ammonia emission, and selected animal performance parameters were determined from three experiments comprised of 12 dietary treatments fed to lactating cows in air-flow controlled chambers. Methane emissions increased with increasing intake up to a dietary dry matter intake level of 26 kg/cow per day, and then declined within the range of 26 to 30 kg/cow per day. There were strong relationships between methane and ammonia emission. Of the total nitrogen consumed by a lactating cow, 14% is emitted as ammonia. As feed nitrogen use efficiency increases above 24%, ammonia emissions decrease. A short-term dietary experiment with cows in air emissions chambers revealed that cows having high feed conversion efficiency for milk (FCEmk) may also have low methane emissions. A longer-term trial was conducted to determine the persistency of FCEmk and possible relationships among the parameters of FCEmk, methane emissions, and digestive and metabolic functions of cows. Cows who demonstrated high FCEmk were more efficient for converting feed energy into milk, body weight gain, and maintenance. Low FCEmk in cows may be partially due to high somatic cell counts. To examine potential greenhouse gas (GHG) mitigation strategies for outdoor dairy cow holding areas where manure goes uncollected, experimental barnyards were constructed with either soil, sand or bark mulch surface substrates, and measurement of GHG fluxes from those barnyards was begun. Significantly higher emissions of carbon dioxide and methane, and trends for higher emissions of nitrous oxide, were recorded from bark mulch compared to soil or sand barnyards. Three dairy heifer experiments have been initiated. Eastern gamagrass has been ensiled, and the protocol was approved for an animal trial using that grass as an energy-cutter forage. A fall oat grazing trial was conducted comparing two oat cultivars with traditional confinement feeding. In an experiment comparing the effects of rotational grazing with conventional total mixed ration on subsequent first-lactation performance, weaned dairy heifers were either rotationally grazed in temperate grass pastures or fed a conventional total mixed ration while in confinement. Final preparation and characterization of various condensed tannin fractions is underway in a collaborative project. The tannin fractions will be applied to alfalfa tissue and isolated protein to assess how tannin composition and structure influences the pregastric and gastrointestinal degradability of protein. In order to properly assess the role of tannins in modulating protein digestion, an improved colorimetric method is also being developed to more accurately quantify extractable and insoluble forms of condensed tannins in forages and other plant materials. Two cuttings of alfalfa were ensiled using three different treatments: untreated, a microbial inoculant, and formic acid. The silos were opened and the silages were analyzed for fermentation characteristics. Ruminal in vitro fermentations of the silages and silage extracts are in progress to determine possible factors influencing the rumen fermentation inoculated silage.

4. Accomplishments
1. More accurate assessment of nitrogen use will aid in reducing greenhouse gas emissions from the global dairy sector. The anticipated increases in global demand for food, especially for animal products, necessitate an urgent search for practices that enhance nitrogen use efficiency and reduce environmental nitrogen loss (ammonia, nitrate, nitrous oxide) from agricultural production. The International Panel on Climate Change requires member countries to determine and report agricultural greenhouse gas emissions. In an effort to provide more accurate information for countries making these assessments, an ARS scientist from Madison, Wisconsin was assigned to the Food and Agriculture Organization of the United Nations, Animal Production and Health Division, for six months. He analyzed data on dairy cattle populations, feed, and milk production from 144 countries and determined more accurate values for nitrogen use efficiency and manure nitrogen excretion. These values may be used to estimate more accurately ammonia and nitrous oxide emissions from the global dairy sector. The improved accuracy of manure nitrogen excretion calculations derived from this study should enhance regional, production system, and global determinations of nitrogen loss from dairy farms during the collection, storage, and land application of manure, and it should more accurately reflect the amount of manure nitrogen actually recycled through crops and pastures.

2. Improved, more accurate assay developed to measure tannins in plant material. Condensed tannins have a unique role in numerous biological processes such as the release of nutrients from foods, feeds, and decaying plant litter; the palatability and flavor of food and beverages; and the incidence of certain diseases in humans and animals. But scientists trying to better understand these processes have been hampered by the difficulty of accurately quantifying condensed tannins in plant materials. Therefore, ARS researchers at Madison, Wisconsin in collaboration with university scientists, developed and tested an improved acetone-butanol-HCl assay that completely solubilizes and more accurately quantifies condensed tannins in forage plants. Ongoing studies are aimed at further developing the method for the analysis of extractable and insoluble forms of condensed tannins in a wide array of plant materials. It is anticipated that the improved assay will be widely used by scientists in a variety of disciplines to better understand the effects of condensed tannins on living systems and to improve the use of tannin-containing plants and extracts for livestock production and for promoting human health.

Review Publications
Contreras-Govea, F.E., Muck, R.E., Broderick, G.A., Weimer, P.J. 2013. Lactobacillus plantarum effects on silage fermentation and in vitro microbial yield. Animal Feed Science And Technology. 179(1):61-68.

Muck, R.E. 2013. Recent advances in silage microbiology. Agricultural and Food Science. 22(1):3-15.

Powell, J.M., Macleod, M., Vellinga, T., Opio, C., Falcucci, A., Tempio, G., Steinfeld, H., Gerber, P. 2013. Feed-milk-manure nitrogen relationships in global dairy production systems. Livestock Science. 152(2-3):261-272. Available:

Muck, R.E., Weinberg, Z.G., Contreras-Govea, F.E. 2013. Silage extracts used to study the mode of action of silage inoculants in ruminants. Agricultural and Food Science. 22(1):108-114.

Grabber, J.H., Zeller, W.E., Mueller Harvey, I. 2013. Acetone enhances the direct analysis of Procyanidin- and Prodelphinidin-based condensed tannins in lotus species by the butanol-HCl-iron assay. Journal of Agricultural and Food Chemistry. 61:2669-2678.

Last Modified: 06/24/2017
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