In the May-June 2011 issue of the Journal of Environmental Quality, a team led by Mark Powell, a soil scientist with the USDA Agricultural Research Service’s U.S. Dairy Forage Research Center in Madison, WI, describes how natural plant compounds known as tannins can reduce both the amount of nitrogen cows excrete in urine, and the action of a microbial enzyme in manure that converts the nitrogen into ammonia on the barn floor.
The U.S. EPA already monitors ammonia emissions from large animal operations under the “Superfund” act, and in April a coalition of citizen groups petitioned the agency to begin regulating ammonia under the Clean Air Act, as well. Besides its pungent smell, ammonia that volatilizes from cattle manure is highly reactive in the atmosphere, forming particulates that travel long distances and contribute to environmental problems such as acid rain, nutrient pollution, and smog.
Feeding tannins to cattle could not only help dairy farmers reduce these impacts and meet regulatory standards, Powell says, but tannins could also boost nitrogen use efficiency in cows, thereby decreasing the need for expensive protein supplements. Only 20 to 35% of feed nitrogen ends up in milk on commercial dairy farms, with the remainder excreted about equally in manure and urine as the compound, urea.
Urea is produced when nitrogen-rich proteins break down mainly in the cow rumen, forming ammonia gas that’s eventually converted to urea before being excreted. Tannins are thought to cut urea production by somehow allowing more protein to escape digestion in the rumen and enter the cow intestine, where it’s used more efficiently to produce milk protein.
Tannins are perhaps best known for their role in leather tanning, but Powell began investigating them in ruminant feed more than two decades ago in West Africa. In the communities where he worked, tannin-rich shrubs were grown as windbreaks, and to amend the soil and feed livestock. Tannins in the diets of cattle, sheep and goats are in fact well-studied in the tropics, where the vegetation tends to be naturally higher in the astringent plant chemicals, Powell explains. “But tannin research, in terms of ruminant nutrition, is relatively new in temperate environments.”
In the new study, Powell and dairy scientists from the University of Wisconsin-Madison fed tannin extracts from red quebracho and chestnut trees to dairy cows that also received two concentrations of crude protein: a low level of 15.5% protein, and a higher one of 16.8%. What they found is that dietary tannin cut ammonia emissions from the cows’ manure by an average of 30% at the low protein level, 16% at the high level, or 23% overall. In other words, cows that consumed tannin expelled significantly less urea, thus making less available for conversion to ammonia.
But a drop in urea production wasn’t the only effect. To his surprise, Powell discovered that tannins also appear to inhibit urease, the enzyme that converts urea to ammonia. Urease activity in the feces of tannin-fed cows was significantly lower than in the feces of control animals, resulting in an 11% drop in emitted ammonia—or one-third of tannin’s total impact on emissions at the high protein level. And when the researchers applied tannin directly to manure on the barn floor (rather than feeding it to cows), the effect was even greater: Ammonia emissions declined by nearly 20%.
The tannin sources investigated in the study are already approved for animal feed, and “the levels we used amount to pennies per cow per day,” Powell says, suggesting they could offer a cost-effective means to cut ammonia losses from the barn floor, as well as from manure that’s applied to farm fields as fertilizer. Powell is now working with chemists to determine exactly which compounds in the tannin mixtures produce the effect, with an eye toward manufacturing a synthetic substitute later on.
In the meantime, he has set his sights on another important air pollutant that is prodigiously produced by cows. “We have another experiment looking at higher doses of tannin in dairy cattle,” he says. “We want to see if it can reduce methane emissions.”
The full article is available for no charge for 30 days following the date of this summary. View the abstract at https://www.agronomy.org/publications/jeq/abstracts/40/3/907.
The Journal of Environmental Quality is a peer-reviewed, international journal of environmental quality in natural and agricultural ecosystems published six times a year by the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and the Soil Science Society of America (SSSA). The Journal of Environmental Quality covers various aspects of anthropogenic impacts on the environment, including terrestrial, atmospheric, and aquatic systems.
The American Society of Agronomy (ASA) www.agronomy.org, is a scientific society helping its 8,000+ members advance the disciplines and practices of agronomy by supporting professional growth and science policy initiatives, and by providing quality, research-based publications and a variety of member services.
Sara Uttech | Newswise Science News
Alkaline soil, sensible sensor
03.08.2017 | American Society of Agronomy
New 3-D model predicts best planting practices for farmers
26.06.2017 | Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences