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- Title
Environmental Consequences of Overfeeding Protein to Beef Cattle.
- Authors
Place, S. E.
- Abstract
Reactive nitrogen (Nr) emissions from beef cattle production can contribute to both air and water pollution. However, Nr (biologically available N) is also essential for the growth of plants and animals. Feed N intake is the major driver of total Nr excretion by beef cattle and most feed N is in the form of dietary protein. Beef cattle excrete Nr into the environment in 2 main ways: the feces and urine. Most fecal N is excreted in an organic form and sources can include undigested feed N, microbial N, and endogenous N. Urinary N is excreted mostly as urea, but also includes compounds such as purine derivatives and creatinine. As N intake of cattle increases, both fecal N and urinary N excretion will increase; however, urinary N is excreted at an increasing rate as compared to fecal N. Once excreted from the animal, urinary N, and especially urea-N, can undergo several transformations that can lead to an increase in Nr in the environment. Specifically, urinary urea-N can be converted to ammonium/ammonia and then be emitted to the atmosphere as ammonia gas through volatilization. Ammonia can lead to particulate matter formation, acidification of terrestrial and aquatic ecosystems, and eutrophication of water bodies once deposited. Alternatively, ammonium can undergo the biological process of nitrification in soil leading to the production of nitrate (NO3 -), which may be used by plants or microorganisms or leached into groundwater. Nitrate can undergo the biological process of denitrification, thereby leading to the production of nitrogen gas (N2). During the denitrification process, nitric oxide (NO) and nitrogen dioxide (NO2) can be emitted (collectively known as NOx) as can the potent greenhouse gas nitrous oxide (N2O). Emissions of NOx can lead to particulate matter formation and can drive the production of tropospheric ozone. In addition to being a greenhouse gas 265 times more potent than carbon dioxide at trapping heat in the Earth's atmosphere on a 100-yr time scale, N2O emissions can also lead to the destruction of stratospheric ozone. Thus, feeding dietary protein at concentrations above animal requirements can lead to an increase Nr emissions from beef cattle production and negative environmental sustainability outcomes.
- Subjects
BEEF cattle feeding &; feeds; PROTEINS in animal nutrition; NITROGEN in animal nutrition
- Publication
Journal of Animal Science, 2016, Vol 95, p60
- ISSN
0021-8812
- Publication type
Abstract
- DOI
10.2527/ssasas2017.0122