Production of N2 and N2O from nitrate ingested by sheep

de Raphelis-Soissan, V; Nolan, John V; Godwin, Ian R; Newbold, J R; Eyre, B D; Erler, D V; Hegarty, Roger

doi:10.1111/jpn.12725

Author(s)

de Raphelis-Soissan, V

Nolan, John V

Godwin, Ian R

Newbold, J R

Eyre, B D

Erler, D V

Hegarty, Roger

Publication Date

2017

Abstract

Supplementing ruminants with nitrate (NO− 3 ) reduces their enteric methane (CH4) emissions; however, the greenhouse gas (GHG) mitigation achieved can be partially offset by small emissions of nitrous oxide (N2O), a more potent GHG. Sheep were dosed intraruminally with 15NO- 3 to investigate whether dietary NO− 3 is a precursor of N2O and/or di-nitrogen gas (N2), and to quantify the amounts of NO− 3 recovered as N2O and N2 in gas emissions from sheep adapted or not adapted to dietary NO− 3. Ruminally cannulated sheep were adapted to a hay diet supplemented with NO− 3 (n = 3; 10 g NO− 3/kg DM) or urea (n = 3; 5.3 g urea/kg DM). On the day of the experiment all sheep were dosed intraruminally with 15NO− 3 and quickly moved into gas-tight chambers to enable recovery of 15N in N2O and N2 to be measured. Measurements of gases accumulating in the chambers were made over 10 successive 50 min periods; this enabled the amount of N2O produced, and the recovery of 15NO− 3-N in N2O and N2 to be determined over a total of 10 hr. Only 0.04% of labelled NO− 3-N was recovered as N2O, and this was not dependent (p > .05) on whether or not the animals had been adapted to dietary NO− 3. Approximatively 3% of 15NO− 3-N was recovered as 15N2, which was also not dependent (p > .05) on whether sheep had been adapted to NO− 3. Because the kinetics of rumen ammonia (NH3) were uncertain, the recovery of 15N from NO− 3 in rumen NH3 could not accurately be quantified, but our results suggest that approximately 76% of dietary NO− 3 was converted to NH3 in the rumen. We conclude that the small amount of NO− 3 recovered in N2 was evidence of denitrification, previously thought not to occur in the rumen.

Citation

Journal of Animal Physiology and Animal Nutrition, 102(1), p. e176-e182

ISSN

1439-0396

0931-2439

Link

https://hdl.handle.net/1959.11/23272

Language

en

Publisher

Wiley-Blackwell Verlag GmbH

Title

Production of N2 and N2O from nitrate ingested by sheep

Type of document

Journal Article

Entity Type

Publication

Author(s)	de Raphelis-Soissan, V Nolan, John V Godwin, Ian R Newbold, J R Eyre, B D Erler, D V Hegarty, Roger
Publication Date	2017
Abstract	Supplementing ruminants with nitrate (NO− 3 ) reduces their enteric methane (CH4) emissions; however, the greenhouse gas (GHG) mitigation achieved can be partially offset by small emissions of nitrous oxide (N2O), a more potent GHG. Sheep were dosed intraruminally with 15NO- 3 to investigate whether dietary NO− 3 is a precursor of N2O and/or di-nitrogen gas (N2), and to quantify the amounts of NO− 3 recovered as N2O and N2 in gas emissions from sheep adapted or not adapted to dietary NO− 3. Ruminally cannulated sheep were adapted to a hay diet supplemented with NO− 3 (n = 3; 10 g NO− 3/kg DM) or urea (n = 3; 5.3 g urea/kg DM). On the day of the experiment all sheep were dosed intraruminally with 15NO− 3 and quickly moved into gas-tight chambers to enable recovery of 15N in N2O and N2 to be measured. Measurements of gases accumulating in the chambers were made over 10 successive 50 min periods; this enabled the amount of N2O produced, and the recovery of 15NO− 3-N in N2O and N2 to be determined over a total of 10 hr. Only 0.04% of labelled NO− 3-N was recovered as N2O, and this was not dependent (p > .05) on whether or not the animals had been adapted to dietary NO− 3. Approximatively 3% of 15NO− 3-N was recovered as 15N2, which was also not dependent (p > .05) on whether sheep had been adapted to NO− 3. Because the kinetics of rumen ammonia (NH3) were uncertain, the recovery of 15N from NO− 3 in rumen NH3 could not accurately be quantified, but our results suggest that approximately 76% of dietary NO− 3 was converted to NH3 in the rumen. We conclude that the small amount of NO− 3 recovered in N2 was evidence of denitrification, previously thought not to occur in the rumen.
Citation	Journal of Animal Physiology and Animal Nutrition, 102(1), p. e176-e182
ISSN	1439-0396 0931-2439
Link	https://hdl.handle.net/1959.11/23272
Language	en
Publisher	Wiley-Blackwell Verlag GmbH
Title	Production of N2 and N2O from nitrate ingested by sheep
Type of document	Journal Article
Entity Type	Publication

Production of N2 and N2O from nitrate ingested by sheep

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