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The potential of
feeding nitrate to reduce enteric methane production in ruminants. A
Report to The Department of Climate Change, Commonwealth Government of
Australia, Canberra, ACT, Australia.
R A LENG AO,BSc, PHD, DRu
University of New England
The Australian Government Greenhouse Gas Office
commissioned Professor Leng to review the potential to use nitrates in ruminant
feeds to limit enteric methane production. A report was submitted to the
Governments now Department of Climate Change in October 2008. The major
reduction to ammonia can replace the reduction of carbon dioxide to methane
as a major sink for disposal of hydrogen in the rumen when included in
suitable amounts in ruminant diets.
Nitrate as a sole fermentable N source in a diet could totally inhibit
enteric methane production by ruminants.
barrier to the use of nitrate in the diet of ruminants to reduce enteric
methane production is the potential for the accumulation of nitrite in the
rumen that is anti-nutritional and can cause reduced productivity and even
death when absorbed.
Nitrite accumulation and nitrate poisoning are not encountered when animals
are adjusted to nitrate in the diet over a period of about a week.
Nitrate can be potentially most efficiently used to lower methane production
in diets that require some form of nitrogen supplementation to optimise feed
Nitrate could be applied to the large numbers of animals that are fed poor
quality diets which produce most of the enteric methane in the world.
use of nitrate in high protein feeds is unlikely to be practical. It appears
that excess protein predisposes the generation of nitrite from nitrate in
the rumen. It would also be illogical to add extra nitrogen into such diets
that would inevitably increase the excretion of N by the animal, potentially
leading to release of nitrogen oxides/methane from the excreta. Nitrogen
oxides (NOx) being considerably more potent green house gas than
reason for nitrite accumulation in the rumen needs to be explained. Drawing
on studies from natural anaerobic ecosystems amended with nitrate it is
hypothesized that nitrite production in the rumen when nitrate is fed,
results from a single group of organisms. These reduce nitrate to ammonia
using sulphide to reduce the intermediate nitrite (they are nitrate reducing
sulphide oxidising bacteria termed NR-SOB). At high nitrate concentrations
in a diet, nitrate reducing bacteria (NRB) that abound in the rumen
effectively inhibit sulphur reducing bacteria (SRB) and lower hydrogen
sulphide concentrations in the rumen. Low availability of hydrogen sulphide
inhibits or slows NR-SOB reduction of nitrite to ammonia resulting in
nitrite accumulation in the rumen. It is proposed that the population
density of NR-SOB is governed by previous diet depending on nitrate and
protein levels in the feed.
Nitrate can be safely used to lower methane production in ruminants provide
the following conditions are met
Nitrate in the feed is kept within stoichiometric requirements for efficient
Animals are adjusted to nitrate slowly.
Previous diet and the production diet are low in readily fermentable (or rumen
conditions and precautions for feeding nitrate are precisely the same for
the safe use of urea in ruminant feeds.
report is being up-dated and corrected on a continuous basis and has been
modified slightly compared to the report posted on the Department of Climate
Change website that can be accessed at
full report click here
Power-point presentation click
Older publications and presentations.
Follow the links to the left or
to read about Prof R.A Leng's latest publication "Drought and Dry Season
Feeding Strategies for Cattle, Sheep and Goats".
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