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RESEARCH ARTICLE
Contents Vol 50(8)

Effects of dietary nitrate on fermentation, methane production and digesta kinetics in sheep

J. V. Nolan A C , R. S. Hegarty B , J. Hegarty A , I. R. Godwin A and R. Woodgate B
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A School of Environmental and Rural Science, University of New England, Armidale, NSW 2350, Australia.

B Industry and Investment, Armidale, NSW, Australia.

C Corresponding author. Email: jnolan@une.edu.au

This paper is part of the ASAP Special Issue (Volume 50, Issue 5–6): ‘Livestock Production in a Changing Environment’

Animal Production Science 50(8) 801-806 https://doi.org/10.1071/AN09211
Submitted: 16 December 2009  Accepted: 27 May 2010   Published: 31 August 2010

Abstract

The effects of dietary nitrate on DM digestion, rumen volatile fatty acid concentrations, microbial protein outflow, rumen water kinetics, and methane production were studied. Eight rumen-cannulated sheep were acclimated to a diet consisting of chaffed oaten hay supplemented with either 4% KNO3 or 0% KNO3 but made iso-nitrogenous by the addition of urea. Nitrate supplementation did not affect blood methaemoglobin concentration, DM intake, whole tract or ruminal DM digestibility and the sheep appeared healthy at all times throughout the acclimation and experimental periods. Nitrate did cause changes in rumen fermentation consistent with its acting as a high-affinity hydrogen acceptor, i.e. there was a tendency towards a lower molar percentage of propionate in the rumen volatile fatty acids, and higher molar ratio of acetate to propionate. Methane yield (MY, L methane/kg DM intake) was reduced by 23% in KNO3-supplemented sheep (P < 0.05) and these sheep tended to have a shorter mean fluid retention time in the rumen (MRT). There was a significant association between MRT and MY, such that a shorter MRT was associated with a lower MY. The results confirmed that the presence of nitrate in the diet lowers enteric methane production even though there was considerable between-animal variation in gut kinetics and methane production.


Acknowledgements

Thanks are due to Dr Simon Bird for enumeration of protozoa and to Mr Stuart McClelland for assistance with calorimeter operation. Funding for this work was provided by the Australian Government Department of Agriculture, Fisheries and Forestry as part of the Climate Change Research Program and by Meat and Livestock Australia.


References


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