Dietary nitrate metabolism and enteric methane mitigation in sheep consuming a protein-deficient diet

Author(s)
Villar, L
Hegarty, Roger
Van Tol, M
Godwin, I
Nolan, J
Publication Date
2020
Abstract
It was hypothesised that the inclusion of nitrate (NO<sub>3</sub><sup>–</sup>) or cysteamine hydrochloride (CSH) in a protein deficient diet (4.8% crude protein; CP) would improve the productivity of sheep while reducing enteric methane (CH<sub>4</sub>) emissions. A complete randomised designed experiment was conducted with yearling Merino sheep (<i>n</i> = 24) consuming a protein deficient wheaten chaff control diet (CON) alone or supplemented with 1.8% nitrate (NO<sub>3</sub><sup>–</sup>; DM basis), 0.098% urea (Ur, DM basis) or 80 mg cysteamine hydrochloride/kg liveweight (CSH). Feed intake, CH<sub>4</sub> emissions, volatile fatty acids (VFA), digesta kinetics and NO<sub>3</sub><sup>–</sup>, nitrite (NO<sub>2</sub><sup>–</sup>) and urea concentrations in plasma, saliva and urine samples were measured. There was no dietary effect on animal performance or digesta kinetics (<i>P</i> > 0.05), but adding NO<sub>3</sub><sup>–</sup> to the CON diet reduced methane yield (MY) by 26% (<i>P</i> = 0.01). Nitrate supplementation increased blood MetHb, plasma NO<sub>3</sub> <sup>–</sup> and NO<sub>2</sub><sup>–</sup> concentrations (<i>P</i> < 0.05), but there was no indication of NO<sub>2</sub><sup>–</sup> toxicity. Overall, salivary NO<sub>3</sub><sup>–</sup> concentration was greater than plasma NO<sub>3</sub><sup>–</sup> (<i>P</i> < 0.05), indicating that NO<sub>3</sub><sup>–</sup> was concentrated into saliva. Our results confirm the role of NO<sub>3</sub><sup>–</sup> as an effective additive to reduce CH<sub>4</sub> emissions, even in a highly protein-deficient diet and as a source of additional nitrogen (N) for microbial protein synthesis via N-recycling into saliva and the gut. The role of CSH as an additive in low quality diets for improving animal performance and reducing CH<sub>4</sub> emissions is still unclear.
Citation
Animal Production Science, v.60 (2)
ISSN
1836-5787
1836-0939
Link
Publisher
CSIRO Publishing
Title
Dietary nitrate metabolism and enteric methane mitigation in sheep consuming a protein-deficient diet
Type of document
Journal Article
Entity Type
Publication

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