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

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.

Applicability of short-term emission measurements for on-farm quantification of enteric methane

“…In groups of grazing ruminants, methane release rate follows a diurnal biphasic pattern with peak emission rates in mid-morning and again in late afternoon (Figure 1a and b). These emission peaks probably coincide with bouts of more intensive grazing known to occur in the morning and at night (Champion et al, 1994).Emission rate rises and falls after eating (Mathers and Walters, 1982;Nolan et al, 2010) in response to substrate supply. Eating changes the ruminal contraction frequency in sheep and (less so) in cattle (Waghorn and Reid, 1983).…”

“…Emission rate rises and falls after eating (Mathers and Walters, 1982;Nolan et al, 2010) in response to substrate supply. Eating changes the ruminal contraction frequency in sheep and (less so) in cattle (Waghorn and Reid, 1983).…”

Technical options for the mitigation of direct methane and nitrous oxide emissions from livestock: a review

“…Recent research on sheep (Sar et al, 2004;Nolan et al, 2010;van Zijderveld et al, 2010) and cattle (van Zijderveld et al, 2011a and2011b;Hulshof et al, 2012) has shown promising results with nitrates decreasing enteric CH 4 production by up to 50%. Nitrates may be particularly attractive in developing countries where forages contain negligible levels of nitrate and insufficient CP for maintaining animal production.…”

Impact of adding nitrate or increasing the lipid content of two contrasting diets on blood methaemoglobin and performance of two breeds of finishing beef steers

“…The reduction of nitrate to nitrite and then to ammonium provides an energetically more favourable route for disposal of metabolic hydrogen produced during fermentation of feed carbohydrates in the rumen than the production of CH 4 . Although nitrate has been shown in many studies to reduce CH 4 emissions from ruminants (Nolan et al, 2010;Van Zijderveld et al, 2010 andHulshof et al, 2012;Li et al, 2012), the potential for its use has been hindered due to the toxicity of the intermediate product (nitrite). In the rumen, microbes rapidly reduce nitrate to nitrite and then reduce nitrite to ammonia.…”