Effects of nitrate addition to a diet on fermentation and microbial populations in the rumen of goats, with special reference to Selenomonas ruminantium having the ability to reduce nitrate and nitrite

Abstract

This study investigated the effects of dietary nitrate addition on ruminal fermentation characteristics and microbial populations in goats. The involvement of Selenomonas ruminantium in nitrate and nitrite reduction in the rumen was also examined. As the result of nitrate feeding, the total concentration of ruminal volatile fatty acids decreased, whereas the acetate : propionate ratio and the concentrations of ammonia and lactate increased. Populations of methanogens, protozoa and fungi, as estimated by real-time PCR, were greatly decreased as a result of nitrate inclusion in the diet. There was modest or little impact of nitrate on the populations of prevailing species or genus of bacteria in the rumen, whereas Streptococcus bovis and S. ruminantium significantly increased. Both the activities of nitrate reductase (NaR) and nitrite reductase (NiR) per total mass of ruminal bacteria were increased by nitrate feeding. Quantification of the genes encoding NaR and NiR by real-time PCR with primers specific for S. ruminantium showed that these genes were increased by feeding nitrate, suggesting that the growth of nitrate- and nitrite-reducing S. ruminantium is stimulated by nitrate addition. Thus, S. ruminantium is likely to play a major role in nitrate and nitrite reduction in the rumen.

Mode of action uncovered for the specific reduction of methane emissions from ruminants by the small molecule 3-nitrooxypropanol

“…At the low concentrations of 3-NOP and of nitrite required to completely inhibit methanogenesis, these compounds are not toxic to animals (19,35,36). 1,3-Propanediol (37) and nitrite (38) are commonly occurring intermediates in the rumen.…”

The Structural and Functional Capacity of Ruminal and Cecal Microbiota in Growing Cattle Was Unaffected by Dietary Supplementation of Linseed Oil and Nitrate

“…Effects of nitrate on ruminal protozoa are contrasting. Asanuma et al (2015) reported 86% reduction in protozoa abundance in goats receiving potassium nitrate, but their numbers were not affected in lambs (van Zijderveld et al, 2010) or cows (Guyader et al, 2015a). Similarly contrasting results were reported with the addition of linseed oil, some authors observing a linear reduction in protozoa numbers with increasing amounts of linseed (Martin et al, 2016), whereas others report no change even with high amounts of added fatty acids (Benchaar et al, 2012).…”

“…Polyunsaturated fatty acids are known to have a toxic effect on some ruminal bacteria, especially cellulolytic ones (Maia et al, 2007), however, we did not observe a reduction in the numbers of the three main cellulolytic bacteria ( Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens ). In vitro , nitrate inhibited growth of the same three species; in vivo their numbers were reduced in the rumen of goats (Asanuma et al, 2015), but increased in steers (Zhao et al, 2015) fed nitrates. Ruminococcus species adapt to nitrates, whereas methanogens and F. succinogenes do not (Zhou et al, 2012).…”

Redirection of Metabolic Hydrogen by Inhibiting Methanogenesis in the Rumen Simulation Technique (RUSITEC)

“…In the rumen, NIT decreases methanogenesis by competing for [2H] during dissimilatory nitrate reduction to ammonium (${\text{NH}}_4^{+}$; DNRA) or during denitrification leading to nitrous oxide (N 2 O) production (Yang et al, 2016). At the same time, nitrite produced as an intermediary product of DNRA would have a direct toxic effect toward methanogenic Archaea (Klüber and Conrad, 1998; Asanuma et al, 2015). Nitrate decreased CH 4 production in lactating dairy cows (21 g nitrate/kg dry matter [DM], −23.4% CH 4 ; Olijhoek et al, 2016), steers (30 g nitrate/kg DM, −29.4% CH 4 ; Newbold et al, 2014) and sheep (20 g nitrate/kg DM, −16.5% CH 4 ; de Raphélis-Soissan et al, 2014).…”