The potential of 3-nitrooxypropanol to lower enteric methane emissions from beef cattle1

Abstract

This study evaluated if 3-nitrooxypropanol reduces enteric methane (CH4) emissions when added to the diet of beef cattle. The effects of 3-nitrooxypropanol on related variables including diet digestibility, ruminal fermentation, and ruminal microorganisms were also investigated. Eight ruminally cannulated Angus heifers (549 ± 64.3 kg [mean BW ± SD]) were fed a high forage diet (backgrounding diet) supplemented with 4 levels of 3-nitrooxypropanol (0, 0.75, 2.25 and 4.50 mg/kg BW). The experiment was designed as a duplicated 4 × 4 Latin square with 2 groups of heifers and four 28-d periods. Methane emissions were measured during 3 consecutive days using metabolic chambers. Up to a 5.8% reduction in ad libitum DMI was observed when 2.5 mg/kg BW of 3-nitrooxypropanol was fed (P = 0.03). Increasing level of 3-nitrooxypropanol linearly (P < 0.001) reduced CH4, with 33% less CH4 (corrected for DMI) at the highest level of supplementation compared with the control. Feed energy lost as CH4 was also reduced when 3-nitrooxypropanol was supplemented (P < 0.001). Molar proportion of acetate was reduced (P < 0.001) and that for propionate increased (P < 0.001) with increasing dose of 3-nitrooxypropanol, which in turn led to a reduction in the acetate to propionate ratio (P < 0.001). Total copy numbers of 16S ribosomal RNA (rRNA) genes for bacteria, methanogens, and 18S rRNA genes for protozoa in ruminal contents were not affected by 3-nitrooxypropanol supplementation (P ≥ 0.31). There was no effect of 3-nitrooxypropanol on DM (P = 0.1) digestibility in the total tract. The use of 4.5 mg/kg BW of 3-nitrooxypropanol in beef cattle consuming a backgrounding diet was effective in reducing enteric CH4 emissions without negatively affecting diet digestibility.

An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production

“…Finally, the physico-chemical properties of the inhibitor molecule were rendered such that it will most likely not rely on an active transport mechanism to cross the archaeal cell membrane to enhance the chances of reaching its target. Several structural analogs of methyl-CoM were identified, synthesized and tested first in vitro (11) and, later on, in vivo using sheep (17) followed by beef (18,32) and dairy cattle (19,20). Thus far, all observations made in vitro and in vivo appear to be consistent with the above hypothesis, particularly the accumulation of hydrogen reported in this manuscript and the expected change in acetate and propionate proportions in ruminal fluid (33) reported elsewhere (18)(19)(20)32).…”

“…Another possible explanation could be more efficient ruminal fermentation with 3NOP. Others have reported increased propionate concentration in the rumen fluid of dairy cows treated with 3NOP (18)(19)(20)32). Such a shift in the pattern of ruminal fermentation would likely result in a more efficient utilization of feed energy and may improve nutrient digestibility, provided there is no negative effect on fiber degradability due to hydrogen accumulation.…”

“…Several structural analogs of methyl-CoM were identified, synthesized and tested first in vitro (11) and, later on, in vivo using sheep (17) followed by beef (18,32) and dairy cattle (19,20). Thus far, all observations made in vitro and in vivo appear to be consistent with the above hypothesis, particularly the accumulation of hydrogen reported in this manuscript and the expected change in acetate and propionate proportions in ruminal fluid (33) reported elsewhere (18)(19)(20)32). The studies with dairy cows by Haisan et al (19) and Reynolds et al (20) were relatively short-term (up to 35 d) and with cows producing up to 30-35 kg/d milk.…”

“…This compound was part of a developmental program designing specific small molecule inhibitors for methyl coenzyme-M (CoM) reductase, the enzyme that catalyzes the last step of methanogenesis, the reduction of methyl CoM and coenzyme-B (CoB) into methane and a CoMCoB complex (16). A continuous in vitro culture study (11) was followed by in vivo experiments in sheep (17), beef (18), and dairy cattle (19,20), which demonstrated that 3NOP is an effective methane inhibitor. However, these experiments were conducted using nonlactating animals (17), or were short-term (<35 d; refs.…”

Invited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions

“…There has been some variability in relationships between methane emissions and the abundance of rumen methanogens when antimethanogenic compounds have been fed. For instance, inhibitors of the enzyme methyl coenzyme-M reductase (which is involved in the last step of the methanogenic pathway), such as bromochoromethane (Denman et al, 2007), chloroform (Knight et al, 2011), or 3-nitrooxypropanol (Haisan et al, 2014), did not always result in a reduction of methanogen numbers (Romero-Perez et al, 2014. Other compounds known for their antimicrobial activities were also shown to induce reductions in both MeP and methanogen numbers (Kubo et al, 1993;Iwamoto et al, 2002).…”