Management of metabolic hydrogen ([H]) in the rumen has been identified as an important consideration when reducing ruminant CH4 emissions. However, little is known about hydrogen flux and microbial rumen population responses to CH4 inhibition when animals are fed with slowly degradable diets. The effects of the anti-methanogenic compound, chloroform, on rumen fermentation, microbial ecology and H2 /CH4 production were investigated in vivo. Eight rumen fistulated Brahman steers were fed a roughage hay diet (Rhode grass hay) or roughage hay:concentrate diet (60:40) with increasing levels (low, mid and high) of chloroform in a cylcodextrin matrix. The increasing levels of chloroform resulted in an increase in H2 expelled as CH4 production decreased with no effect on dry matter intakes. The amount of expelled H2 per mole of decreased methane, was lower for the hay diet suggesting a more efficient redirection of hydrogen into other microbial products compared with hay:concentrate diet. A shift in rumen fermentation towards propionate and branched-chain fatty acids was observed for both diets. Animals fed with the hay:concentrate diet had both higher formate concentration and H2 expelled than those fed only roughage hay. Metabolomic analyses revealed an increase in the concentration of amino acids, organic and nucleic acids in the fluid phase for both diets when methanogenesis was inhibited. These changes in the rumen metabolism were accompanied by a shift in the microbiota with an increase in Bacteroidetes:Firmicutes ratio and a decrease in Archaea and Synergistetes for both diets. Within the Bacteroidetes family, some OTUs assigned to Prevotella were promoted under choloroform treatment. These bacteria may be partly responsible for the increase in amino acids and propionate in the rumen. No significant changes were observed for abundance of fibrolytic bacteria, protozoa and fungi, which suggests that fibre degradation was not impaired. The observed 30% decrease in methanogenesis did not adversely affect rumen metabolism and the rumen microbiota was able to adapt and redirect [H] into other microbial end-products for both diets. However, it is also required dietary supplements or microbial treatments to capture the additional H2 expelled by the animal to further improve rumen digestive efficiency.

The aim of this work was to investigate the effect of feeding ethyl-3-nitrooxy propionate (E3NP) and 3-nitrooxypropanol (3 NP), 2 recently developed compounds with potential antimethanogenic activity, in vitro and in vivo in nonlactating sheep on ruminal methane production, fermentation pattern, the abundance of major microbial groups, and feed degradability. Three experiments were conducted, 1 in vitro and 2 in vivo. The in vitro batch culture trial (experiment 1) tested 2 doses of E3NP and 3 NP (40 and 80 μL/L), which showed a substantial reduction of methane production (up to 95%) without affecting concentration of volatile fatty acids (VFA). The 2 in vivo trials were conducted over 16 d (experiment 2) and 30 d (experiment 3) to study their effects in sheep. In experiment 2, 6 adult nonpregnant sheep, with permanent rumen cannula and fed alfalfa hay and oats (60:40), were treated with E3NP at 2 doses (50 and 500 mg/animal per day). After 7, 14, and 15 d of treatment, methane emissions were recorded in respiration chambers and rumen fluid samples were collected for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. Methane production decreased by 29% compared with the control with the higher dose of E3NP on d 14 to 15. A decrease in the acetate:propionate ratio was observed without detrimental effects on dry matter intake. In experiment 3, 9 adult nonpregnant sheep, with permanent rumen cannula and fed with alfalfa hay and oats (60:40), were treated with E3NP or 3 NP at one dose (100mg/animal per day) over 30 d. On d 14 and d 29 to 30, methane emissions were recorded in respiration chambers. Rumen fluid samples were collected on d 29 and 30 for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. In addition, on d 22 and 23, samples of oats and alfalfa hay were incubated in the rumen of sheep to determine dry matter ruminal degradation over 24 and 48 h, respectively; no effect was observed (78.6, 78.3, and 78.8% of alfalfa and 74.2, 74.0, and 70.6% of oats in control, E3NP, and 3 NP groups, respectively). A reduction in methane production was observed for both additives at d 14 and d 29 to 30. In both treatments, the acetate:propionate ratio was significantly decreased. Likewise, total concentrations of the analyzed microbial groups in the rumen showed no difference among treatments and doses for both experiments. Both tested compounds showed promise as methane inhibitors in the rumen, with no detrimental effects on fermentation or intake, which would need to be confirmed in lactating animals.

Several technologies have been tested to reduce enteric methanogenesis, but very few have been successfully used in practical conditions for livestock. Furthermore, the consequences of reduced rumen methane production on animal performance and milk quality are poorly understood. The aim of this work was to investigate the effect of feeding bromochloromethane (BCM), a halogenated aliphatic hydrocarbon with potential antimethanogenic activity, to dairy goats on rumen methane production, fermentation pattern, the abundance of major microbial groups, and on animal performance and milk composition. Eighteen goats were allocated to 2 experimental groups of 9 animals each: treated (BCM+) or not (BCM-) with 0.30 g of BCM/100 kg of body weight per day. The BCM was administered per os in 2 equal doses per day from parturition to 2 wk postweaning (10 wk). After weaning, methane emissions were recorded over 2 consecutive days (d 57 and 58 on treatment) in polycarbonate chambers. On d 59, individual rumen fluid samples were collected for volatile fatty acid (VFA) analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. On d 69 and 70, daily milk production was recorded and samples were collected for determination of fat, protein, lactose, casein, and total solids concentration by infrared spectrophotometry, and fatty acid composition by gas chromatography. Treatment with BCM reduced methane production by 33% (21.6 vs. 14.4 L/kg of DMI) compared with nontreated animals, although it did not affect the abundance of rumen bacteria, protozoa, and total methanogenic archaea. The observed improvement in the efficiency of digestive processes was accompanied by a 36% increase in milk yield, probably due to the more propionic type of rumen fermentation and an increase in VFA production. The increase in milk yield was not accompanied by any changes in the concentrations or yields of fat, protein, or lactose. Despite the substantial decrease in methane production, only minor changes in milk fatty acid profile were observed, suggesting that ruminal biohydrogenation pathways were not affected. Compounds that influence terminal biochemical pathways for methane production deserve further development for future application in the dairy goat sector.

Japanese goats fed a diet of 50% Timothy grass and 50% concentrate with increasing levels of the anti-methanogenic compound, bromochloromethane (BCM) were investigated with respect to the microbial shifts in the rumen. Microbial ecology methods identified many species that exhibited positive and negative responses to the increasing levels of BCM. The methane-inhibited rumen appeared to adapt to the higher H2 levels by shifting fermentation to propionate which was mediated by an increase in the population of hydrogen-consuming Prevotella and Selenomonas spp. Metagenomic analysis of propionate production pathways was dominated by genomic content from these species. Reductive acetogenic marker gene libraries and metagenomics analysis indicate that reductive acetogenic species do not play a major role in the BCM treated rumen.

The growing interest in reducing methane (CH₄) emissions from ruminants by dietary means is constrained by the complexity of the microbial community in the rumen of the adult animal. The aim of this work was to study whether intervention in early life of goat kids has an impact on methane emissions and the microbial ecosystem in the rumen and whether the effects persist postweaning. Sixteen doe goats giving birth to 2 kids each were randomly split into 2 experimental groups: 8 does were treated (D+) with bromochloromethane (BCM) after giving birth and over 2 mo, and the other 8 does were not treated (D-). In both groups of does, 1 kid per doe was treated with BCM (k+) for 3 mo, and the other was untreated (k-), resulting in 4 experimental groups: D+k+, D+k-, D-k+, and D-k-. Methane emissions were recorded, and ruminal samples were collected from kids at 2 mo of age (weaning, W) and 1 (W+1) and 4 (W+4) mo later. At W+1 mo, CH₄ emissions by k+ kids were 52% and 59% less than untreated kids (in D+ and D- groups, respectively). However, at W+4 mo, only D+k+ kids remained lower (33%) emitters and exhibited greater daily BW gain (146 g/d) compared with the other 3 groups (121.8 g/d). The analysis of the archaeal community structure by Denaturing Gradient Gel Electrophoresis (DGGE)showed a strong effect of BCM treatment on does and kids that persisted only in D+k+ kids. The study showed that the application of BCM during early life of kids modified the archaeal population that colonized the rumen, which resulted in decreased CH₄ emissions around weaning. The effect is influenced by the treatment applied to the doe and persisted 3 mo later in D+k+ kids. Copyright © 2013. American Society of Animal Science .