Effects of propyl propane thiosulfinate on nutrient utilization, ruminal fermentation, microbial population and methane emissions in goats

Changes in Carbohydrate Composition in Fermented Total Mixed Ration and Its Effects on in vitro Methane Production and Microbiome

The purpose of this experiment was to investigate the changes of carbohydrate composition in fermented total mixed diet and its effects on rumen fermentation, methane production, and rumen microbiome in vitro. The concentrate-to-forage ratio of the total mixed ration (TMR) was 4:6, and TMR was ensiled with lactic acid bacteria and fibrolytic enzymes. The results showed that different TMRs had different carbohydrate compositions and subfractions, fermentation characteristics, and bacterial community diversity. After fermentation, the fermented total mixed ration (FTMR) group had lower contents of neutral detergent fiber, acid detergent fiber, starch, non-fibrous carbohydrates, and carbohydrates. In addition, lactic acid content and relative abundance of Lactobacillus in the FTMR group were higher. Compared with the TMR group, the in vitro ammonia nitrogen and total volatile fatty acid concentrations and the molar proportion of propionate and butyrate were increased in the FTMR group. However, the ruminal pH, molar proportion of acetate, and methane production were significantly decreased in the FTMR group. Notably, we found that the relative abundance of ruminal bacteria was higher in FTMR than in TMR samples, including Prevotella, Coprococcus, and Oscillospira. At the same time, we found that the diversity of methanogens in the FTMR group was lower than that in the TMR group. The relative abundance of Methanobrevibacter significantly decreased, while the relative abundances of Methanoplanus and vadinCA11 increased. The relative abundances of Entodinium and Pichia significantly decreased in the FTMR group compared with the TMR group. These results suggest that FTMR can be used as an environmentally cleaner technology in animal farming due to its ability to improve ruminal fermentation, modulate the rumen microbiome, and reduce methane emissions.

Effects of oregano essential oil on in vitro ruminal fermentation, methane production, and ruminal microbial community

Different inclusion rates of oregano essential oil (OEO) were investigated for their effects on ruminal in vitro fermentation parameters, total gas, methane production, and bacterial communities. Treatments were (1) control, 0 mg/L of OEO (CON); 13 mg/L (OEO1); 52 mg/L (OEO2); 91 mg/L (OEO3); and 130 mg/L (OEO4), each incubated with 150 mL of buffered rumen fluid and 1,200 mg of substrate for 24 h using the Ankom in vitro gas production system (Ankom Technology Corp., Fairport, NY). Treatment responses were statistically analyzed using polynomial contrasts. Digestibility of DM, NDF, and ADF increased quadratically with increasing OEO inclusion rates. Digestibility of DM and NDF were highest for OEO2, whereas ADF digestibility was highest for OEO3, compared with CON, with the remaining treatments being intermediate and similar. Ammonia nitrogen concentrations decreased from CON at a quadratic rate with increasing OEO inclusion rates, and OEO2 had the lowest concentration compared with the other groups. Total VFA, acetate, propionate, butyrate, valerate, and isovalerate concentrations linearly decreased with increasing OEO inclusion rates. Total gas production levels by CON and OEO4 were greater than those of OEO1, OEO2, and OEO3 in a quadratic response, and methane production linearly decreased from CON, compared with OEO4, at a decreasing rate with OEO inclusion rates. As determined by 16S rRNA sequencing, the α biodiversity of ruminal bacteria was similar among OEO inclusion rates. Increasing OEO inclusion rates linearly increased the relative abundance of Prevotella and Dialister bacteria. Several bacteria demonstrated different polynomial responses, whereas several bacteria were similar among increasing OEO inclusion rates. These results suggested that OEO supplementation can modify ruminal fermentation to alter VFA concentrations and reduce methane emissions by extensively altering the ruminal bacterial community, suggesting an optimal feeding rate for future animal studies of approximately 52 mg/L for mature ruminants.

Use of Onion Extract as a Dairy Cattle Feed Supplement: Monitoring Propyl Propane Thiosulfonate as a Marker of Its Effect on Milk Attributes

Onion extract is used as a feed supplement for the diet of dairy cows, acting as inhibitor of methane production; however, its properties could alter sensory attributes of milk. In this work, we propose a method to evaluate the influence of this extract on milk properties, using propyl propane thiosulfonate (PTSO) as a marker. PTSO is extracted using a quick, easy, cheap, effective, rugged, and safe procedure and monitored by high-performance liquid chromatography with ultraviolet detection. The method was applied to milk samples obtained from 100 dairy cows fed during 2 months with enriched feed. In addition, a milk tasting panel was established to evaluate the PTSO residue that should not be exceeded to guarantee milk sensory attributes. It was established that a value of PTSO lower than 2 mg kg^-1 does not alter milk organoleptic properties. This fact makes onion extract an interesting alternative as a feed supplement to control the methane emissions without any influence on milk attributes.

Effects of Adaptation of In vitro Rumen Culture to Garlic Oil, Nitrate, and Saponin and Their Combinations on Methanogenesis, Fermentation, and Abundances and Diversity of Microbial Populations

This study investigated the effects of garlic oil (0.25 g/L), nitrate (5 mM), and quillaja saponin (0.6 g/L), alone and in binary or ternary combinations, on methanogenesis, rumen fermentation, and abundances of select microbial populations using in vitro rumen cultures. Potential adaptation to these compounds was also examined by repeated transfers of the cultures on alternate days until day 18. All treatments except saponin alone significantly decreased methanogenesis. Ternary combinations of garlic oil, nitrate, and saponin additively/synergistically suppressed methane production by 65% at day 2 and by 40% at day 18. Feed digestion was not adversely affected by any of the treatments at day 2, but was decreased by the combinations (binary and ternary) of garlic oil with the other inhibitors at days 10 and 18. Saponin, alone or in combinations, and garlic oil alone lowered ammonia concentration at day 2, while nitrate increased ammonia concentration at days 10 and 18. Total volatile fatty acid concentration was decreased by garlic oil alone or garlic oil-saponin combination. Molar proportions of acetate and propionate were affected to different extents by the different treatments. The abundances of methanogens were similar among treatments at day 2; however, garlic oil and its combination with saponin and/or nitrate at day 10 and all treatments except saponin at day 18 significantly decreased the abundances of methanogens. All the inhibitors, either alone or in combinations, did not adversely affect the abundances of total bacteria or Ruminococcus flavefaciens. However, at day 18 the abundances of Fibrobacter succinogenes and Ruminococcus albus were lowered in the presence of garlic oil and saponin, respectively. The results suggest that garlic oil-nitrate-saponin combination (at the doses used in this study) can effectively decreases methanogenesis in the rumen, but its efficacy may decrease while inhibition to feed digestion can increase over time.

Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome

Ruminant livestock represent the single largest anthropogenic source of the potent greenhouse gas methane, which is generated by methanogenic archaea residing in ruminant digestive tracts. While differences between individual animals of the same breed in the amount of methane produced have been observed, the basis for this variation remains to be elucidated. To explore the mechanistic basis of this methane production, we measured methane yields from 22 sheep, which revealed that methane yields are a reproducible, quantitative trait. Deep metagenomic and metatranscriptomic sequencing demonstrated a similar abundance of methanogens and methanogenesis pathway genes in high and low methane emitters. However, transcription of methanogenesis pathway genes was substantially increased in sheep with high methane yields. These results identify a discrete set of rumen methanogens whose methanogenesis pathway transcription profiles correlate with methane yields and provide new targets for CH₄ mitigation at the levels of microbiota composition and transcriptional regulation.