Effects of High Forage/Concentrate Diet on Volatile Fatty Acid Production and the Microorganisms Involved in VFA Production in Cow Rumen

Abstract

The objectives of this study were to investigate the difference in the mechanism of VFAs production combined with macrogenome technology under different forage-to-concentrate ratios and sampling times. Six ruminally cannulated Holstein cows were used in a randomized complete block design. The high forage (HF) and high concentrate (HC) diets contained 70 and 35% dietary forage, respectively. The results showed that pH was affected by sampling time, at 4 h after feeding had lower value. Excepted for acetate, the VFAs was increased with forage decreased. Propionate formation via the succinic pathway, in which succinate CoA synthetase (EC 6.2.1.5) and propionyl CoA carboxylase (EC 2.8.3.1) were key enzymes, and significantly higher in HC treatment than in HF treatment, Selenomonas, Ruminobacter, Prevotella, and Clostridium were the main microorganism that encodes these key enzymes. Butyrate formation via the succinic pathway, in which phosphate butyryltransferase (EC 2.3.1.19), butyrate kinase (EC 2.7.2.7) and pyruvate ferredoxin oxidoreductase (EC 1.2.7.1) are the important enzymes, Prevotella and Bacteroides played important role in encodes these key enzymes. This research gave a further explanation on the metabolic pathways of VFAs, and microorganisms involved in VFAs production under different F:C ration, which could further reveal integrative information of rumen function.

Profiles of Odd- and Branched-Chain Fatty Acids and Their Correlations With Rumen Fermentation Parameters, Microbial Protein Synthesis and Bacterial Populations Based on Pure Carbohydrate Incubation in Vitro

“…The observed VFA pro les in the present study are in accordance with recent studies of Wang et al [22] and Li et al [29] who all con rmed that increased dietary forage proportion could decrease TVFA in the rumen of dairy cows. Increasing proportion of fermented carbohydrate, such as starch, would enhance the microorganisms to capture released NH 3 -N to synthesize ruminal microbial protein, as illustrated by Li et al [29], which might partly explain our results.…”

“…Increasing dietary forage proportion promotes the growth of cellulose-degrading bacteria and meanwhile reduced the relative importance of amylolytic bacteria in the rumen [22,31], being consistent with our observations. However, the observed reductions of the relative abundances of all the bacteria (except S. ruminantium) across 24 h of incubation indicated microbial lysis and decomposition occurred over incubation [32] in a batch in vitro system.…”

“…Combining these results along with the positive correlation between iso-C15:0 and R. avefaciens in our experiment indicated that more abundance of this bacteria might produce high level of isoacids in the rumen. Increasing dietary forage provision would lead to improved growth of cellulolytic bacteria such as R. avefaciens [22,40], and expectedly, result in higher production iso-C15:0 in the rumen [3]. However, the strongest association we found in this study was on the population of R. avefaciens with C15:0 concentration, which seemed to be discrepant with measured cellular fatty acid compositions in pure culture studies [34,39].…”

“…RR420A, Takara, Dalian, China). The relative abundances of these bacteria were expressed as a proportion in total estimated bacterial 16S rDNA by the calculation of relative quanti cation = 2 -(Ct target-Ct total bacteria) , where Ct represents threshold cycle [22].…”

Calcium salts of long-chain fatty acids from linseed oil decrease methane production by altering the rumen microbiome in vitro

“…and succinate is converted to propionate by some bacteria. The genera Ruminobacter [71] and Succinivibrio [72] are involved in succinate production, while Succiniclasticum [73], Selenomonas [74], and Schwartzia [74] ferment succinate and produce propionate via the succinate pathway in rumen. In the present study, the genera Ruminobacter Succinivibrio, and Selenomonas.1, Succiniclasticum were increased by supplementation of CSFA at a high level or monensin compared to control, indicating that Ruminobacter and Succinivibrio might produce succinate used by Selenomonas and Succiniclasticum for propionate production in CSFA or monensin supplementation.…”