Elsevier

The Journal of Nutrition

Volume 146, Issue 9, September 2016, Pages 1714-1721
The Journal of Nutrition

Shifts in Rumen Fermentation and Microbiota Are Associated with Dissolved Ruminal Hydrogen Concentrations in Lactating Dairy Cows Fed Different Types of Carbohydrates123

https://doi.org/10.3945/jn.116.232462Get rights and content
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Abstract

Background: Different carbohydrates ingested greatly influence rumen fermentation and microbiota and gaseous methane emissions. Dissolved hydrogen concentration is related to rumen fermentation and methane production.

Objectives: We tested the hypothesis that carbohydrates ingested greatly alter the rumen environment in dairy cows, and that dissolved hydrogen concentration is associated with these changes in rumen fermentation and microbiota.

Methods: Twenty-eight lactating Chinese Holstein dairy cows [aged 4–5 y, body weight 480 ± 37 kg (mean ± SD)] were used in a randomized complete block design to investigate effects of 4 diets differing in forage content (45% compared with 35%) and source (rice straw compared with a mixture of rice straw and corn silage) on feed intake, rumen fermentation, and microbial populations.

Results: Feed intake (10.7–12.6 kg/d) and fiber degradation (0.584–0.692) greatly differed (P ≤ 0.05) between cows fed the 4 diets, leading to large differences (P ≤ 0.05) in gaseous methane yield (27.2–37.3 g/kg organic matter digested), dissolved hydrogen (0.258–1.64 μmol/L), rumen fermentation products, and microbiota. Ruminal dissolved hydrogen was negatively correlated (r < −0.40; P < 0.05) with molar proportion of acetate, numbers of fungi, abundance of Fibrobacter succinogenes, and methane yield, but positively correlated (r > 0.40; P < 0.05) with molar proportions of propionate and n-butyrate, numbers of methanogens, and abundance of Selenomonas ruminantium and Prevotella spp. Ruminal dissolved hydrogen was positively correlated (r = 0.93; P < 0.001) with Gibbs free energy changes of reactions producing greater acetate and hydrogen, but not correlated with those reactions producing more propionate without hydrogen.

Conclusions: Changes in fermentation pathways from acetate toward propionate production and in microbiota from fibrolytic toward amylolytic species were closely associated with ruminal dissolved hydrogen in lactating dairy cows. An unresolved paradox was that greater dissolved hydrogen was associated with greater numbers of methanogens but with lower gaseous methane emissions.

Key Words

rumen fermentation pathway
hydrogen
methane
dietary carbohydrate
starch
fiber
dairy cow
rumen microbe
Gibbs free energy

Abbreviations

DM
dry matter
ECM
energy-corrected milk
FC
forage content
FS
forage source
HF
high forage content
HF-RC
high forage content with 15% rice straw and 30% corn silage
HF-RS
high forage content with 45% rice straw
LF
low forage content
LF-RC
low forage content with 10% rice straw and 25% corn silage
LF-RS
low forage content with 35% rice straw
NDF
neutral detergent fiber
OM
organic matter
RC
rice straw and corn silage
RNH2
net hydrogen production relative to the amount of total volatile FA produced
RS
rice straw
VFA
volatile FA

Cited by (0)

1

Supported by the National Natural Science Foundation of China (grant nos. 31561143009, 31320103917, and 31472133), the National Key Research and Development Program of China (grant no. 2016YFD0500504), the China Agriculture Research System (grant no. CARS-37) and the Hunan province science and technology plan (grant no. 2015WK3043).

2

Author disclosures: M Wang, R Wang, TY Xie, PH Janssen, XZ Sun, KA Beauchemin, ZL Tan, and M Gao, no conflicts of interest

3

Supplemental Tables 1–3 and Supplemental Figures 1–4 are available from the Online Supporting Material link in the online posting of the article and from the same link in the online table of contents at http://jn.nutrition.org.