title: Shifts in Rumen Fermentation and Microbiota Are Associated with Dissolved Ruminal Hydrogen Concentrations in Lactating Dairy Cows Fed Different Types of Carbohydrates.
abstract: Different carbohydrates ingested greatly influence rumen fermentation and microbiota and gaseous methane emissions. Dissolved hydrogen concentration is related to rumen fermentation and methane production.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors: Key Laboratory for Agro-Ecological Processes in Subtropical Regions, South Central Experimental Station of Animal Nutrition and Feed Science in the Ministry of Agriculture, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China; Hunan Co-Innovation Center of Animal Production Safety (CICAPS), Changsha, China;
authors: Min
authors: M
authors: Wang
authors: Key Laboratory for Agro-Ecological Processes in Subtropical Regions, South Central Experimental Station of Animal Nutrition and Feed Science in the Ministry of Agriculture, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China;
authors: Rong
authors: R
authors: Wang
authors: Key Laboratory for Agro-Ecological Processes in Subtropical Regions, South Central Experimental Station of Animal Nutrition and Feed Science in the Ministry of Agriculture, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China; Institute of Animal Nutrition and Feed, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Hohhot, China;
authors: Tian Yu
authors: TY
authors: Xie
authors: AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand; and.
authors: Peter H
authors: PH
authors: Janssen
authors: AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand; and.
authors: Xue Zhao
authors: 0000-0003-1706-1339
authors: XZ
authors: Sun
authors: Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Canada.
authors: Karen A
authors: KA
authors: Beauchemin
authors: Key Laboratory for Agro-Ecological Processes in Subtropical Regions, South Central Experimental Station of Animal Nutrition and Feed Science in the Ministry of Agriculture, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China; zltan@isa.ac.cn.
authors: Zhi Liang
authors: ZL
authors: Tan
authors: Institute of Animal Nutrition and Feed, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Hohhot, China;
authors: Min
authors: M
authors: Gao
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D005260:Female; D005285:Fermentation; D045848:Fibrobacter / Q000302:isolation & purification / Q000378:metabolism; D000069196:Gastrointestinal Microbiome; D006859:Hydrogen / Q000378:metabolism*; D007774:Lactation; D008697:Methane / Q000378:metabolism; D008962:Models, Theoretical; D018720:Prevotella / Q000302:isolation & purification / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D020357:Selenomonas / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D006859:Hydrogen; D008697:Methane
keywords: Gibbs free energy; dairy cow; dietary carbohydrate; fiber; hydrogen; methane; rumen fermentation pathway; rumen microbe; starch