Min Wang1, Rong Wang2, Tian Yu Xie3, Peter H Janssen4, Xue Zhao Sun4, Karen A Beauchemin5, Zhi Liang Tan6, Min Gao7. 1. 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; 2. 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; 3. 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; 4. AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand; and. 5. Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Canada. 6. 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. 7. Institute of Animal Nutrition and Feed, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Hohhot, China;
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.
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.
Authors: Henk J van Lingen; Joan E Edwards; Jueeli D Vaidya; Sanne van Gastelen; Edoardo Saccenti; Bartholomeus van den Bogert; André Bannink; Hauke Smidt; Caroline M Plugge; Jan Dijkstra Journal: Front Microbiol Date: 2017-03-17 Impact factor: 5.640