Emission from ruminants has become one of the largest sources of anthropogenic methane emission in China. The structure of the rumen flora has a significant effect on methane production. To establish a more accurate prediction model for methane production, the rumen flora should be one of the most important parameters. The objective of the present study was to investigate the relationship among changes in rumen flora, nutrient levels, and methane production in sheep fed with the diets of different forage-to-concentration ratios, as well as to screen for significantly different dominant genera. Nine rumen-cannulated hybrid sheep were separated into three groups and fed three diets with forage-to-concentration ratios of 50:50, 70:30, and 90:10. Three proportions of the diets were fed according to a 3 × 3 incomplete Latin square, design during three periods of 15d each. The ruminal fluid was collected for real-time polymerase chain reaction (real-time PCR), high-throughput sequencing and in vitro rumen fermentation in a new real-time fermentation system wit. Twenty-two genera were screened, the abundance of which varied linearly with forage-to-concentration ratios and methane production. In addition, during the 12-hour in vitro fermentation, the appearance of peak concentration was delayed by 26-27min with the different structure of rumen bacteria. The fiber-degrading bacteria were positively correlated with this phenomenon, but starch-degrading and protein-degrading bacteria were negative correlated. These results would facilitate macro-control of rumen microorganisms and better management of diets for improved nutrition in ruminants. In addition, our findings would help in screening bacterial genera that are highly correlated with methane production.

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The apparent metabolizable energy ( AME ), AME corrected to zero-nitrogen retention ( AMEn ), and net energy ( NE ) values of 2 corn samples both stored for 3 yr were determined in laying hens with reference diet substitution method. Reference diet was formulated according to standard layer requirement, and test diets contained 50% of corn samples and 50% of the reference diet. Fifty-four Hy-Line Brown hens at the age of 36 wk were used. The heat production and energy metabolism of birds were measured in open-circuit respiratory chambers with 6 replicates (3 birds per replicate) per diet in a randomized design. Birds were fed experimental diets for 7 D in the chamber as adaptation. During the following 3 D, feed intake, metabolizable energy value, nitrogen balance, energy balance, egg production, O 2 consumption, CO 2 production, and energy efficiency were determined. The AME values of corn 1 and corn 2 were 3,485 and 3,675 kcal/kg DM, respectively. The corresponding AMEn values were 3,452 and 3,596 kcal/kg DM, and the NE values were 2,575 and 2,693 kcal/kg DM, respectively. The NE:AME ratios of corn 1 and corn 2 were 74.4 and 73.3%, respectively. The NE:AMEn ratios of corn 1 and corn 2 were 75.0 and 74.9%, respectively. The AME, AMEn, and NE values of the 2 corn samples both stored for 3 yr were lower than the literature values for fresh corn.

The objective of this study was to investigate the effects of origanum oil (ORO), hydrolysable tannins (HYT) and tea saponin (TES) on methane (CH 4 ) emission, rumen fermentation, productive performance and gas exchange in sheep by using in vitro and in vivo methods. The ORO, HYT and TES additive levels were normalized per kg dry matter (DM) in both in vitro and in vivo experiments: ORO‐0, 10, 20 and 40 ml/kg; HYT‐0, 15, 30 and 60 g/kg; and TES‐0, 15, 30 and 60 g/kg, respectively. During in vitro incubation, 40 ml/kg ORO linearly decreased CH 4 emission ( p < 0.05); 20 and 40 ml/kg ORO cubically decreased carbon dioxide (CO 2 ) production ( p < 0.05), and rumen pH was cubically raised with the increasing ORO additive level ( p < 0.01). The 60 g/kg HYT cubically decreased CH 4 production ( p < 0.05). The pH of 60 g/kg HYT was higher than that of 15 and 30 g/kg ( p < 0.01); the pH of 20 g/kg TES was higher than that of 5 g/kg ( p < 0.05). In the in vivo experiments, 40 ml/kg ORO inhibited dry matter intake ( p < 0.01) cubically and reduced average daily gain (ADG) and feed conversion ratio (FCR) cubically ( p < 0.05), and 20 or 40 ml/kg ORO linearly decreased CH 4 production based on per day or metabolic weight (W 0.75 ) ( p < 0.05). Both 30 and 60 g/kg HYT linearly inhibited CH 4 emission on the bases of per day and W 0.75 ( p < 0.05). The 20 g/kg TES improved the apparent digestibility of crude protein ( p < 0.05), 10 and 20 g/kg of TES decreased CH 4 emission ( p < 0.05), and 5 g/kg of TES reduced O 2 consumption and CO 2 production ( p < 0.05). In conclusion, these three plant extracts all showed the abilities on mitigating CH 4 emission of sheep with appropriate additive ranges.