Effects Of Diets Supplemented With Bacillus Subtilis And Fructo-Oligosaccharide On Ruminal Fermentation And Functional Microbiota Of Sheep

The objective of present study was to investigate the effect of diets supplemented with bacillus subtilis(BS)and fructo-oligosaccharide(FOS)and their combinations on ruminal fermentation and functional microbiota of sheep.In experiment 1,five BS levels(0,5 × 108 CFU/kg,5 × 109 CFU/kg,5 × 1010 CFU/kg and 5 × 1011 CFU/kg)were supplement in diets with five concentrate to forage ratios(30:70,40:60,50:50,60:40 and 70:30)to formulate 25 kinds of fermentation substrates using a 5×5 two factorial experiment design.In experiment 2,four BS levels(0,1 × 109 CFU/kg,5 × 109 CFU/kg and 1 × 1010 CFU/kg)and five FOS levels(0,0.5%,1.0%,1.5% and 2.0% were supplement in total mixed ration to formulate 20 kinds of fermentation substrates using a 5×4 two factorial experiment design.The above two experiments were carried out in vitro fermentation to determine the optimal combination of BS and FOS.In experiment 3,sixteen Dorper × Small Tail Han sheep F1 crossed castrated rams with permanent ruminal cannulas were randomly selected and divided into four groups.Four groups of ecxpermental sheep were fed diets supplemented with 0(CK group),5 × 109 CFU/kg BS(BS group),1.5% FOS(FOS group),5 × 109 CFU/kg BS + 1.5% FOS(BF group).Results were showed as follows: 1)For levels of concentrate to forage ratios,concentrate to forage ratios 50:50 significantly promoted NH3-N,propionic acid concentration and DMD,and significantly declined acetic acid/propionic acid ratio,CH4 concentration and NDFD(P<0.05).For BS levels,5 × 109 CFU/kg BS supplementation in substrate significantly increased propionic acid concentration,DMD and NDFD(P<0.05).The concentrate to forage ratios,BS levels and interaction had significant effects on acetic acid and MCP concentration(P<0.05).2)For 1.5% FOS supplementation,CH4 and NH3-N concentration,acetic acid/propionic acid ratio in cultivated fluid were significantly decreased,MCP and propionic acid concentration,DMD,NDFD was significantly increased(P<0.05).The combination of supplemental BS and FOS had significantly interactive effects on CH4 concentration and NDFD(P<0.05),and the CH4 concentration reached the minimum and the NDFD reached the maximum in 5 × 109 CFU/kg BS and 1.5% FOS supplementation.3)The acetic acid/propionic acid ratio and methanogens of BF group were significantly declined(P<0.05),the propionic acid and protein N concentration,total activeties of CMCC and xylanase,relative quantity of R.flavefaciens,P.ruminicola,B.fibrisolvens and P.ruminicola of BF group were significantly increased(P<0.05).BS and FOS and their combinations are beneficial to ruminal ecosystem under the condition of this experiment,and BS and FOS have a significant synergy.In conclusion,under the condition of this experiment,the optimal proportion of BS supplementation is 5 × 109 CFU/kg,the optimal proportion of FOS supplementation is 1.5%,the optimal proportion of BS and FOS supplementation has a certain synergistic effect in regulation of the ruminal environment.