Effects Of Dietary Energy Density On Rumen Fermentation Characteristics And Microbial Populations

This study was conducted to evaluate the effects of dietary energy density on rumen fermentation characteristics and microbial populations. First, using nylon bag method to investigate the rumen degradation characteristics of individual feed ingredients, and then studied the two kinds of dietary energy density on rumen fermentation characteristics and microbial populations.In experiment1, using nylon bag method to investigate the rumen degradation of corn grain, wheat bran, soybean meal and rapeseed meal at0,2,6,12,24,48and72h of fermention time points. Each cattle had two repeat at every time point. The results showed that:(1) OM, CP, DM, ADF and NDF degradation rate gradually with the extension of time was increasing.(2) The soybean meal effective degradation rate was significant higher than rapeseed meal (P<0.01),100.08%higher than the rapeseed meal; the corn in effective degradation rate higher than the wheat bran significantly (P<0.01),16.04%higher than wheat bran.(3) The soybean meal effective degradation rate was significant higher than rapeseed meal (P<0.01),50.52%higher than the rapeseed meal; the corn in effective degradation rate higher than the wheat bran significantly (P<0.01),7.20%higher than wheat bran.(4) Effective degradation rate of dry matter:soybean meal (44.76%)> wheat bran (42.23%)> corn (41.17%)> rapeseed meal (30.82%).(5) Corn, wheat bran, soybean meal and rapeseed meal of the effective degradation rate of NDF were44.42%,49.53%,46.54%and25.64%, respectively.(5) Corn, soybean and wheat bran acid degradation rate (72h) of ADF were significant higher than rapeseed meal (P<0.01), corn and soybean meal were significantly higher than wheat bran (P<0.01).In experiment2, effects of dietary energy density on rumen fermentation characteristics and microbial populations. The nutrient levels of diets were formulated to meet the recommendations by feeding standard of beef cattle of china (2004). The treatments were organized in three levels of dietary energy density. Treatment A (n=6) was low dietary energy density (1.1×Nemf,1.3×CP). The treatments B and C were intermediate dietary energy density (1.3×Nemf,1.3×CP) and high dietary energy density (1.5×Nemf,1.3×CP), respectively. The synchrony index of N to OM was calculated according to the rumen degradation characteristics of individual feed ingredients. Recorded the amount of cumulative GP at0,2,4,6,8,12,16and24h, and all time points of the fermentation medium were used to analyze pH, ammonia nitrogen (NH3-N), volatile fatty acid (VFA), bacteria protein, protozoa protein, microbial and S6K and target of rapamycin (TOR) population. The results showed that:(1) with dietary energy density increasing synchrony index (SI) was increased.(2) With dietary energy density increasing bacteria protein, protozoa protein, microbial protein, propionic acid, acetic acid, butyric acid and total volatile fatty acid were significantly increased (P<0.05); the concentration of ammonia nitrogen decreased (P<0.05).(3) There were extreme significantly positive correlations between dietary energy density and bacteria protein, protozoa protein, microbial protein concentrations (P<0.01)(Correlation coefficient0.738,0.841and0.856, respectively).(4) With dietary energy density increasing Protozoa were significantly increased (P<0.05). With dietary energy density increasing Streptococcus bovis (Non-structure carbohydrates degradation bacterium) ruminicola population were significantly increased (P<0.05). Low dietary energy density group of Bacterorides amylophilus (Non-structure carbohydrates degradation bacterium) population was significant lowed (16h) than intermediate and high dietary energy density group (P<0.05). High dietary energy density group of Butyrivibrio fibrisolvens (Structure carbohydrates degradation bacterium) population was extreme significant lowed (8h) than intermediate and low dietary energy density group (P<0.01), but low dietary energy density group was extreme significant lowed (24h) than intermediate and high dietary energy density group (P<0.01).(5) With dietary energy density increasing target of rapamycin (TOR) was significantly increased (P<0.05), but S6K was not significant (P>0.05).In summary, soybean meal more easily provide nitrogen source to ruminal microbes, provides higher rapeseed meal of rumen bypass protein; corn more easily rumen degradation, and was good provide carbon sources to ruminal microbes. The energy mainly through affect the synchronization of energy and nitrogen metabolism, and then change of the ruminal microbial population, which significantly affect rumen fermentation characteristics. The synchrony index (SI) was increased by concentration of dietary increasing, and which benefit of protozoa and non-structure carbohydrates degradation bacterium were growth, it promoted the rumen fermentation, so as to make the microbial protein increasing.concentration...