Meng Q, Kerley M S, Ludden P A, Belyea R L
Department of Animal Sciences, University of Missouri, Columbia 65211, USA.
J Anim Sci. 1999 Jan;77(1):206-14. doi: 10.2527/1999.771206x.
The effect of dilution rate (D) on carbohydrate, fibrous and nonfibrous, and protein fermentation by ruminal microorganisms was studied using a single-effluent continuous-culture system. The diets of fibrous carbohydrate, nonfibrous carbohydrate, or protein were formulated with soybean hulls (FC), ground corn (NFC), or isolated soy protein (PR) as the primary ingredient, respectively. Six dilution rates (.025, .050, .075, .10, .15, and .20/h of fermenter volume) were used. Digestibilities of DM, OM, and CP for the three diets and of NDF and ADF for the FC diet decreased (P<.001) as D increased, although the response of the digestibility to D varied with diet. Increasing D resulted in an increase in pH (P<.001) and a decrease (P<.001) in ammonia concentration. Daily volatile fatty acid production increased (quadratic; P<.01) for the FC and NFC diets, but decreased (quadratic; P<.001) for the PR diet. Increasing D quadratically increased (P<.001) the molar percentage of acetate and propionate, but quadratically decreased (P<.001) butyrate and valerate for the FC and NFC diets. For the PR diet, the molar percentage of propionate and valerate increased (quadratic; P<.01), whereas acetate and butyrate decreased (linear; P<.001) in response to increasing D. Molar percentage of isobutyrate and isovalerate decreased (P<.01) with increasing D for all three diets. As D increased, daily microbial N production showed quadratic responses with maximum values achieved at .126, .143, and .187/h D for the FC, NFC, and PR diet, respectively. There was a positive correlation between microbial growth efficiency (MOEFF) and D. A quadratic model fit the data of MOEFF as affected by D, and maximum MOEFF of 37.3, 59.6, and 71.4 g of bacterial N/kg OM truly fermented were calculated to be achieved at .177, .314, and .207/h D for the FC, NFC, and PR diet, respectively. Dilution rate significantly influenced the ruminal microbial fermentation of fibrous and nonfibrous carbohydrates and proteins, and was positively related to microbial yield and growth efficiency. In addition, microbial nitrogen composition, and therefore efficiency, was affected by substrate fermented.
采用单流出物连续培养系统，研究了稀释率（D）对瘤胃微生物碳水化合物、纤维和非纤维以及蛋白质发酵的影响。纤维碳水化合物、非纤维碳水化合物或蛋白质日粮分别以大豆皮（FC）、玉米粉（NFC）或大豆分离蛋白（PR）作为主要成分进行配制。使用了六种稀释率（发酵罐体积的0.025、0.050、0.075、0.10、0.15和0.20/h）。随着D的增加，三种日粮的干物质（DM）、有机物（OM）和粗蛋白（CP）以及FC日粮的中性洗涤纤维（NDF）和酸性洗涤纤维（ADF）的消化率均下降（P<0.001），尽管消化率对D的反应因日粮而异。D的增加导致pH值升高（P<0.001）和氨浓度降低（P<0.001）。FC和NFC日粮的每日挥发性脂肪酸产量增加（二次曲线；P<0.01），但PR日粮的产量下降（二次曲线；P<0.001）。D的增加使FC和NFC日粮中乙酸和丙酸的摩尔百分比呈二次曲线增加（P<0.001），但丁酸和戊酸呈二次曲线下降（P<0.001）。对于PR日粮，随着D的增加，丙酸和戊酸的摩尔百分比增加（二次曲线；P<0.01），而乙酸和丁酸下降（线性；P<0.001）。所有三种日粮中，异丁酸和异戊酸的摩尔百分比均随D的增加而下降（P<0.01）。随着D的增加，每日微生物氮产量呈二次曲线反应，FC、NFC和PR日粮分别在D为0.126、0.143和0.187/h时达到最大值。微生物生长效率（MOEFF）与D呈正相关。二次模型拟合了受D影响的MOEFF数据，计算得出FC、NFC和PR日粮分别在D为0.177、0.314和0.207/h时，真正发酵的每千克OM中细菌氮的最大MOEFF分别为37.3、59.6和71.4 g。稀释率显著影响纤维和非纤维碳水化合物以及蛋白质的瘤胃微生物发酵，并且与微生物产量和生长效率呈正相关。此外，微生物氮组成以及效率受发酵底物的影响。
