【作者】 许曾曾；

【导师】 孟庆翔；

【作者基本信息】 中国农业大学 ， 动物营养与饲料科学， 2004， 硕士

【摘要】 利用双外流连续培养系统模拟瘤胃发酵，设计2个试验，分别研究蛋白质饲料种类和添加水平对活体外瘤胃发酵和微生物氨基酸组成的影响。 试验一以大豆粕，棉籽粕，菜籽粕，花生粕，胡麻粕，鱼粉六种蛋白质饲料原料为基础配制等蛋白、等纤维(NDF)日粮，研究蛋白质饲料种类对活体外瘤胃发酵和微生物氨基酸组成的影响。结果表明，不同蛋白来源对发酵的pH值没有显著影响(P＞0.1)，但影响总挥发性脂肪酸(TVFA)产量(P＜0.02)．和乙、丙、丁酸摩尔比例(P＜00.01)，表明不同蛋白来源的处理间瘤胃微生物发酵模式发生了显著变化，实际上反映了微生物区系的改变。蛋白来源对微生物蛋白质合成效率有少量影响(P＜0.15)，其中豆粕日粮蛋白质合成效率最高，花生粕日粮最低，可能与其所含有的某些用于微生物合成的氨基酸组成有关。饲料蛋白来源显著影响瘤胃微生物有机物含量(P＜0.03)和总N中氨基酸氮比例(P＜0.001)，但不影响蛋白质含量(P＞0.2)。各种蛋白质饲料的必需氨基酸含量均明显低于瘤胃微生物的必需氨基酸含量。但是，不同蛋白饲料来源只影响瘤胃微生物中个别氨基酸(赖氨酸、胱氨酸和酪氨酸)的含量，且与日粮氨基酸组成呈负相关。总体上可以认为，微生物AA组成恒定，基本上不受日粮氨基酸比例的影响。 试验二以大豆分离蛋白(ISP)为N源配制四个粗蛋白水平日粮(ISP占精料水平的0％、33％、67％和100％)，研究饲料蛋白质添加水平对活体外瘤胃发酵和微生物氨基酸组成的影响。结果表明，随日粮蛋白水平的提高，活体外发酵pH值、NH3-N浓度和TVFA产量均呈明显的二次曲线规律变化(Q；P＜0.03)。在TVFA中各个VFA摩尔比例除异丁酸外，也均呈显著的二次曲线规律上升(Q；P＜0.02)，其最佳处理组是ISP添加水平为33％和67％的处理。无ISP的0％处理组由于缺乏可利用N源，微生物发酵程度很弱，而且发酵模式发生了改变。随日粮蛋白水平的提高，整个发酵表现为典型的蛋白质发酵，即戊酸、异丁酸和异戊酸的摩尔比例显著增高，其中以100％ISP的处理最为明显。提高日粮蛋白水平使日粮DM、OM和CP真消化率和微生物蛋白质合成效率呈显著的二次曲线规律增加(P＜0.001)。提高日粮蛋白水平不改变微生物总EAA比例(P＞0.05)，但改变瘤胃微生物氨基酸组成(P＜0.01)，EAA中是精氨酸、组氨酸、亮氨酸、蛋氨酸、苯丙氨酸和苏氨酸的比例。随大豆分离蛋白水平的提高，微生物赖氨酸含量没有显著变化，组氨酸含量呈二次曲线规律下降(Q；P＜0.05)，蛋氨酸和支链氨基酸含量呈二次曲线规律提高(Q；P＜0.05)。饲料中含量较瘤胃微生物含量低的氨基酸可能在瘤胃微生物蛋白质合成中起着至关重要的调控作用。更多还原

【Abstract】 In this study, two experiments were designed to examine the effects of protein sources and levels on rumen fermentation and microbial amino acid (AA) profile in vitro in dual-flow continuous culturesystem.Experiment 1 was conducted to determine the effects of protein sources on rumen fermentation and AA profiles of rumen bacteria in vitro. Diets were formulated with isonitrogenous amounts of soybean meal, cottonseed meal, rapeseed meal, peanut meal, linseed meal or fishmeal; NDF were similar among the diets. The protein source did not significantly (PXU) alter pH values of the fermentation, but affect total VFA concentration and molar proportions, of acetate, propionate and butyrate(P<0.001), indicating the significant changes of fermentation type among treatments and virtually the alter of the proportion of microbial species present. There was a little difference (P<0.15) in efficiency of microbial protein synthesis among treatments, with the maximum for the soybean meal diet and the minimum for the peanut meal diet. Those differences may be attributed to the profile of AAs of protein sources essential to microbial synthesis. There were significant different in bacterial OM (P<0.03 ) and the proportion of AA-N (P<0.001) , but similar in bacterial N (p>0.2). All the essential AA (EAA) contents in the protein sources were lower than those of bacterial origins. EAA contents of bacterial protein, except lysine, cystine and tyrosine which had negative correlation with that of diets, however, appeared to be similar among the diets. Generally, AA profiles of rumen bacteria appear independent of the AA profiles of diets.Experiment 2 was performed to evaluate the effect of dietary protein levels on the rumen fermentation and AA profiles of rumen bacteria in virto. Diets were formulated with four levels of isolated soy protein (ISP) at the concentration of 0%, 33%, 67% and 100%; NDF contents were similar amount the diets. The result showed that pH values, concentrations of NH3-N and total VFA increased (Q; P<0.03) quadraticly with increased CP level of diets; so did individual VFA molar proportion (Q; P<0.03), with exception of isobutyrate. Based on the above rumen fermentation parameters, ISP levels at 33% and 67% were considered to be appropriate dietary treatments. Because of the deficency of available N source, the fermentation of 0% ISP treatment was much poor, and the fermentation pattern was different from others. As protein level in the diets increased, typical protein fermentation was observed: molar proportion of valerate, isobutyrate and isovalerate increased significantly, and 100% ISP treatment had the maximum. True digestibility of dietary DM, OM, CP and the efficiency of microbial synthesis showed significantly quadratic increase (Q; P<0.001). Increasing dietary protein levels resulted in similar (P>0.05) ratio of total EAA or non-essential AA to total AA of microbial proteins, but in changed microbial individual AA proportions (P<0.01), including those EAA of arginine, histidine, leucine, methionine, phenylalanine and threonine. With the increasing dietary CP levels, lysine contents appeared constantly; methionine appeared quadrticly decreased (Q; P<0.05); histidine and the branch-chain AA were quadraticly increased (Q; P<0.05). The AAs which concentration was lower in diets than in bacterial proteins may play a key role in regulation of rumen microbial protein synthesis.更多还原