【作者】 李树聪；

【导师】 王加启；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2005， 博士

【摘要】 本研究在调查我国奶牛养殖模式基础上,研究不同精粗比典型日粮蛋白质、氨基酸营养供应和利用状况,分析限制性氨基酸种类和程度,为完善我国奶牛蛋白质营养需要体系,提高奶业生产技术水平,指导和推动奶业健康发展积累经验和数据。 本论文首先利用四头三位点瘘管奶牛研究了简单T型十二指肠瘘管食糜流量监测方法。结果表明通过简单T型瘘管所采集的十二指肠食糜样品不具代表性。可以将食糜分为两到三相,三种指示剂Co-EDTA、YbCl₃和Cr染纤维在不同食糜相中的分布差异显著,Co主要存在于液相食糜中,Yb主要与小颗粒食糜结合,而Cr在大颗粒食糜中含量最高。利用单相指示剂计算食糜干物质流量变异很大,其中Co估测值最低,Yb估测值最高,Cr估测值变异最大,利用两相和三相指示剂估计的流量值处于中等。多相指示剂的使用可显著提高十二指肠酸性洗涤不溶灰分流量估测的准确度。 本论文第二部分主要研究了四种不同精粗比典型日粮条件下泌乳奶牛瘤胃氮素代谢、小肠蛋白质的消化吸收及其对生产性能的影响。试验动物为四头三位点瘘管泌乳奶牛,采用4×4拉丁方试验设计。结果表明粗料为70%羊草的日粮,氮源不足限制了瘤胃微生物生长。不同精粗比日粮瘤胃真可消化有机物（RDOM）生成微生物氮的效率差异不显著,每公斤RDOM可生成29.08g微生物氮。粗料的改善和精粗比的提高显著增加十二指肠非氨氮流量,增加的非氨氮主要是瘤胃微生物氮。四种日粮条件下,进入小肠的微生物氮占总非氨氮的比例为52.8%～62.9%。进入小肠的非氨氮消化率平均为67.70%,在各日粮间差异不显著。泌乳奶牛食入氮中,平均25.61%以粪氮的形式排出,48.56%以尿氮的形式排出。食入氮转化为乳中真蛋白氮和体组织沉积氮的效率随精料水平的提高而提高。乳产量、乳蛋白率随日粮粗料的改善和精料水平的提高而提高。乳蛋白率和小肠非氨氮流量相关显著。 本论文第三部分主要研究了四种不同精粗比典型日粮条件下泌乳奶牛氨基酸营养的供给状况及其对生产性能的影响。试验动物为四头三位点瘘管泌乳奶牛,采用4×4拉丁方试验设计。结果表明日粮精粗比对瘤胃细菌、牛奶氨基酸组成没有影响。除精氨酸外,其他氨基酸小肠消化率在各种日粮间差异不显著（消化率为46.47%～82.98%）。以乳蛋白质氨基酸组成为理想氨基酸模式对小肠可吸收氨基酸进行评价,结果表明赖氨酸、蛋氨酸为四种日粮的主要限制性氨基酸,支链氨基酸重要性仅次于赖氨酸和蛋氨酸。泌乳奶牛在采食3070CW日粮后,血液中必需氨基酸出现累积,非必需氨基酸浓度显著低于其他三种日粮,表明该日粮条件下,泌乳奶牛因能量不足导致必需氨基酸利用率降低。 本论文第四部分以四头三位点瘘管泌乳奶牛为试验动物,利用回撤灌注技术研究了精粗比为50:50的典型日粮条件下,赖氨酸、蛋氨酸和支链氨基酸对泌乳奶牛生产性能影响。试验采用4×4拉丁方设计,通过十二指肠灌注不同组合氨基酸,结果表明回撤赖氨酸后产奶量有降低趋势,乳蛋白率、非脂固形物显著降低。而回撒支链氨基酸对生产性能没有影响,回撤蛋氨酸后乳蛋白率显著降低,但乳蛋白产量等其他指标没有变化。研究发现支链氨基酸和蛋氨酸之间有颉抗作用。除苏氨酸、蛋氨酸和胱氨酸外,乳腺对其他氨基酸的摄取量与动脉血浆中氨基酸浓度存在显著的线性正相关关系。乳腺对动脉血液中必需氨基酸的摄取效率在13%～55%之间。更多还原

【Abstract】 Four cows fitted with permanent rumen cannulas and simple T-type duodenal cannulas were first used to compare the effects of external digesta markers (Co-EDTA, YbC13 and Cr-mordanted straw) and recombined marker systems on the flow of digesta entering the duodenal canal of lactating dairy cows. Samples of digesta got from the duodenal canal were pooled and separated using filtration and highspeed centrifugation into two or three fractions defined as the liquid phase and solid phase (small particulate and large particulate). Co was primarily associated with the liquid phase; Yb was concentrated in small particulate matter, whilst Cr was associated with large particles. The results showed that the samples collected at duodenum were not representative of "true" digesta. Use of single markers resulted in large variance in dry matter flow estimation compared with the combination of two or three markers. The results showed that the combination of two or three markers could increase the accuracy of estimation of the AIA (Acid Insoluble Ash) flow at duodenum.The second part was mainly conducted to study the effects of four typical diets on rumen nitrogen metabolism, protein digestion and absorption in the small intestine, and dairy cow’s milk performance. Four rumen, duodenum and Ileum cannulated cows were used in a 4X4 Latin square experiment design with different forage to concentrate ratios. The growth of rumen bacteria was inhibited due to the shortage of the nitrogen supply in the high forage diet (70% Chinese wildrye and 30% concentrate). There were no significant differences of the conversion of dietary RDOM (Rumen Digestible Organic Matter) into microbial nitrogen among the diets. The efficiency of microbial nitrogen synthesis was 29.08g/kg RDOM. The non-ammonia nitrogen flow at duodenum was increased due to the increment of microbial nitrogen. The ratios of microbial nitrogen to the total nitrogen flow at the duodenum ranged from 52.8% to 62.9% among the four diets. There was no significant difference in the digestibility of the non-ammonia nitrogen (average 67.70+1.91%) entering into the small intestine.The conversion rates of dietary nitrogen into milk nitrogen and deposition nitrogen in the tissue were increased with higher concentrate. Among the total nitrogen intake, about 25.61 % and 48.56% nitrogen were excluded through feces and urine respectively. Milk production and protein content were increased by increasing the quality of the forage and the level of the concentrate in the diet. There was a positive correlation between milk protein content and the non-ammonia flow in the small intestine.The third part was conducetd to compare the effects of four typical diets on the supply of the amino acids in small intestine and utilization of them. Forage to concentrate ratios did not affect the amino acid profiles of rumen bacteria and milk protein. The four diets did not affect the amino acids digestibility (ranged from 46.47% to 82.98%) in small intestine except for Arginine. Based on essential amino acid profile of the milk protein, the small intestinal ideal amino acid model was evaluated in four diets and the results showed that the Lysine and Methionine were the main limited amino acids. BCAA (Branch Chain Amino Acids) were next to them.In the fourth part, four rumen, duodenum and Ileum cannulated cows were used in a 4 × 4 Latin square experiment to compare the effects of duodenum infusing Lysine, Methionine and BCAA on milk更多还原