【作者】 屠焰；

【导师】 刁其玉；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2011， 博士

【摘要】 本文以早期断奶犊牛为研究对象,通过4部分试验系统地研究了代乳品酸度及代乳品中酸度调节剂(Acidity regulator)对早期断奶犊牛生长性能、营养物质表观消化率、血液生化指标及部分免疫指标、血气指标、肠道微生物菌群、瘤胃及小肠黏膜形态的影响。试验一、代乳品原料系酸力和pH值对代乳品相应指标的影响选用代乳品专利ZL 02 128844.5中标明的10类原料,以正交试验方法配制成代乳品原料混合物,测定原料、混合物的系酸力和pH值,并采用多元回归方法进行统计分析。结果表明,在本试验设计范围内,仅以系酸力和pH值为指标时,代乳品原料混合物中各原料的适宜添加比例为:特制大豆35%~60%,乳清粉≥30%,蛋氨酸盐酸盐≤0.5%,赖氨酸盐酸盐≤0.5%,碳酸钙比例尽可能降低,磷酸氢钙1%,维生素预混料0~0.02%,食盐1.0%。结果表明,犊牛代乳品系酸力或pH值分别与所用原料的配比和系酸力或pH值之间存在显著的多元线性回归关系。试验二、代乳品酸度对哺乳期犊牛生长性能、营养物质消化代谢、血液指标及胃肠道发育的影响采用双因子试验设计,2个因子为:代乳品乳液的pH值(6.2、5.5、5.0、4.5)和代乳品中植物源性蛋白占总蛋白的比例(50%和80%),共分8个处理。选用48头新生中国荷斯坦公犊牛,随机分成8组,分别饲喂上述8种日粮。试验期内第25至27 d、53至55 d进行两期消化试验。63 d试验结束时每组选取3头犊牛进行屠宰试验。结果表明,适当降低代乳品乳液pH值可通过改善犊牛血液指标、胃肠道黏膜形态和发育情况,提高犊牛对日粮部分营养物质的消化率,降低腹泻的发生,从而改善哺乳期犊牛生长性能。根据本试验各项指标的测定结果及实际饲用效果,哺乳期犊牛代乳品乳液的pH值以调整到5.0为宜。试验三、代乳品中复合酸度调节剂配方的筛选采用1%酸溶液pH值及其缓冲性能、降低代乳品pH值至5.0所需的酸的体积、加酸后代乳品缓冲性能、大肠杆菌体外抑菌率5个参数作为体外试验指标。试验分为两个部分。其一是单体酸的体外试验,分别测定甲酸、乙酸、柠檬酸、富马酸、乳酸、盐酸的各项指标。每种酸为一个处理,每个处理5个重复。其二是复合酸配方筛选试验,采用配方均匀设计方法,以甲酸、乙酸、柠檬酸、富马酸、乳酸、盐酸作为酸度调节剂最佳配伍主料,按照均匀设计表中U20*(206)有约束配方设计、以6因素安排均匀设计试验,把6种酸组合成20个处理,每个处理5个重复。对多个指标进行逐步回归分析,求综合因变量最优解。结果表明,盐酸和甲酸的效果最佳。以配方均匀设计方法筛选出的复合酸度调节剂最佳实验室理论配方为,甲酸40.74%、盐酸50.62%、柠檬酸8.64%。本试验中设定的评价指标皆与参试酸在复合酸度调节剂中比例具有显著的二次回归关系,这5个参数可作为体外评价犊牛代乳品酸度调控的指标。试验四、酸度调节剂对哺乳期犊牛生长性能、营养物质消化率及血气指标的影响选取24头新生中国荷斯坦公犊,分为对照组和3个试验组。对照组犊牛饲喂常规代乳品乳液,其pH值为6.2,试验组代乳品乳液中分别添加甲酸、复合酸,使其pH值降低到5.0。每个处理6个重复,每个重复1头牛。试验期内进行两期消化试验。结果表明,在本试验条件下,酸度调节剂对于饲喂后28 d前的犊牛作用较大,主要表现在改善犊牛血气指标,降低腹泻发生率,提高生长性能,其中复合酸对犊牛ADG、F/G的作用最优,而甲酸对肠道微生物的调节作用更加显著。在饲喂植物蛋白占总蛋白80%、添加酸度调节剂使乳液pH值降低到5.0的代乳品时,犊牛的ADG可达到饲喂植物蛋白占总蛋白50%未酸化代乳品的犊牛的水平。本文得出以下结论:⑴将代乳品乳液pH值降低到适宜范围,可通过改善犊牛、特别是饲喂28 d之前犊牛的血液指标、胃肠道黏膜形态和发育情况,提高犊牛对日粮某些营养物质的消化率,降低腹泻的发生,从而改善哺乳期犊牛生长性能;⑵对于我国的犊牛品种和用植物蛋白制备的代乳品,代乳品乳液的pH值以调整到5.0为宜;⑶提出了体外筛选复合酸配方的5个指标参数,即1%酸溶液pH值及其缓冲性能、降低代乳品pH值至5.0所需的酸的体积、加酸后代乳品缓冲性能、大肠杆菌体外抑菌率,建立了体外评价犊牛代乳品复合酸的方法。更多还原

【Abstract】 Four trials were conducted with pre-ruminant calves as animal models to study the effect of acidity acidity regulators in a milk replacer on the calves’growth performance, digestibility of nutrients, blood biochemical parameters and gastrointestinal characteristics.Experiment 1: Effects of the acid-binding capacity and pH values of ingredients of a calf milk replacer on its relevant characteritics of acidityThis experiment was conducted to study the effect of the content and acid binding capacity (ABC) or pH value of ingredients of a calf milk replacer on its ABC or pH value. Ten feed ingredients indicated in a Chinese patent for a calf milk replacer were chosen to produce the calf milk replacer according to an L27(313) orthogonal design. The ABC and pH value of both the ingredients and the milk replacer were determined, and then a multiple regression method was used to analyze the data. The results showed that the proper content of each ingredient in the calf milk replacer was as follows: specially treated soybean, 35-60%; whey powder,≥30%; L-methionine hydrochlorate,≤0.5%; L-lysine hydrochlorate,≤0.5%; CaCO3, minimum; CaHPO4, about 1%; vitamin premix, 0-0.02%; NaCl, about 1.0%. There were significantly multiple linear correlations between the ABC or pH of the calf milk replacer and the content, ABC or pH of its ingredients.Experiment 2: Effects of the acidity of a milk replacer on growth performance, digestibility of nutrients, blood parameters and gastrointestinal characteristics in pre-ruminant calves The pH values of a milk replacer (6.2, 5.5, 5.0 or 4.5) and the ratio of vegetable protein to total protein in the milk replacer (50 or 80%) were used to form a 4×2 factorial design in this experiment. Forty eight neonatal healthy Holstein male calves were allotted to eight groups and each group was fed with one of the 8 milk replacers. The experiment lasted for 56 d. A digestion trial was conducted in 2 stages of 25-27 d and 53-55 d. Three calves of each group were slaughtered at the end of experiment. The results showed that the calves fed the milk replacer with an appropriate pH value had improved blood parameters and development of the gastrointestinal tract, enhanced nutrient digestibility and growth performance, decreased diarrhea incidence. The optimal pH value of the calf milk replacer was found to be 5.0.Experiment 3: Screening of the formula of compound acidity regulators for a calf milk replacerAn in vitro experiment was conducted with six candidate acidity regulators to measure their antibacterial activity in vitro (Y1), pH value of 1% solution (Y2), buffering capacity of 1% solution (Y3), the volume of acid solutions to reduce the pH value of a milk replacer to 5.0 (Y4), and the buffering capacity of the milk replacer solution with added acids (Y5). There were two parts in the experiment. One was to test the individual acid. The parameters Y1 to Y5 of formic acid,acetic acid, citric acid, fumaric acid, lactic acid and hydrochloric acid were determined respectively with five replicates each. The other part was to screen the formula of compound acidifying agents. Formic acid, acetic acid, citric acid, fumaric acid, lactic acid and hydrochloric acid were used as ingredients according to a formula uniform design table U20*(206). There were twenty treatments with five replicates each. A stepwise multiple regression method was used to analyze the data, and then the optimal compound solution was chosen. The results showed that formic acid and hydrochloric acid were the best acidity regulators, and the optimal formula of compound acidity regulator was 40.74% formic acid, 50.62% hydrochloric acid and 8.64% citric acid. A significantly quadratic relationship existed between five indices (Y1 to Y5) and tested acids.Experiment 4: Effects of acidity regulators in a milk replacer on growth performance, digestibility of nutrients and blood biochemical parameters in pre-ruminant calvesTwenty four neonatal healthy Holstein male calves were allotted to four groups, and one group was fed with a normal milk replacer with a pH value of 6.2 (Group F1), the others were fed with the milk replacer after reducing its pH value to 5.0 by adding formic acid (Group F3) and compound acidity regulator (Group F2 and F4), respectively. The ratios of vegetable protein to total protein in the milk replacer were 50% (Group F1, F2 and F3) or 80% (Group F4). The digestion trial was conducted twice during the trial. The results showed that acidity regulators played an important part in the milk replacer fed to the calves less than 28 d, as exhibited by improved blood biochemical parameters, lowered incidence of diarrhea, and enhanced growth performance of the calves. Adding formic acid in the milk replacer significantly lowered the count of bacteria in the calves’rectum feces when compared with the compound acidity regulator. The ADG of the calves fed with the milk replacer of pH 5.0 and containing 80% vegetable protein was similar to that of those fed with the milk replacer of pH 6.2 and containing 50% vegetable protein.In conclusion, pre-ruminant calves fed with a milk replacer with a properly lowered pH value showed improved blood parameter and development of the gastrointestinal tract, improved nutrient digestibility, lowered diarrhea incidence, and enhanced growth performance. The optimal pH value of the calf milk replacer containing vegetable protein was found to be 5.0. The in vitro method used in this study was capable of evaluating compound acidity regulators.更多还原