【作者】 常娟；

【导师】 尹清强；

【作者基本信息】 河南农业大学 ， 动物营养与饲料科学， 2011， 博士

【摘要】 目前,能量饲料的短缺是世界各国面临的一个重大问题。中国是世界上秸秆产量最多的国家,秸秆产量占中国生物质资源的一半,经济有效地利用秸秆能够实现可再生资源的利用,缓解能源危机,保护环境,实现农业和经济的可持续发展。随着动物生产中最主要的能量饲料——玉米价格的上涨,切实可行地将木质纤维类物质转化为动物饲料已迫在眉睫。本文将秸秆的预处理与微生物发酵相结合,研制出高效的生物发酵秸秆饲料,并进行工厂化生产,研究其营养价值和代替玉米对肉鸡生产性能的影响,结果表明:(1)对玉米秸秆进行不同物理化学预处理的研究表明,玉米秸秆预处理的最优条件为:风干玉米秸秆在压力2.5 Mpa,保压时间200 s的条件下直接进行爆破处理,蒸汽爆破使秸秆中纤维素、半纤维素和木质素的降解率分别达到8.47%、50.45%和36.65%(P<0.05)。选择该条件进行预处理,在实际生产中是可行的,为后续微生物发酵奠定了基础。(2)首先对玉米秸秆进行蒸汽爆破预处理(2.5 Mpa, 200 s),然后再进行不同微生物发酵,研究物理和生物学处理对秸秆成分、相关酶活和微观结构的影响。结果表明,两种微生物发酵均显著降低了秸秆中的纤维素含量(P<0.05),米曲霉在降解爆破秸秆中的中性洗涤纤维和酸性洗涤纤维方面的效果显著高于康氏木霉(P<0.05),说明米曲霉发酵更有利于秸秆中不溶性纤维成分的转化。爆破预处理秸秆经米曲霉发酵6 d后,秸秆中纤维素和半纤维素的降解率分别为27.89%和64.80%(P<0.05),发酵秸秆中的滤纸酶、羧甲基纤维素酶、淀粉酶和蛋白酶活力分别达到335.10、1138.92、32.57和201.99 U/g。爆破秸秆经米曲霉发酵后,甲酸含量降低,糠醛全部被降解,有效地减少了爆破产物对动物生产可能产生的潜在负面影响。扫描电镜对微观结构的观察表明,未处理秸秆的表面规则平滑,紧密完整。爆破处理后的秸秆表面有许多球形的凸起结构,使秸秆中的木质素发生重排,提高了秸秆的比表面积。爆破秸秆经微生物发酵后,机械组织破碎,内部有更多的纤维组织暴露,更有利于动物对纤维成分的利用。爆破预处理和米曲霉发酵相联合,对于提高玉米秸秆的降解率具有非常重要的意义。(3)以爆破玉米秸杆为主要原料(81-100%),以玉米(0、2.5、5.0%)、麸皮(0、2.5、5.0%)、豆粕(0、2.5、5.0%)和复合营养物质(0、2.0%、4.0%)设计四因素三水平正交试验,对爆破秸秆微生物发酵的培养基进行优化,正交试验结果表明爆破秸秆生物降解的最优培养基组合为:83.5%爆破玉米秸杆、5.0%玉米、2.5%麸皮、5.0%豆粕和4.0%营养液。其中营养液、豆粕和玉米的不同水平对纤维素的降解率有显著的影响(P<0.05)。(4)分别采用套算法和强饲法测定生物秸秆肉鸡的表观代谢能。套算法选用16只AA商品肉鸡,分为2个处理,每个处理8只鸡。处理1饲喂基础日粮(基础日粮中添加了8%的生物秸秆),处理2饲喂试验日粮(以30%的生物秸秆代替基础日粮中的能量饲料和蛋白质饲料)。计算出基础日粮的肉鸡表观代谢能12.63 MJ/Kg,推算出生物秸秆的表观代谢能为12.46 MJ/kg,而根据套算法计算出生物秸秆的表观代谢能为4.38 MJ/Kg。强饲法选用10只AA商品肉鸡,分为2个处理,每个处理5只鸡。处理1饲喂生物秸秆,处理2饲喂爆破秸秆。计算出生物秸秆和爆破秸秆对肉鸡表观代谢能分别为5.30和6.33 MJ/kg。(5)为研究生物秸秆替代玉米的适宜比例及生物秸秆对肉鸡生产性能和各项指标的影响,对肉鸡进行前期(1～21 d)和后期(22～42 d)两个阶段的饲养试验。前期选择1日龄健康的AA肉仔鸡200只鸡,分为5处理,每个处理4个重复,每个重复10只鸡。后期在前期原处理内共选择150只鸡,分为5个重复,每个重复6只鸡。对照组饲喂基础日粮,试验1组用生物秸秆代替基础日粮中4%的玉米(ME按照推算法计算结果12.46 MJ/kg计),试验2组用生物秸秆代替基础日粮中8%的玉米(ME按照推算法计算结果12.46 MJ/kg计),试验3组用生物秸秆代替基础日粮中12%的玉米(ME按照推算法计算结果12.46 MJ/kg计),试验4组用生物秸秆代替基础日粮中8%的玉米(ME按照强饲法计算结果5.30 MJ/kg计,各项营养指标与对照组平衡)结果表明:在试验前期,饲料中添加各水平的生物秸秆均降低了肉鸡的日增重和饲料转化效率。12%的生物秸秆添加组和对照组相比显著降低了肉鸡对有机物质、能量和蛋白质的代谢率(P<0.05),显著降低了肉鸡回肠和盲肠的乳酸菌数量(P<0.05);12%的生物秸秆添加组和8%的生物秸秆加油组显著提高了肉鸡的血清尿酸的水平(P<0.05);饲料中添加12%的生物秸秆对肉鸡性能有显著的负面影响。8%生物秸秆添加组肉鸡十二指肠滤纸酶和CMC酶、盲肠的滤纸酶显著高于其它各组(P<0.05),添加8%的生物秸秆代替玉米更有利于纤维素酶活力的增加和肉鸡对饲料中纤维成分的消化。不同比例的生物秸秆代替玉米均降低了肉鸡饲养的经济效益。在试验后期,饲料中添加4%和8%的生物秸秆代替玉米和对照组相比显著提高了肉鸡的采食量(P<0.05),其中8%组肉鸡日增重比对照组提高5.75%;4%和8%的生物秸秆代替玉米组饲料中中性洗涤纤维和酸性洗涤纤维的代谢率显著高于对照组(P<0.05);8%生物秸秆代替玉米组肉鸡回肠和盲肠中的乳酸菌高于对照组(P<0.05),该组肉鸡十二指肠和盲肠的滤纸酶、CMC酶均显著高于对照组(P<0.05)。饲料中添加12%的生物秸秆和对照组相比显著降低了肉鸡能量的代谢率(P<0.05);12%的生物秸秆添加组肉鸡回肠和盲肠的乳酸菌显著低于8%的生物秸秆代替玉米组(P<0.05);饲料中添加12%的生物秸秆代替玉米显著提高了肉鸡十二指肠和回肠的相对重量(P<0.05)。8%的生物秸秆能量平衡组显著提高了血清总蛋白、白蛋白和球蛋白的水平(P<0.05),提高了蛋白质的利用效率;8%的生物秸秆能量平衡组肉鸡回肠和盲肠中的乳酸菌高于对照组(P<0.05);8%的生物秸秆能量平衡组使肉鸡胸肌的红度升高,提高肉的品质。在肉鸡后期饲料中添加4%的生物秸秆代替玉米,提高了肉鸡的经济效益,添加8%的生物秸秆代替玉米,经济效益和对照组相当,饲料中添加8%的生物秸秆代替玉米经济效益高于8%的生物秸秆能量平衡组。因此,在肉鸡饲养后期的饲粮中添加4-8%的生物秸秆代替玉米有利于肉鸡生产性能和经济效益的提高,对于农作物秸杆的利用及节粮型畜牧业的发展具有重要意义。更多还原

【Abstract】 Energy feed shortage is a major problem all over the world. China is the leading crop straw producer in the world, and the straw yield accounts for half of the biomass resources. It can realize the use of renewable resources, relieve the energy resources crisis, protect the environment and realize the sustainable development of agriculture and economy by the economic and effective utilization of straw. With the rising price and shortage of corn, the main energy feed in animal production, it is imminent to convert straws into animal feed.In this study, the pretreatment and microbial fermentation was combined in developing the biological fermentation of corn stalk (BFCS). Study on its nutritional value and effect on production performance of broiler was conducted. The results were as follows:(1) The effect of different physical and chemical pretreatments on corn stalk degradation was studied. The results showed that the optimum condition of corn stalk pretreatment was air dry corn stalk exploded directly under 2.5 Mpa pressure for 200 s. The degradation rates of cellulose, hemicelluloses and lignin in the corn stalk were 8.47%, 50.45% and 36.65%, respectively. The pretreatment was practical and suitable for the subsequent microbial fermentation.(2) To study the combined effect of physical and biological treatments on corn stalk degradation, microstructure, composition and enzyme productions, the corn stalk was steam exploded (2.5 Mpa, 200 s), and then followed by microbial fermentation. The results showed that microbial fermentation could reduce the contents of cellulose in original and exploded stalks significantly (P<0.05). NDF and ADF contents in the exploded corn stalk fermented by Aspergillus oryzae was significantly lower than that fermented by Trichoderma koningii (P<0.05), which indicated Aspergillus oryzae fermentation was more effective than Trichoderma koningii for the insoluble fiber degradation. After the exploded corn stalk was fermented by Aspergillus oryzae for 6 days, the contents of cellulose and hemicellulose in the fermented corn stalk were decreased by 27.89% and 64.80% respectively, compared with the original corn stalk (P<0.05). The filter paper cellulase, CMCase, amylase and protease activities in the fermented products were 335.10, 1138.92, 32.57 and 201.99 U/g, respectively. The content of formic acid in the fermented products was lower than that in the exploded stalk, and furfural in the fermented products was all degraded, which indicated that fermentation treatment effectively reduced the content of inhibitors produced in the pretreatment. The microstructure was analyzed by scanning electron microscope, the surface of untreated corn stalk was smooth and tightly complete. There were many spherical structures on the surface of exploded corn stalk, indicating explosion treatment made the lignin in corn stalk rearrangement to increase the specific surface area. The fermentation of exploded corn stalk by Aspergillus oryzae made the tissues broken, and more internal fibrous exposed, which contributed to the utilization of animals. The corn stalk pre-treated by steam explosion and followed by Aspergillus oryzae fermentation seems to be a new prospective method for corn stalk degradation and application.(3) The four-factor and three-level orthogonal experiment was used to determine the optimum fermentation prescription of exploded corn stalk. The result showed that the optimal medium for biodegradation of exploded corn stalk was 5% corn meal, 2.5% wheat bran, 5% soybean meal and 4% the nutrient solution. The levels of nutrient solution, corn, and soybean had significant effect on stalk degradation (P<0.05).(4) Substitution method and emptying-force-feeding method were used to determine the apparent metabolic energy of BFCS separately. In substitution method, a total of 16 AA broilers were assigned to 2 groups, 8 broilers for each group. Group 1 was fed with the basal diet (consist of 8% BFCS); group 2 was added with 30% BFCS to replace the same percent of energy and protein feed in the basal diet. The results showed that the apparent metabolic energy (AME) of broiler in basal diet is 12.63 MJ/kg, AME of BFCS predicted by the formulation of basal diet was 12.46 MJ/kg,which was 4.38 MJ/Kg calculated by the formula. In emptying-force-feeding method, a total of 10 AA broilers were assigned to 2 groups, 5 broilers for each group. Group 1 was added with the BFCS; and group 2 was added with exploded corn stalk. The result showed that AME of broilers in group1 and group 2 was 5.30 and 6.33 MJ/kg, respectively.(5) A 2-period feeding program was adopted in the experiment to study the effect of BFCS for replacing corn meal on broiler production, and to get the suitable substitution rate for broiler farming.In the earlier stage (1-21 d), a total of 200 one-day-old AA broilers were assigned to 5 groups, 40 broilers for each group consisting of 4 replicates. In the later stage (22-42 d), a total of 150 22-day-old AA broilers were assigned to 5 groups, 30 broilers for each group consisting of 5 replicates. The control group was the basal diet; group 1, 2 and group 3 was added with 4%, 8% and 12% BFCS for replacing the same percent of corn meal in the basal diet, respectively. Group 4 was added with 8% BFCS for replacing the same percent of corn meal in the basal diet, and the energy was balanced with the control.In the earlier stage, the results showed that the average daily gain (ADG) and the feed conversation (FCR) were decreased significantly in the groups added with BFCS (P<0.05); the organic matter, energy and protein metabolic rates in group 3 were lower than that in the control group (P<0.05). The counts of lactic acid bacteria in the ileum and cecum in group 3 was reduced, compared with the control group (P<0.05). The serum uric acid content in group 3 and 4 was higher than that in the control (P<0.05). The activities of filter paper enzyme, CMC enzyme in duodenum and the filter paper enzyme in cecum in group 2 were higher than that in the other group (P<0.05). Economic benefit of the groups added with BFCS were reduced, compared with the control.In the later stage, the feed intake was improved in group 1 and group 2 (P<0.05); metabolic rate of NDF and ADF in group1 and group 2 were significantly higer than that in the control group (P<0.05); lactic acid bacteria counts in ileum and cecum of group 2 was increased significantly (P<0.05). The activities of filter paper and CMC enzymes in duodenum and cecum in group 2 were higher than that in the control group (P<0.05). The average daily gain (ADG) was improved in group 2, 3 and 4 (P<0.05); the energy metabolic rate was reduced in group 3 (P<0.05); lactic acid bacteria counts in ileum and cecum of group 3 were significantly lower than that in group 2 (P<0.05); relative weight of duodenal and ileum were improved in group 3. The serum total protein, albumin and globin were improved in group 5 (P<0.05), lactic acid bacteria counts in ileum and cecum were increased significantly in group 5 (P<0.05), the red degree of pectorals in group 5 was also increased. The economic benefit in group 1 was higher than that in the control group, the economic benefit in group 2 was comparable to that in the control, and was higher than that in group 4.In conclusion, 4-8% BFCS to replace corn meal in the diets of broilers at later feeding stage could improve production performance of broilers, and the application of BFCS in animal production is an economic and feasible way.更多还原