Subjects: Biology >> Zoology submitted time 2018-12-25 Cooperative journals: 《动物营养学报》
Abstract：本试验旨在研究米曲霉来源α-半乳糖苷酶基因gal A在毕赤酵母中的表达及其对豆浆中大豆寡糖的酶解效果。以NCBI数据库中米曲霉来源α-半乳糖苷酶基因gal A的mRNA序列（GenBank登录号：XP_001817311.1）为依据，利用PCR扩增得到gal A基因并根据毕赤酵母使用密码子的偏好性优化基因序列，构建野生型和优化型毕赤酵母工程菌株，摇瓶发酵 120 h，测定酶学性质。设置25和45 ℃2个温度，每个温度下各设置0.6、1.2和2.4 U 3个加酶量，用发酵得到的α-半乳糖苷酶酶解10 mL豆浆中的大豆寡糖。结果显示：该α-半乳糖苷酶基因gal A全长1 605 bp，不含内含子，编码534个氨基酸，诱导120 h后优化型工程菌株的α-半乳糖苷酶活性为1.952 U/mL，比野生型工程菌株提高了285%。发酵得到的α-半乳糖苷酶的最适pH为4.33，最适温度为55 ℃；在pH 3.00~8.00间稳定性良好，在55 ℃条件下保持40 min后残余α-半乳糖苷酶相对活性为60%；该酶对大部分金属离子具有抗性，但其被MnSO4抑制；以pNPG为底物时的酶动力学参数米氏常数（Km）为0.024 3 mol/L，最大反应速度（Vmax）为1.0×10-7 mol/(L·s)。酶解试验结果显示，45 ℃下加酶量为2.4 U反应12 h后，大豆寡糖中棉籽糖的降解率为50.0%，水苏糖的降解率为31.9%。由此可见，本试验中生产的α-半乳糖苷酶对豆浆中的大豆寡糖有一定的降解作用。
Subjects: Biology >> Zoology submitted time 2017-10-11 Cooperative journals: 《动物营养学报》
Abstract：本试验旨在研究饲粮中不同粗蛋白质水平对“京红1号”蛋鸡产蛋后期生产性能和蛋品质的影响，以确定其适宜蛋白质水平。试验选用41周龄“京红1号”商品代蛋鸡720只，按实测粗蛋白质水平（分别为14.08%、14.53%、14.98%和15.44%）随机分为Ⅰ组、Ⅱ组、Ⅲ组和Ⅳ组，每组12个重复，每个重复15只鸡。预试期1周，正试期22周。结果表明：1）饲粮粗蛋白质水平对蛋鸡产蛋率、平均蛋重和日产蛋量影响显著（P<0.05），且其均随饲粮粗蛋白质水平升高线性增加（P<0.05）；饲粮粗蛋白质水平对蛋鸡料蛋比影响显著（P<0.05），且其随粗蛋白质水平升高线性降低（P<0.05）。2）Ⅳ组蛋壳厚度显著高于Ⅰ组和Ⅲ组（P<0.05）；Ⅳ组蛋重显著高于Ⅰ组和Ⅱ组（P<0.05），蛋重随着饲粮粗蛋白质水平升高线性增加（P<0.05）。3）经济效益分析表明Ⅳ组蛋重成本最低，经济效益最佳。综合生产性能与经济效益分析，42~64周龄“京红1号”蛋鸡适宜粗蛋白质水平为15.44%，适宜蛋白能量比为13.41 g/MJ。
Subjects: Biology >> Zoology submitted time 2017-10-10 Cooperative journals: 《动物营养学报》
Abstract： The research was conducted to investigate the effects of different dietary crude protein (CP) level on performance and egg quality of Jinghong laying hens during late stage of egg production, and to obtain optimum protein proportion for them. A total of 720 Jinghong laying hens aged at 41 weeks were randomly divided into groups Ⅰ, Ⅱ, Ⅲ and Ⅳ with 12 replicates per group and 15 hens per replicate. The CP level in diets of four groups was 14.08%, 14.53%, 14.98% and 15.44%, respectively. The adaptation period was 1 week, and the experimental period was 22 weeks. The results showed as follows: 1) there was significant difference in laying rate, average egg weight and daily egg production (P<0.05) among different dietary CP levels, and all of them were increased linearly with dietary CP level increasing (P<0.05). Besides, there was significant difference in the ratio of feed to egg (P<0.05) among different dietary CP levels, and the ratio of feed to egg was decreased linearly with the increase of dietary CP level (P<0.05). 2) Eggshell thickness in group Ⅳ was significantly higher than that of group Ⅰ and group Ⅲ (P<0.05). Compared with groups Ⅰ and Ⅱ, egg weight in group Ⅵ was significantly higher (P<0.05), and egg weight was increased with the increasing of dietary CP level (P<0.05). 3) Economic analysis showed that the egg weight cost of group Ⅵ was the lowest and got the best economic benefit among all groups. In conclusion, 15.44% (CP/energy was 13.41 g/MJ) is recommended as the best CP level for Jinghong laying hens with 42 to 64 weeks of age.
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