哺乳犊牛的消化特点与蛋白质需要

本文从犊牛的消化生理特点出发,综述了犊牛出生后的生理特征及蛋白质、必需氨基酸的需要量,并对代乳品中蛋白质原料进行了论述。     

代乳粉用于早期断奶犊牛的效果研究

犊牛使用代乳品可以节省鲜奶，降低饲养成本，控制疾病的发生，促进消化系统的发育。试验用24头犊牛做试验，60日龄断奶。结果表明，代乳品组犊牛增重47．55千克；对照组增重41．72千克；吃代乳品的犊牛在30-60日龄的日增重达到1026克，高于对照组103克。吃代乳品的犊牛每增重1千克的直接饲料成本为15．13元，比鲜奶组犊牛低2．14元／千克。     

茶黄酮对无角多赛特羊生长和呼吸道疾病的影响

选择平均体重为26．6kg的无角多赛特断奶大羔羊22只．平均体重为49．3kg的无角多赛特育成羊48只，分别分为对照组和试验组，试验组羊只精料补充料中添加300mg／kg的茶黄酮，研究茶黄酮对羊只生长和呼吸道疾病的影响。结果表明，添加茶黄酮可提高羔羊和育成羊的增重效果．和对照组比较羔羊提高增量9．8%（P〉0．05），育成羊提高增重6．1%（P〉0．05）；在饲料中添加茶黄酮可使羔羊呼吸道疾病发病率降低64%，使育成羊呼吸道疾病发病率降低50%，可有效预防羊的呼吸道疾病。     

棘孢木霉葡聚糖酶基因Glu1的克隆及原核表达

从棘孢木霉(Trichoderma asperellum)ACCC30536中克隆获得一个葡聚糖酶基因Glu1,其cDNA全长984bp,编码327个氨基酸。该葡聚糖酶属于Glyco-hydro-12家族,推测为β-1,4-葡聚糖酶,与深绿木霉IMI 206040的Glycohydro-12家族蛋白(XP_013940397.1)有91%相似性,且亲缘关系较近。运用qRT-PCR技术检测9种诱导条件下棘孢木霉Glu1基因的表达水平,结果表明,Glu1基因能参与棘孢木霉对山新杨(Populus davidiana×P.alba var.pyramidlis)或杨树病原菌的识别。构建原核表达载体并获得重组蛋白rGlu1。酶活特性分析结果表明,该酶最适pH为4.5,最适温度为45℃,且酶活性随诱导时间延长逐渐升高,在5h达到稳定。     

快速型黄羽肉鸡饲料利用效率性状的基因组选择研究

旨在探究快速型黄羽肉鸡饲料利用效率性状的遗传参数,评估不同方法所得估计育种值的准确性。本研究以自主培育的快速型黄羽肉鸡E系1 923个个体（其中公鸡1 199只,母鸡724只）为研究素材,采用"京芯一号"鸡55K SNP芯片进行基因分型。分别利用传统最佳线性无偏预测（BLUP）、基因组最佳线性无偏预测（GBLUP）和一步法（SSGBLUP）3种方法,基于加性效应模型进行遗传参数估计,通过10倍交叉验证比较3种方法所得估计育种值的准确性。研究性状包括4个生长性状和4个饲料利用效率性状：42日龄体重（BW42D）、56日龄体重（BW56D）、日均增重（ADG）、日均采食量（ADFI）和饲料转化率（FCR）、剩余采食量（RFI）、剩余增长体重（RG）、剩余采食和增长体重（RIG）。结果显示,4个饲料利用效率性状均为低遗传力（0.08~0.20）,其他生长性状为中等偏低遗传力（0.11~0.35）;4个饲料利用效率性状间均为高度遗传相关,RFI、RIG与ADFI间为中度遗传相关,RFI与ADG间无显著相关性,RIG与ADG间为低度遗传相关。本研究在获得SSGBLUP方法的最佳基因型和系谱矩阵权重比基础上,比较8个性状的估计育种值准确性,SSGBLUP方法获得的准确性分别比传统BLUP和GBLUP方法提高3.85%~14.43%和5.21%~17.89%。综上,以RIG为选择指标能够在降低日均采食量的同时保持日均增重,比RFI更适合快速型黄羽肉鸡的选育目标;采用最佳权重比进行SSGBLUP分析,对目标性状估计育种值的预测性能最优,建议作为快速型黄羽肉鸡基因组选择方法。     

Effect of urea supplementation on performance and safety in diets of Dorper crossbred sheep

This study was conducted to evaluate the efficacy and safety of dietary urea in sheep rations having a 50:50 concentrate:roughage ratio. Sixty‐four Dorper × thin‐tailed Han crossbred ram lambs with an average body weight of 30.8 (±0.02) kg were randomly divided into four groups of 16 sheep each, and each group was fed one of the following diets: a basal diet (CON), or CON supplemented with 0.5% (0.5UTM), 1.5% (1.5UTM) or 2.5% (2.5UTM) urea. Growth performance, carcass characteristics, non‐carcass offals, meat quality and peptic tissue lesions were assayed. The average daily weight gains for CON, 0.5UTM, 1.5UTM and 2.5UTM were 216, 218, 200 and 170 g, respectively, with the CON and 0.5UTM groups higher than 2.5UTM group (p < 0.05). Sheep from the 2.5UTM treatment had a significantly lower dry matter intake (1.29 kg/day) than those from the CON and 0.5UTM treatments (1.42 and 1.43 kg/day, p < 0.05), and the feed conversion ratio in the 2.5UTM group was the highest (p < 0.05). Carcass characteristics, including shrunk body weight, empty body weight, hot carcass weight, dress percentage, and the absolute or relative weight (% body weight) of heart, liver, spleen, lung and kidney, were not altered by the treatments (p > 0.05). The muscular pH of 2.5UTM was higher than that of CON (5.68 vs. 5.52, p < 0.05), and shear force in 0.5UTM was lower compared with CON and 2.5UTM (p < 0.05). The anatomical structure lesions in kidneys became more serious with the increasing dietary urea concentrations, with the 2.5UTM animals showing the most severe lesions compared with CON animals. Therefore, supplementary urea as a non‐protein nitrogen source for sheep should not exceed 1.5% of ration having a 50:50 concentrate:roughage ratio to ensure efficacy and safety.     

Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens

OBJECTIVE: To investigate the development of enrofloxacin resistance among Escherichia coli isolates obtained from chickens by determining mutant-prevention concentrations (MPCs) and sequence the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes in selected isolates. SAMPLE POPULATION: 15 chicken-derived E coli isolates. PROCEDURES: For all isolates, MPC and minimal inhibition concentration (MIC) of enrofloxacin were determined. The MPCs and maximum serum drug concentrations attained with enrofloxacin doses recommended for treatment of E coli infections in chickens were compared. Mutation frequencies and QRDR sequence changes in gyrA and parC were also determined. RESULTS: In 2 of 15 E coli strains, MPCs were low (0.016 and 0.062 microg/mL), MPC:MIC ratios were 2 and 4, and the GyrA and ParC proteins had no mutations. In 9 susceptible isolates with a GyrA point mutation, MPCs ranged from 2 to 16 microg/mL. For isolates with double mutations in GyrA and a single mutation in ParC, MPCs were > 32 microg/mL (several fold greater than the maximal plasma concentration of enrofloxacin in chickens); mutation frequencies were also much lower, compared with frequencies for single-mutation isolates. CONCLUSIONS AND CLINICAL RELEVANCE: For E coli infections of chickens, MPC appears to be useful for determining enrofloxacin-dosing strategies. The high MPC:MIC ratio may result in enrofloxacin-treatment failure in chickens infected with some wild-type gyrA E coli isolates despite the isolates' enrofloxacin susceptibility (MICs 0.125 to 1 microg/mL). For infections involving isolates with high MPCs, especially those containing mutations in gyrA and parC genes, treatment with combinations of antimicrobials should be adopted.     

基于KPCA-WLSSVM的建筑能耗预测模型

为降低建筑能耗影响因素间复杂相关性对模型性能的影响,建立了一种基于KPCA-WLSSVM的建筑能耗预测模型。利用核主元分析(KPCA)对输入变量进行数据压缩,消除变量之间的相关性,简化模型结构;进一步采用加权最小二乘支持向量机(WLSSVM)方法建立建筑能耗预测模型,同时结合一种新型混沌粒子群-模拟退火混合优化(CPSO-SA)算法对模型参数进行优化,以提高模型的预测性能及泛化能力。通过将KPCA-WLSSVM模型方法应用于某办公建筑能耗的预测中,并与WLSSVM、LSSVM及RBFNN模型相比,实验结果表明,KPCA-WLSSVM模型方法能有效提高建筑能耗预测精度。     

土壤水分对稻米外观品质的影响

水稻的分蘖期、长穗期、抽穗后1～10d、11～20d、21～30d及1～30d,用负压式土壤湿度计监测,分别进行土壤水势为-30～-35kPa、-60～-65kPa的控水处理,收获后对优势粒、中位粒、劣势粒进行粒形和垩白测定,发现在不同土壤水分下S品种长穗期和抽穗后1～10d控水显著抑制了籽粒伸长,也不同程度的抑制了籽粒增宽和长厚,以S4处理受抑制的程度最为严重;Y品种主要是长穗期控水显著抑制了粒长、粒宽和粒厚;两品种的多数处理不同程度的提高了粒厚,这在优势粒中更明显;土壤水分对粒长/宽的影响很小。S品种各处理垩白率、垩白度多低于CK,Y品种各处理垩白率、垩白度多高于CK。对两个品种来说长穗期是影响外观品质的主要水分敏感期,节水栽培应从品种选择入手。     

胞外多聚物在污泥颗粒化过程中的作用研究

本文研究了胞外多聚物(ECP)在污泥颗粒化过程中的作用。试验采用小试UASB反应器,以人工葡萄糖配水作为进料。测定结果表明,在颗粒污泥培养过程中,随着颗粒污泥的形成、生长和成熟,污泥ECP含量逐渐下降,从开始的6.36减小到30mg/gVSS。当反应器酸化、污泥性能变差或运行不稳定时,ECP含量则表现为急剧上升,达70mg/gVSS。这些结果说明污泥颗粒化过程中ECP所起的作用不大。对有关ECP的影响及作用机理,以及污泥颗粒化机制,文章进行了分析讨论。