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。     

Dynamics of Integration between Chinese and International Waste Paper Markets

ABSTRACT

China is the largest importer of waste paper in the world and is highly dependent on the international market. Thus, the relationship between Chinese and international waste paper markets affects the supply of fiber materials in China’s paper industry. This study examined the dynamic relationship between the two markets and the impact of newly implemented policies on both markets. We used unit root tests, cointegration test, vector error correction model (VECM) and frequency-domain Granger causality test to investigate the integration between Chinese and international waste paper markets and identify which of the two markets is the price leader. The results revealed that the two markets were integrated after controlling for structural breaks, and the Chinese market acted as the price leader. Since the supply of waste paper and wood pulp is insufficient in China to meet the fiber demand of the paper industry, waste paper import restrictions have significantly affected the supply of fiber materials in China’s paper industry. Therefore, the Chinese government should fully consider the benefit of market integration and make full use of international waste paper resources to satisfy the large domestic demand for paper products.     

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.     

五个典型柑桔品种的落花落果规律调查

以成年纽荷尔脐橙、兴津温州蜜柑、沙田柚、尤力克柠檬和圆金柑为材料，探索其花果脱落规律。结果表明，最终坐果率与总花量（含花蕾）显著负相关（P < 0.01）；平均单株花果脱落总数量为兴津温州蜜柑 > 纽荷尔脐橙 > 沙田柚 > 圆金柑 > 尤力克柠檬；平均单株花果脱落总干重为兴津温州蜜柑 > 纽荷尔脐橙 > 沙田柚 > 尤力克柠檬 > 圆金柑；纽荷尔脐橙、兴津温州蜜柑和沙田柚第一次生理落果数量大于第二次生理落果，尤力克柠檬和圆金柑第二次生理落果数量大于第一次生理落果。因此，纽荷尔脐橙、兴津温州蜜柑和沙田柚应重点防止第一次生理落果，尤力克柠檬和圆金柑应重点防止第二次生理落果。     

引进亚洲百合新品种的筛选

本研究以国外引进的11个亚洲百合品种为试验材料,通过箱式栽植将其种植在国家花卉工程中心温室内,并对植株生长高度、花蕾和花径大小等综合性状进行对比与分析,从中筛选出了适宜北京地区温室栽培的‘Black Out’、‘Cheops’和‘Navona’等3个百合切花品种以及名为‘Mount Duckling’的1个盆栽品种。本研究为亚洲百合新品种的筛选提供了一定的参考价值。     

水稻种植机械化发展现状及制约因素分析

水稻生产在我国粮食生产中占有非常重要的地位, 但由于其栽植环节生产技术复杂、季节性强、用工量多和劳动强度大等原因,生产效率比较低下,研究和加快推广机械化种植技术已成为当务之急.目前,我国水稻机械种植方式大体可分为机插秧、机直播和机浅栽(机抛秧或机摆秧)3大类,机插秧逐渐成为发展的主流.各种机械种植方式和机具推广中存在着多种不同的制约因素,影响了我国水稻种植机械化水平的快速提高.经过初步的调查与分析,认为区域性差异、农机与农艺的结合、机具的设计制造以及运行推广机制上存在着一些问题,需要采取有效措施予以解决.