氮沉降对植物-丛枝菌根共生体影响的研究进展

氮沉降是影响陆地生态系统的重要环境因子。丛枝菌根真菌(AMF)作为一种能够与绝大多数植物共生并广泛存在的土壤微生物,对植物生长、养分吸收以及抗逆性等均具有重要的调节作用,而针对氮沉降对植物-丛枝菌根共生体影响的研究往往被忽视。基于此,笔者从氮沉降对菌根侵染特性、菌根多样性、菌根对宿主植物生长发育、氮代谢、磷吸收以及对宿主植物生物多样性影响等方面进行了归纳总结,并提出应重点关注的研究方向,旨为菌根生理生态学的研究提供一定的科学依据。     

放牧管理模式对高寒草甸生态系统有机碳、氮储量特征的影响

为探讨不同放牧管理模式高寒草甸生态系统有机碳、氮储量特征的变化,对青藏高原东缘禁牧(NG)、全生长季休牧(RG)、传统放牧(TG)和连续放牧(CG)4种放牧管理模式高寒草甸地上植被、地表凋落物、根系和土壤有机碳、氮储量进行测定和分析。结果表明,1)NG、RG和TG较CG显著提高了土壤、根系、植被和凋落物有机碳、氮储量。2)高寒草甸生态系统中,土壤有机碳储量所占比例最大(88.859%~98.242%),其次为根系(1.563%~8.742%),再次为植被(0.172%~1.430%),最小为凋落物(0.022%~0.969%);氮储量所占比例最大的是土壤(97.331%~99.633%),其次为根系(0.316%~2.071%),再次为植被(0.047%~0.442%),凋落物最小(0.003%~0.157%)。3)不同放牧管理模式土壤有机碳、氮储量具有明显的垂直分布特征,随土壤深度的增加土壤有机碳、氮储量明显降低。为期4年不同放牧模式仅对0~40 cm土层土壤有机碳、氮储量有影响。4)土壤有机碳、氮储量主要分布在0~40 cm土层,同时,放牧有使有机碳、氮向深层转移的趋势。5)NG、RG和TG显著提高了高寒草甸生态系统总有机碳、氮储量,而CG显著降低了总有机碳、氮储量,导致有机碳、氮的流失。禁牧和季节性休牧能有效增加青藏高原东缘高寒草甸生态系统有机碳、氮储量,实现碳、氮增汇的目的,是该区和类似区域草地放牧管理的重要模式。     

The use of antibiotics on small dairy farms in rural Peru

Very little is known about the use of antibiotics on small dairy farms in lower/middle-income countries. The use of these drugs can have profound impacts on animal health, farmer income and public health. A survey of 156 farmers was conducted in Cajamarca, a major dairy-producing center in the highlands of Peru characterized by small farms (<15 cows) to assess patterns and determinants of antibiotic use and farmers’ knowledge of antibiotics. The reported incidence of disease on these farms was relatively low (0.571 episodes of disease per cow-year), but more than 83% of the reported episodes were treated with antibiotics. The most commonly used antibiotics were oxytetracycline, penicillin and trimethoprim-sulfamethoxazole drugs; antiparasitic drugs were also used to treat what were likely bacterial infections. An increased incidence of treated disease was significantly associated with smaller farm size, lower farmer income, the previous use of the Californian Mastitis test on the farm and antibiotic knowledge. Farmers’ knowledge of antibiotics was assessed with a series of questions on antibiotics, resulting in a “knowledge score”. Increased knowledge was significantly associated with the use of antibiotics for preventative reasons, the purchase of antibiotics from feed-stores, the experience of complications in animals after having administered antibiotics, the number of workers on the farm and the educational level of the farmer. Overall, antibiotics appeared to be used infrequently, most likely because therapeutic interventions were sought only when the animal had reached an advanced stage of clinical disease. Few farmers were able to define an antibiotic, but many farmers understood that the use of antibiotics carried inherent risks to their animals and potentially to the consumers of dairy products from treated animals. The results of this study are useful for understanding the patterns of antibiotic use and associated management, demographic and knowledge factors of farmers on small dairy farms in rural Peru.     

Pattern and determinant of antibiotics used on broiler farms in Songkhla province,southern Thailand

The study was conducted on antibiotics use and determinant of use on 101 broiler farms in Songkhla province, Thailand. Ninety-six farms used the broiler production system under contracting companies and 5 farms were independently operated. All of the farms used antibiotics for disease prevention. Twenty agents in 9 classes of antibiotics were used; the most commonly used ones were enrofloxacin, amoxicillin, doxycycline, colistine and roxithromycin. There were 33 patterns of antibiotics use, the most frequently used being the combination of amoxicillin-enrofloxacin (21.18%). Cluster analysis suggested that the variation in antibiotic usage is mostly under the influence of the companies. Regulation of antibiotics use thus should focus on the company level.     

饲粮氮水平对牦牛瘤胃发酵及营养物质消化代谢特征的影响

本试验旨在探讨饲粮不同氮水平对牦牛瘤胃发酵及营养物质消化代谢特征的影响.试验选择4头体重相近[(148.5±9.2)kg]的3岁去势天祝白牦牛,采用4×4拉丁方设计,试验共分4期,每期21 d,4个饲粮氮水平[干物质(DM)基础]分别为低氮[粗蛋白质(CP)8.98%]、中低氮(CP 12.36%)、中高氮(CP 15...     

净、套作下大豆茎秆和籽粒糖氮动态规律研究

碳氮代谢是影响作物产量和品质的主要因素之一,在糖氮运输和储存过程中茎秆起着重要作用。以南豆12和南豆20为供试材料,在净、套作下分析不同生育时期大豆茎秆及籽粒中可溶性糖、氮含量变化规律,明确种植模式对大豆茎秆和籽粒碳氮的影响。结果表明,随着生育时期的推进,南豆12和南豆20茎秆可溶性糖和氮含量在净、套作条件下均呈现“低-高-低”的趋势,糖氮比呈现“低-高”的趋势。大豆从苗期至盛花期,茎秆可溶性糖、氮及糖氮比在净套作条件下差异显著(P<0.05),但从盛荚期至完熟期差异不显著(P>0.05)。净、套作模式下大豆籽粒可溶性糖、氮含量及糖氮比差异极显著(P<0.01),但品种间差异不显著。通过相关性分析,大豆盛花期到鼓粒期茎秆可溶性糖、氮含量及糖氮比与籽粒可溶性糖、氮含量及糖氮比相关性达到显著水平(P<0.05),特别是氮和糖氮比,相关系数最大值达到0.85。这些结果为明确糖氮由茎秆到籽粒的运输规律和套作大豆合理种植栽培参数提供理论支撑。     

罐装奶粉真空度形成影响因素研究

奶粉营养成分丰富,为避免罐装奶粉在货架期内出现胀罐情况,保证产品货架期的稳定性,一般采用气调包装并在罐内形成一定真空度。为研究罐装奶粉真空度影响因素,制备罐装奶粉并测试不同条件下罐内的真空度。通过对罐装奶粉进行长期跟踪测试,研究存储时间、存储温度、气体比例对罐内真空度形成的影响。结果表明,随着存储时间增加,罐内真空度呈现先快速增大后趋于平缓的趋势;在存储前期,37℃、47℃条件下的样品形成的真空度较常温更大;二氧化碳（CO2）的比例对罐内真空度形成的影响显著。     

高效饲料蛋白素代替部分棉仁粕对高温期奶牛产奶量的影响

高效饲料蛋白素由羟甲基尿素和微量元素组成。试验证明，在混合精料中添加１．５％高效饲料蛋白素、４％玉米、３．５％粉麸，以代替９％的棉仁饼，对牛奶产量没有不良的影响，且对因高温引起的产奶量自然下降有一定的稳定和缓冲作用。试验组下降幅度为６．７８％，而对照组为１０．４６％。     

低蛋白质饲粮补充过瘤胃赖氨酸和过瘤胃蛋氨酸对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响

本试验旨在研究低蛋白质饲粮补充过瘤胃赖氨酸(RPLys)和过瘤胃蛋氨酸(RPMet)对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响.选取36头健康无疾病的荷斯坦公牛,随机分为3组,每组12头牛.对照组(Ⅰ组)饲喂蛋白质水平为13％的正常饲粮,2个试验组(Ⅱ、Ⅲ组)均饲喂蛋白质水平为11％的低蛋白质饲粮,同时Ⅱ组补...