关于退牧还草的意义和技术标准问题探讨   总被引：20，自引：4，他引：16  

杨汝荣 《草业科学》2004,21(2):41-44

退牧还草是一项长期而又复杂的系统工程,需要统筹考虑、科学规划、合理安排.但各地在实际操作中对究竟怎么退、如何退,缺乏规范和技术标准,这集中表现在没有明确什么样的草地需要禁牧、什么样的草地需要休牧、什么样的草地需要轮牧等问题上.禁牧、休牧和轮牧的工程标准和技术措施缺乏,给当前正在进行的退牧还草工作带来很多混乱和困难.因此,规范退牧还草的技术标准是当前退牧还草工作首先要解决的问题.  相似文献   

不同模式下农村宅基地退出的风险评价及防范对策研究——以福建省晋江市为例   总被引：1，自引：1，他引：0  

梁发超  林彩云 《农业现代化研究》2019,40(6):1011-1020

开展不同模式下农村宅基地退出的风险评价及其防范对策研究是合理引导农户退出宅基地的前提条件。基于农户的微观福利视角,构建宅基地退出后的风险识别指标体系,利用福建省晋江市的调研数据,运用层次分析法和模糊综合评价法,对不同模式下宅基地退出的风险进行综合评价,探讨并提出对应的防范对策。结果表明：晋江市农村宅基地退出主要有指标置换和资产置换两种模式。总体来看,两种宅基地退出模式的综合风险分值均处于中警级别,两种模式对农户宅基地退出都具有比较较大的影响。政策了解程度在两种模式中均处于重警级别,农户的知情权没有得到切实保障;家庭日常支出和人均居住面积在资产置换模式下处于重警级别。研究表明,不同模式下宅基地退出的基本动机和政策安排存在差异,使其对农户产生的影响有所不同。因此,在宅基地退出过程中应科学设定补偿标准和范围、规范宅基地退出程序和采取差别化的方式来推动农户参与,进而为农户退出宅基地提供针对性的风险防范对策。  相似文献   

Kinetic analysis of oxytetracycline residues in Chinese mitten crab,Eriocheir sinensis,muscle following intramuscular administration     

Q Feng  T Gao  H Ji  X Jiang  T Liang  W Gu  G Wu  G Gao  W Wang 《Journal of fish diseases》2010,33(8):639-647

Crab culture is a very important economic industry in China. An epidemic of tremor disease of Chinese mitten crabs, Eriocheir sinensis, has become a serious problem in recent years. A spiroplasm has been proved to be the causative agent of this disease. Oxytetracycline (OTC) is used widely in aquaculture and was confirmed to be very effective against this pathogen. In this study, the distribution and depletion patterns of OTC in crab muscle were evaluated following single intramuscular doses of 2, 8 and 40 mg kg^?1 body weight. OTC was detected with a validated HPLC method. Concentration–time profiles were well described by a three‐compartment model with first‐order absorption after a single dose of 8 and 40 mg kg^?1. For comparison, a non‐compartment model was employed. A withdrawal time of 48.29 and 55.92 days was suggested prior to consumption after receiving 8 and 40 mg kg^?1. A recommended therapeutic dose of OTC in theory was calculated to be 36.37 mg kg^?1. OTC was distributed well throughout the body. The elimination of OTC in muscle was slower compared with fish and other crustaceans. A dose of 40 mg kg^?1 is suggested for practical use.  相似文献   

问题金融机构市场退出的基本范畴分析     

黎四奇 《湖南农业大学学报(自然科学版)》2013,(6):111-115

市场主体的进退是市场得以循环与净化及保证活力的必然要求。如果不能从范畴的角度廓清市场退出的本位，则也难以摆正金融机构市场退出法律制度所应包括的内容，从而出现问题救助与市场退出纠缠不清的局面。在后危机时代，从金融机构市场退出的界定、价值取向及利益博弈的角度阐明所涉问题的基本范畴对于理念创新及制度完善的意义是不言而喻的。  相似文献   

功能价值视角下农民宅基地自愿有偿退出补偿标准测算方法   总被引：2，自引：0，他引：2  

刘丹  巩前文 《中国农业大学学报》2020,25(12):173-183

为探讨农民宅基地自愿有偿退出补偿标准的测算方法，采用宅基地功能价值理论，从宅基地4大功能维度构建农民宅基地自愿有偿退出补偿价值体系，建立农民宅基地自愿有偿退出补偿标准测算模型，并以全国10 省20 个村庄1 242 个农户的问卷调研数据为依据，实证分析不同类型村庄农民对宅基地功能需求的差异，将宅基地功能需求率作为修正系数引入宅基地退出补偿标准测算模型，实证测算集聚提升类村庄江苏省镇江市句容市后白镇西冯村农民宅基地自愿有偿退出补偿标准。研究发现:1)宅基地住房保障功能、生产经营功能、经济财产功能和情感传承功能的经济效用是宅基地退出补偿价值体系的重要内容；2)宅基地的住房保障价值可通过城镇居民低收入家庭廉租房补贴测算，宅基地生产经营价值可通过农户从事分散式畜禽养殖收益测算，宅基地经济财产价值可通过宅基地用途转变收益测算，情感传承价值可通过农村人均文化娱乐支出测算；3)依据功能价值论测算的农民宅基地自愿有偿退出补偿标准高于实践中农民宅基地自愿有偿退出补偿标准。因此，国家需依据功能价值论制定农民宅基地自愿有偿退出补偿指导意见，以不同类型村庄农民宅基地功能需求差异为基础，制定差异化的农民宅基地自愿有偿退出方案。  相似文献   

盐酸沙拉沙星在凡纳滨对虾体内的残留消除规律     

李国烈  胡琳琳  胡伟国  房文红  孙贝贝  黄伟  周帅 《华中农业大学学报》2012,31(5):650-655

在水温为(29.0±1.0)℃、盐度为3.3%条件下,以30mg/kg的剂量单次药饵投喂凡纳滨对虾盐酸沙拉沙星后,分别取凡纳滨对虾血淋巴、肝胰腺和肌肉样品,采用反相高效液相色谱法测定样品中的药物浓度。结果表明:盐酸沙拉沙星在肝胰腺中的药物残留浓度远高于血淋巴和肌肉,后两者的药物残留浓度比较低而且血淋巴中的残留浓度高于肌肉;给药后盐酸沙拉沙星在血淋巴、肝胰腺和肌肉中的消除速率快慢不一,在肌肉中消除速度最快,肝胰腺中的消除速度快于血淋巴。  相似文献   

兴安落叶松规格材齿板连接节点的拉伸性能     

席佳  赵荣军  费本华  叶虹  王朝晖 《木材工业》2009,23(5)

采用国产落叶松规格材及进口齿板连接件构造节点,依据国标对齿板接合节点的延性比、齿极限承载力、齿板极限受拉承载力及设计值进行评估。结果表明,采用Foschi公式对试验曲线进行拟合,结果良好;齿板节点的延性比随节点构造方式的不同而异,顺纹节点的延性比均大于2.0,明显高于横纹节点,符合抗震结构的要求。  相似文献   

单季不施氮肥对太仓水稻土的微生物功能多样性的影响   总被引：3，自引：0，他引：3  

张华勇  林先贵  李忠佩  尹睿  褚海燕  车玉萍  杨林章 《土壤》2005,37(6):655-658

氮肥的过量施用在浪费资源的同时也污染了环境,单季不施N肥是太仓地区探索的减少N肥施用量方法中的一种。本文通过比较短时期的单季不施N肥区和常规施肥区中土壤中微生物的数量和群落水平的功能多样性指数来研究单季不施N肥对土壤质量的影响。结果表明:细菌、真菌、放线菌的数量在两种施肥方式下没有显著差异;BIOLOG平板法获得的平均吸光度、多样性指数Shannon指数H’和Simpson指数的变型G在两种施肥方式下没有显著差异;主成分分析(PCA)在95种因子中提取的3个主成分因子,尽管主成分因子2在两种施肥方式下略有差别,主成分因子1和3却无法区分两种施肥方式。这说明短时期的单季不施N肥不会对土壤中微生物数量造成影响,对土壤微生物功能多样性也仅对细微有影响。  相似文献   

Effects of temporary cessation of milking following intramammary cefazolin sodium infusion on residual antibiotic in lactating dairy cows     

Kaoru SATO  Eiichi OHASHI  Kenji TSUKANO  Keiko IKEDA  Tadaharu AJITO  Kazuyuki SUZUKI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2021,83(5):814

The aims of studies were to estimate the withdrawal period of antibiotic from milk after the intramammary infusion of cefazolin sodium (CEZ) in cows with difficulties in frequent milk discharge due to disease such as teat injury. The period was compared among cows milked twice a day after 150 or 450 mg of CEZ were administered to all quarters (Study 1, 2) and the cows in which milking of front-right quarter was ceased for five days after administration of these infusions to only that quarter (Study 3). In Studies 1 and 2, the median of 17.66 µg/ml and 83.18 µg/ml of CEZ were detected in the samples of first milking after intramammary administration, respectively; however, there was no residual antibiotic by 72 hr in all cows. In Study 3, the median of 1.96 µg/ml of CEZ was detected in the sample after the resumption of milking at 120 hr, and the residual was eliminated by 174 hr. The withdrawal period may be prolonged by the cessation of milking after administration, and the period is the total time from cessation to 72 hr after the resumption of milking.  相似文献   

Farming practices in Sweden related to feeding milk and colostrum from cows treated with antimicrobials to dairy calves     

Anna Duse  Karin Persson Waller  Ulf Emanuelson  Helle Ericsson Unnerstad  Ylva Persson  Bj?rn Bengtsson 《Acta veterinaria Scandinavica》2013,55(1):49

Background

Milk produced by cows in receipt of antimicrobial therapy may contain antimicrobial residues. Such antimicrobial-containing waste milk must be withdrawn from human consumption and is therefore sometimes used as calf feed. Unfortunately, this approach might promote selection of antimicrobial resistant bacteria in the calves’ intestinal microbiota. The objectives of this study were therefore to obtain an overview of waste milk feeding practices on Swedish dairy farms and to investigate if these practices were associated with certain farm characteristics. A representative group of 457 Swedish dairy farmers participated in a web-based survey with questions about the use of colostrum and milk from cows treated with antimicrobials at dry off or during lactation, respectively, as calf feed.

Results

Colostrum (milk from the first milking after calving) and transition milk (milk from the second milking to the fourth day after calving) from cows treated with antimicrobials at dry off was fed to calves on 89% and 85% of the farms in the study, respectively. When antimicrobial therapy was given to cows during lactation, 56% of the farms fed milk that was produced during the course of treatment to calves, whereas milk that was produced during the subsequent withdrawal period was fed to calves on 79% of the farms. Surveyed farmers were less prone to feed such milk if the antimicrobial therapy was due to mastitis than other infections. In Sweden, a majority of antimicrobial treatments during lactation are systemic administration of benzylpenicillin and thus, the bulk of waste milk in Sweden is likely to contain residues of this drug. Feeding waste milk to calves was more common on non-organic farms, and on farms located in Southern Sweden, and was less common on farms with cows housed in cold free stalls barns.

Conclusions

Waste milk that may contain antimicrobial residues is, at least occasionally, used as feed for calves on a majority of surveyed Swedish dairy farms. Future work should focus on the effect of waste milk feeding on the occurrence of antimicrobial resistant bacteria in the calves’ intestinal microbiota.  相似文献