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猪呼吸道病综合征(PRDC)是一种由多种细菌、病毒、支原体、环境应激以及因猪自身抵抗力降低等诸多因素相互作用引起的呼吸道疾病的总称。现代养猪业最困扰的问题就是呼吸道疾病,该病除导致猪直接死亡造成的损失外,还给养猪业带来饲料转换率低,生长缓慢,推迟上市以及管理上恶性循环等严重的经济损失。猪呼吸道疾病是许多因素综合作用的结果,这些因素包括社会、环境、饲养管理、应激、传染病源、饲料、药物等等,在诸多因素中管理因素起着重要的作用,改善管理和环境,许多呼吸道疾病即可减轻或得到控制。 相似文献
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Based on the diameter, height and biomass of different organs of Pseudosasa amabilis, an individual optimization model is established. The results showed that the relationships among diameter, height, and biomass of different organs followed the power function model, rather than exponential model, linear model, or polynomial model. The biomass proportion of large diameter grade increased apparently after culm harvesting, and diameter was mainly distributed from 4 to 5 cm diameter grade. The standing biomass of cultivated Pseudosasa amabilis was between 48.10 t·hm-2 and 53.10 t·hm-2, while standing biomass of non cultivated P. amabilis stand was between 66.90—70.40 t·hm-2, which is a suitable species for carbon sink. Bamboo individual biomass accounted for 70% of the above-ground biomass and grew multiply as the individual bamboo diameter increasing. The biomass of litter ranged from 8.32% to 18.10% in standing biomass while that of non cultivated bamboo stands was lower than that of cultivated bamboo. There existed a 1∶ 1 constant relationship between leaf biomass and branch biomass. 相似文献
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上海市闵行区以创建农产品质量安全区为抓手,通过建章立制、推广标准化生产、开展风险评估、提高认证比率、开展专项整治、加大宣传力度等措施,提升了闵行区农产品质量安全水平,但也发现存在基层监管力量不足、缺乏专业技术骨干、实验室硬件设施建设滞后、从事农业生产的人员年龄偏高、部分合作社负责人的农产品质量安全意识不高等问题,这些都制约了闵行区农产品质量安全工作的开展。为进一步确保闵行区农产品质量安全,要不断提高从业人员的法制意识、大力实施农业标准化生产、积极推动农产品质量安全可追溯体系建设。 相似文献
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