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The biological cleaning agent Pondplus was dowsed each ten days at different dosage into breeding ponds for Chinese mitten crab with stocking rate at 12 000 ind./ha, to evaluate its purification effects on water environment in breeding ponds and its effects on Chinese mitten crab growth. The results showed that dousing treatment improved the water quality significantly as evaluated according to the parameters of DO, CODMn, NH4 ＋ - N and NO2 - -N. Particularly, when the air temperature was higher than 35℃, the diurnal observation on DO values at the bottom of ponds showed that dousing at 450 g/（ ha•m） gave a DO value higher than 4 mg/L all day long, which was 2 mg/L higher than that of control. The observed increase of Chinese mitten crab were 14. 9% , 27.8% , 27.8% by average weight, when dousing at 150, 300, 450 g/（ha • m） , respectively. Accordingly, the production increased by 8.5%, 11.9%, 18.6% through its promotion of Chinese mitten crab growth, and the economic efficiency were enhanced by 96.2% , 159.8% , 180.9%. 相似文献
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绵羊球虫在内蒙较为常见,通常造成羔羊发育受阻、生产性能下降,偶尔引发死亡。为了摸清呼伦贝尔草原绵羊球虫的种类,我们于1998～2000年对来自呼伦贝尔草原主体部分牧业四旗的150只绵羊进行了球虫检查,旨在为进一步制定防治对策、减少不必要的损失,促进养羊业更快发展提供科学依据。1 材料和方法粪便采自海拉尔区南门外屠宰场,选来自牧业四旗的当年羔羊(其中:新左旗40只、新右旗30只、陈旗40只、鄂温克旗40只)做为检查对象,宰前肛门取粪。用离心漂浮法收集卵囊,从每份粪样取10g置于烧杯内,加饱和盐水捣碎,过60和200目筛,滤液2000r/min… 相似文献
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