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1. An experiment was conducted to investigate the possibility of lowering the yolk cholesterol of the egg by supplementing the diet with supraoptimal amounts of copper (50, 150 or 250 mg/kg) as sulphate or acetate. 2. A significant reduction in egg production and a negative effect on food conversion was found when 250 mg/kg of copper was added compared to the control (no added copper). Acetate seemed significantly less harmful in both cases. 3. A significant linear reduction was found in plasma and yolk cholesterol (20% and 14%) and in plasma and yolk triglycerides (24% and 30%) as the dietary copper content was increased from 0 to 250 mg/kg. 4. Regardless of type or quantity of copper, cholesterol and lipids were decreased linearly as birds remained longer on the treatments. A significant interaction between quantity and period showed a greater reduction at a later time. 5. If slightly lower egg production can be accepted, the addition of 250 mg/kg copper might be beneficial in reducing the cholesterol content of the yolk. 相似文献
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华南亚热带作物科学研究所粤西試験站 《土壤学报》1966,14(1):13-21
我国热带地区具有高温多雨、雨量分布不均匀且多暴雨的特点,容易引起水土流失,土壤有机质分解快,养分淋溶流失强烈,因此热带地区的红壤和砖红壤的有机质和速效养分含量都很低。热带经济林木和果园间种绿肥覆盖作物可以保持水土,增进地力,促使主作物速生高产[1,2],而建立牧草基地以发展畜牧业和种植绿肥是增加优质有机肥料来源的有效途径。这样才有可能增施大量有机肥料,不断提高土壤肥力,保证农林作物稳产高产。 相似文献
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Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area,Jordan,where intensive greenhouse production system（IGPS） has been practiced since 1998,to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system.The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil（control）.Quality and amount of irrigation water,lack of efficient drainage,and quantity and types of applied fertilizers were major factors resulting in salt buildup.IGPS resulted in lower total N（TN） and NO3-N in the soil compared to the control.The lower TN was due to crop uptake,microbial immobilization,volatilization,and irregular application of composted animal manure or poultry manure.In contrast,higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control.Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers.Residual available K in the soils of greenhouses was relatively lower than that in the control and it was,however,classified as high to very high.A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment.Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production.This can be accomplished through education,targeted towards the farming community in the central Jordan Valley. 相似文献
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Bedrock landsliding is a dominant geomorphic process in a number of high-relief landscapes, yet is neglected in landscape evolution models. A physical model of sliding in beans is presented, in which incremental lowering of one wall simulates baselevel fall and generates slides. Frequent small slides produce irregular hillslopes, on which steep toes and head scarps persist until being cleared by infrequent large slides. These steep segments are observed on hillslopes in high-relief landscapes and have been interpreted as evidence for increases in tectonic or climatic process rates. In certain cases, they may instead reflect normal hillslope evolution by landsliding. 相似文献
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J. M. AL‐Awadhi 《Land Degradation \u0026amp; Development》2013,24(1):2-11
Soil degradation and vegetation deterioration in contrasting areas (open desert versus protected desert) in the northeastern part of Kuwait were investigated, using field measurements, and laboratory methodologies. The average infiltration rate of compacted soils studied was found to be 52 per cent lower than that of the undisturbed soils we investigated. The bulk density of the compacted soils was 19 per cent higher than that of the non‐compacted soils. The average topsoil resistance of severely compacted soils was 13 per cent greater than that of undisturbed soils and is mainly due to overgrazing, and off‐road vehicle use. We found that the overall vegetation cover status of open areas investigated was approximately 70 per cent less than for the protected areas studied. As a consequence of soil compaction and vegetation deterioration, sand deflation processes, and sand movement prevail in open areas. The total average percentages of course grain sizes in unprotected soils and heavily disturbed soils by vehicles (off‐road) are 51 and 103 per cent greater, respectively. The annual rate of sand transport during the last 20 years, from the prevailing wind direction (NW) in the area has increased by 81 per cent. The delicate balance between soil and natural vegetation cover is easily disturbed by off‐road vehicle use associated with overgrazing and recreation activity. A restoration plan is needed in order to reduce land degradation and to allow natural vegetation recovery. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献