不同粗蛋白水平日粮对种公鸡繁殖性能的影响

试验以21周龄新扬州种公鸡为对象,研究了不同粗蛋白水平日粮对种公鸡繁殖性能的影响。结果表明,粗蛋白质水平为14%的B组公鸡精液量、精子活力和精子密度均明显地高于粗蛋白水平为11%的A组和粗蛋白质水平为17%的C组,而精子畸形率为B组最低(P>0.05);日粮粗蛋白水平对成年种公鸡的睾丸性状影响不大(P>0.05),而年龄对公鸡的睾丸性状有着显著的差异(P<0.05);A组的血浆中睾酮T、促黄体素LH和促卵泡素FSH含量分别比B组高了6.34%、19.64%和3.88%,比C组高了7.20%、17.54%和9.84%,差异不显著(P>0.05)。     

立式导叶自吸泵内部湍流的大涡模拟

采用大涡模拟方法,运用CFD软件CFX对设计工况下的立式导叶自吸泵内部三维不可压缩湍流流场进行数值模拟。得到了其内部流场的压力分布和速度分布情况,对立式导叶自吸泵内部流场的相对速度分布和压力分布进行分析,对模型泵进行性能预测,得到了性能预测曲线,并进行了性能试验,结合预测结果与试验结果进行对比,说明大涡模拟法能够较准确地预测立式导叶自吸泵性能和内部流动特性,为立式导叶自吸泵的设计研究提供参考。     

泡桐叶片总DNA甲基化水平测定方法

采用高效液相色仪,色谱柱为Thermo Hypersil C18BDS,以pH4.0的甲醇-戊烷磺酸钠10mmol/L-三乙胺(10-90-0.2,v/v)为流动相,流速0.5mL/min,柱温30℃,在Waters2487紫外-可见分光光度检测器273nm处,测定泡桐叶片DNA水解样中胞嘧啶和5-甲基胞嘧啶的含量,泡桐叶片DNA总甲基化水平用5-甲基胞嘧啶占DNA样品中总胞嘧啶碱基的百分数表示。     

中国小熊猫生态学研究现状

概述了中国小熊猫的分布现状、栖息地状况,进一步阐明了目前对我国小熊猫的研究主要集中在生境和食物选择方面,且研究地区主要在四川进行,分析了我国小熊猫保护面临的受到人类活动的干扰、森林过度采伐、乱捕滥猎等问题,提出了加大投入、扩大保护面积、建立和实施保护补偿制度、提高公众保护意识以及加强科学研究等相应的保护对策。     

毛竹低产低效林的经营策略研究

毛竹是南方竹产区山区农户主要经济收入来源和当地农业经济的支柱产业之一.当前,毛竹低产低效林面积依然很大,占竹林总面积的60％左右.该文以农户访谈和二手资料收集等方法,了解掌握毛竹低产低效林改造的技术状况和运行机制,从毛竹培育技术、农户对技术采用和扩散的特征分析出发,提出了毛竹低产低效林的经营策略建议.     

Is it economically feasible to harvest by management zone?

The economics of harvesting wheat based on input management zones in the northern wheatbelt of Western Australia was studied using a simulated field of regular dimensions with varying zone sizes and layouts. Fertilizer application rates and crop yield and quality data from field trials of input management were used to estimate the gross crop revenue and harvesting costs from the different field layouts and zone combinations. As a general observation there was no consistency in the results; harvesting by zone generated more gross income in some combinations of field layout and yield quantity scenarios, but not in others. However, there were key factors in determining whether it was profitable to harvest by zone. These were prior knowledge of the potential yield and quality characteristics of grain from each zone in a field, and the layout of zones within a field.     

复合酸化剂对断奶仔猪生产性能的影响

为研究复合酸化剂对断奶仔猪生产性能的影响,此次试验选取了40头28±2日龄杜×长×大三元杂交断奶仔猪,并将它们随机分成4个处理组。这4个处理组均饲喂基础日粮,其中,试验1、2、3组分别添加0.1%复合酸化剂、0.2%复合酸化剂、0.3%复合酸化剂,对照组不做任何处理。试验结果表明,在30d试验期内,试验组仔猪比对照组仔猪平均日增重分别提高了5.9%、13%、10.24%,其中基础日粮中添加0.2%复合添加剂的试验组与对照组日增重差异显著(P<0.05);料肉比分别下降了7%、10.21%、8.13%;并且试验组的仔猪腹泻率较之对照组有明显的下降。试验发现,日粮中添加复合酸化剂能显著改善断奶仔猪生产性能,复合酸化剂添加量为0.2%时,仔猪的生产性能最佳。     

肉兔不同杂交组合的生产性能试验报告

选择适合本地的3个优良品种及6个杂交组合,探讨不同组合的产仔数、初生窝重、30日龄断奶窝重、30日龄断奶成活率、90日龄成活率、90日龄个体重等生产指标,筛选最优杂交组合。结果表明:肉兔不同品种杂交生产性能明显提高;最优杂交组合为大♀×加♂杂交组合和加♀×新♂杂交组合;6个杂交组合90日龄个体重平均增加109g。     

黑龙江林区平菇栽培管理与病虫害防治技术

介绍了适合黑龙江林区培育的平菇主要栽培品种,从林分选择、菌种选择、作床播种、管理、病虫害防治等方面提出具体经营管理办法。     

An empirical bio-economic stocking model for floodplain beels in Bangladesh

While stocking floodplain depressions or beels with fingerlings is a common form of fisheries management in Bangladesh, bio‐economic guidance for improving the outcome of stocking strategies is sparse. The Community‐Based Fisheries Management (CBFM) Project, funded by the Ford Foundation and the UK Government's Department for International Development (DfID) promoted stocking practices in beels throughout the country as a means to improve fisher livelihoods. This paper describes an empirical bio‐economic model developed using data generated under the CBFM project. The model offers guidance on selecting stocking densities depending upon the available size (length) of fingerlings to maximize profit and return on investment while minimizing risk. Because large fingerlings are relatively inexpensive and have lower rates of natural mortality, the model predicts that it is more profitable to stock large fingerlings at low densities than small fingerlings at high densities. These general recommendations were found to be largely insensitive to the market price for harvested fish. To minimize credit burden and financial risk, minimum stocking densities should be selected according to the length of fish available that maximizes profit. Because of its empirical nature, the model recommendations may not be applicable beyond the project sites. Furthermore, it is recommended that attempts be made to field test the model predictions before widespread adoption or promotion.