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61.
以张家港农田土壤作为研究对象,在实验室测定土壤重金属元素As、Cd、Cr、Cu、Zn、Ni、Pb、Hg的含量,并与土壤可见近红外高光谱数据建立土壤重金属含量的定量估测模型,以快速获取研究区农田的土壤重金属含量。为保证模型预测的精度和稳定性,首先,对原始高光谱数据进行平滑处理,并进行一阶导数、倒数一阶导数、倒数的对数一阶导数、平方根一阶导数和连续统去除等形式的光谱变换;然后,提取不同变换光谱的特征波段进行相关性分析;最后,通过逐步回归法建立重金属含量的定量估算模型。结果表明:张家港市农田土壤中Cd、Hg、Cu、Zn存在一定的污染风险。在高光谱的不同变换形式中,一阶导数和连续统去除与重金属含量的相关系数高于其他变换形式。基于8种土壤重金属含量与高光谱数据建立的定量估算模型具有良好的预测精度。Cd、Hg、Cr、As、Cu、Zn、Ni、Pb估算模型的实际值与验证值的拟合度分别为0.874、0.879、0.800、0.646、0.513、0.655、0.603和0.542,可用于预测张家港市的农田土壤重金属含量。 相似文献
62.
Jian‐Jun Wu Wei Liu Ming Jiang Ying Zhou Wei‐Min Wang Hua Wen Hong Liu 《Aquaculture Nutrition》2020,26(5):1822-1834
This study investigated the effects of dietary exogenous protease on the growth performance, intestinal health, immune parameters and disease resistance of genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Five test diets with commercial protease at the levels of 0, 1.38, 2.76, 5.52 and 11.04 U/g (named PE0, PE1, PE2, PE5 and PE11, respectively) were administered to triplicate tanks with 30 fish for 60 days, and then, the fish were challenged with Streptococcus agalactiae for 14 days. The results indicated that weight gain increased as exogenous protease increased from 0 to 5.52 U protease/g diet and then decreased significantly (p < .05) with a further increase in exogenous protease supplementation (p < .05). The height of the villi in the proximal intestine and distal intestine, the width of the villi in three segments of the intestine, and the thickness of the muscle layer in the proximal intestine and mid‐intestine (p < .05) were increased in the fish fed the PE5 diet. Immune and antioxidant indices (except malondialdehyde), and survival after challenged with S. agalactiae were higher in fish fed PE5 diets than in those fed other diets (p < .05). In conclusion, 5.52 U/g protease supplementation in a plant‐based diet could promote the growth performance, intestinal physical barrier function, innate immunity and S. agalactiae resistance of GIFT. 相似文献
63.
Seyyed Morteza Hoseini Ali Taheri Mirghaed Melika Ghelichpour 《Aquaculture Research》2020,51(4):1455-1463
Rainbow trout (Oncorhynchus mykiss) was reared under low (LD) and high (HD) stocking densities for 70 days, during which they were fed with diets supplemented with 0, 5 and 10 g tryptophan (Trp) per kg. At the end of the experiment, there were significant interaction effects of the stocking density and Trp levels on plasma Trp, globulin, lysozyme, catalase (CAT), malondialdehyde (MDA), and bactericidal activity and blood leucocyte count. However, there was no difference in plasma complement (ACH50), total immunoglobulin (Ig), total antioxidant capacity (TAC), superoxide dismutase (SOD) and blood differential leucocyte count. Trp at 5 g per kg diet significantly increased lysozyme and bactericidal activity, and decreased MDA under both the LD and HD conditions. Moreover, it significantly increased plasma CAT and blood leucocyte under the LD and HD conditions respectively. Trp at 10 g per kg diet significantly increased blood leucocyte and plasma bactericidal activity under the LD condition, but significantly decreased plasma globulin and bactericidal activity under the HD condition. In conclusion, the present results showed that the effects of Trp on immune and antioxidant systems depend on Trp levels and stressful conditions. As 5 g Trp per kg diet is beneficial for rainbow trout well‐being under both the LD and HD conditions, higher level of Trp (10 g/kg) is not beneficial and even causes some negative effects under the HD condition. 相似文献
64.
SS Greening K Mulqueen TG Rawdon NP French MC Gates 《New Zealand veterinary journal》2020,68(5):261-271
ABSTRACT Aims: To collect baseline data on the contact risk pathways and biosecurity practices of commercial poultry farms in New Zealand, investigate the relationship between the farm-level disease contact risks and biosecurity practices, and identify important poultry health concerns of producers. Methods: A cross-sectional survey of all registered New Zealand commercial poultry operations was conducted in 2016 collecting information on farm demographics, biosecurity practices, and contact risk pathways. Survey responses were used to generate an unweighted subjective disease risk score based on eight risk criteria and a subjective biosecurity score based on the frequency with which producers reported implementing seven biosecurity measures. Producer opinions towards poultry health issues were also determined. Results: Responses to the survey response were obtained from 120/414 (29.0%) producers, including 57/157 (36.3%) broiler, 33/169 (19.5%) layer, 24/55 (44%) breeder, and 6/32 (19%) other poultry production types. Median disease risk scores differed between production types (p?<?0.001) and were lowest for breeder enterprises. The greatest risk for layer and broiler enterprises was from the potential movement of employees between sheds, and for breeder enterprises was the on- and off-farm movement of goods and services. Median biosecurity scores also differed between production types (p?<?0.001), and were highest for breeder and broiler enterprises. Across all sectors there was no statistical correlation between biosecurity scores and disease risk scores. Producers showed a high level of concern over effectively managing biosecurity measures. Conclusions: The uptake of biosecurity measures in the commercial poultry farms surveyed was highly variable, with some having very low scores despite significant potential disease contact risks. This may be related to the low prevalence or absence of many important infectious poultry diseases in New Zealand leading farmers to believe there is a limited need to maintain good biosecurity as well as farmer uncertainty around the efficacy of different biosecurity measures. Further research is needed to understand barriers towards biosecurity adoption including evaluating the cost-effectiveness of biosecurity interventions. 相似文献
65.
为实时掌握水产养殖水质和气象环境信息,针对溶氧控制过程中非线性、惯性大和时滞的问题,以循环水流水槽养殖模式为基础,设计了水产养殖环境监测和控制系统。通过PLC对养殖环境中溶氧、pH、温度、湿度、风速、风向、大气压等参数进行信息采集与传输,上位机实时显示环境信息,用模糊算法处理信息,处理后的结果作为PLC的输出传送到变频器中,变频器控制增氧机调节水中溶氧量。结果显示:该系统可实时传输与显示上述参数信息,提供历史数据和环境异常报警功能。模糊控制在调节溶氧过程中超调小、精度高,溶氧偏差±0.4 mg/L,可减少增氧机启停次数、延长设备寿命。监控系统进行实地应用测试,达到预期效果,可在水产养殖中进行推广和应用。 相似文献
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