Effect of ammonia and nitrite on vigour,survival rate,moulting rate of the blue swimming crab <Emphasis Type=Italic>Portunus pelagicus</Emphasis> zoea

The effects of ammonia and nitrite on vigour, survival rate, moulting rate of zoea of blue swimming crab, Portunus pelagicus, were studied. A total of five nitrite-N treatments (26.67, 53.34, 106.68, 213.36, 426.72 mg/l) and a control (no nitrite-N added) were set up for the acute nitrite-N toxicity experiment; a total of five ammonia-N treatments (8.43, 16.86, 33.72, 67.44, 134.88 mg/l) and a control (no ammonia-N added) were set up for the acute ammonia-N toxicity experiment. The results showed that the vigour, survival rate and moulting rate of zoea of the blue swimming crabs exposed to over 53.34 mg/l were significantly different (P < 0.05) from the control group. The zoea LC₅₀ values (mg/l) of nitrite-N were 179.47, 76.56, 66.70, 37.49, 25.01, 25.35, 25.34 mg/l for 24, 36, 48, 60, 72, 84, 96 h, respectively. The vigour, survival rate and moulting rate of zoea of the blue swimming crabs exposed to over 16.86 mg/l were significantly different (P < 0.05) from the control group. The zoea LC₅₀ values (mg/l) of ammonia-N were 51.04, 39.62, 38.72, 24.43, 16.90, 13.42, 11.16 mg/l for 24, 36, 48, 60, 72, 84, 96 h, respectively. The zoeae are highly sensitive to ammonia and nitrite, and the toxicity of ammonia and nitrite on Portunus pelagicus decrease with development of this crab.     

“六五”至“十二五”期间我国棉花品种纤维品质评价分析

对"六五"至"十二五"期间国家棉花区域试验参试品种纤维品质进行了总结和分析,结果表明,我国棉花品种的综合纤维品质总体趋势是稳步改良,逐年提升。黄河流域棉区品种的纤维长度和断裂比强度呈优化发展趋势;长江流域棉区品种纤维长度、断裂比强度和纺纱均匀性指数呈优化发展趋势;西北内陆棉区品种纤维品质总体表现有上升趋势,但近5年来纤维品质表现略有下降趋势。     

无人机低空数字图像诊断棉花苗情技术

为了提高棉花苗情监测的时效性和精确性,本研究利用无人机低空获取棉田数字图像,通过图像分析快速识别诊断棉花苗情。研究结果表明,利用HIS（Hue- intensity- saturation）阈值法将图像二值化,之后通过腐蚀膨胀对二值化图像进行处理,能够较好地排除地膜干扰,快速识别大范围棉苗数量和壮苗数量,棉苗识别精度超过90%。基于图像识别结果绘制的田间苗情分布图清晰显示了棉田出苗情况,并为精准化管理提供依据。本研究结果可为无人机在农业中的应用提供参考。     

Cryopreservation of trochophore larvae from the hard clam Mercenaria mercenaria: Evaluation of the cryoprotectant toxicity,cooling rate and thawing temperature

Aquaculture of hard clams Mercenaria mercenaria is a $65 million industry along the east coast and Gulf of Mexico coast in the United States. The goal of this study was to develop a preliminary protocol to cryopreserve trochophore larvae of hard clams. The objectives were to evaluate the: 1) toxicity of cryoprotectants, including dimethyl sulfoxide (DMSO), propylene glycol, ethylene glycol and glycerol, at 5, 10, 15 and 20% for exposure time of 1, 15, 30, 45, 60 and 75 min; 2) effects of cooling rates (5, 10, 20 and 30°C/min for the first trial; and 1, 3 and 5°C/min for second trial from 4 to ?80°C), thawing temperature (30, 40 and 50°C) and their interactions on post‐thaw viability. A basic protocol was concluded as: 15‐hr trochophore larvae mixed with DMSO or propylene glycol (5, 10%), equilibrated for 15 min, cooled in a programmable freezer from 4 to ?80°C at a cooling rate of 5°C/min and thawed at 50°C for 6 s. With this protocol, the immediate post‐thaw trochophore survival was 23 ± 14%, and survival to D‐stage was 27 ± 14%. This is the first report on larval cryopreservation in the hard clam and would have application for genetic breeding and seed production.     

柑桔配施氮、磷、钾肥效应研究初报

本试验研究了在同一施氮水平下，不同水平磷、钾配施及施用不同种类钾肥对柑桔营养、产量及品质的效应。结果表明，紫色黄泥土锦橙园采用适当氮、磷、钾肥配合施用对提高单产及改善果实品质具有明显作用，以株施Ｎ４６０９、Ｐ_２Ｏ_４００ｇ、Ｋ_Ｏ５６０ｇ效果最佳，经济效益也最大。在一定范围内，叶片中的磷、钾养分含量都随磷、钾化肥用量的增加而提高。     

Prevalence of Giardia spp. infection in pre-weaned and weaned calves in relation to management factors

Two hundred and forty calf faecal samples from 16 Malaysian farms were screened by PCR for Giardia spp. The overall prevalence was 12.5% and the overall farm prevalence was 68.8% (11/16 farms). The prevalence in pre-weaned and weaned calves was 16.7% and 8.3%, respectively. Sequence analysis of 25 isolates identified all as G. duodenalis assemblage E. Management factors associated with an increased risk of infection with Giardia spp. included keeping weaned calves in pens with sand floors and calf age. Keeping pre-weaned calves in pens with concrete floors and calving in single cow calving areas decreased the risk.     

对虾养殖中新生残饵耗氧动态及其规律的研究

本文根据实验模拟研究的结果，估算了由配合饵料和贻贝肉形成残饵后３６天时间内的耗氧量，并讨论了其耗氧动态和规律。残饵耗氧量的变化范围为４．０９～１７．６１ｇ／ｋｇ·ｄ。残饵耗氧曲线随残饵形成时间的不同而显著变化，且始终呈二次曲线衰减形式，在其演变过程中，该二次曲线方程的二次项系数由负数逐渐演变为正数，并最终接近于污染虾塘底质的耗氧曲线。配合饵料和贻贝肉的耗氧曲线变化形式相近，但程度上存在较大差异。另外，本文还初步探讨了残饵的耗氧高峰期，估算了残饵在虾塘底质总耗氧量中的作用。     

病原菌诱导黄瓜对其主要病害的抗病反应

以5种黄瓜主要病原菌作为诱导抗病因子,研究其对黄瓜主要病害的作用,结果发现黄瓜经病原菌诱导后,可以产生对诱导病原菌及其它病原菌引起病害的交互保护作用,并且诱导的交互保护作用与诱导浓度、诱导间隔期、不同品种存在相关性.诱导效果不随诱导接种浓度的升高而升高.在黑星病菌对霜霉病菌的诱导作用中,以浓度为1×102个/ml的黑星病菌孢子悬浮液的诱导效果最好,诱导间隔期为48h黄瓜黑星病菌对霜霉病的交互保护作用最明显,抗性品种的交互保护作用明显好于感病品种;炭疽病菌可诱导黄瓜有效抑制褐斑病的发生,但挑战接种褐斑病菌后,却促进了炭疽病的发生.诱导接种炭疽病菌后再挑战接种褐斑病菌12d,对褐斑病的防效为92.07%.     

Genetic analysis of ORF5 of recent Korean porcine reproductive and respiratory syndrome viruses (PRRSVs) in viremic sera collected from MLV-vaccinating or non-vaccinating farms

The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea.     

猪场生物安全体系中十个通道的设计应用

2018年8月开始,非洲猪瘟在我国快速多点发生,该病是高度接触性传染性疾病,目前无有效的疫苗和药物控制,各大公司和养殖户开始了猪场生物安全体系的升级改造。两年后我国大部分猪场的成功复产,全国生猪出栏量的大幅提升,证明了生物安全措施巨大效力;同时在严格的生物安全措施下创新了精准剔除、快速复产等操作,进一步证明了生物安全措施的有效作用。文章主要介绍猪场生物安全体系中入口(大门)和出口(后门)最为关键防线处的通道设计,方便所有的生物安全操作能够高效落实,切断病原轻易进出猪场的途径。