实行科学养蚕促进叶丝转化

蚕桑是淳安县四大农业支柱产业之一,近年来发展迅速,而且茧质综合指标一直名列全省前茅,"千岛湖"牌茧丝在省内外市场有良好声誉.为进一步提高千岛湖牌茧丝质量效益,笔者经分析研究,认为该县蚕茧的一茧丝长指标还有很大潜力.以春茧为例,该县1993～2003年的11年中,平均一茧丝长为1 098.59m,而在生产实践中养蚕比较好的一茧丝长都在1 200m以上,说明广大蚕农在科学养蚕上还存在较大差距,如小蚕饲养加温、5龄盛食期给叶、上蔟适时的选择、养蚕场地、养蚕劳动力素质等差异,影响了蚕儿桑叶食下量,导致蚕茧干壳量高低不一,反映到一茧丝长指标上不够理想.为使该县蚕茧一茧丝长有较大提高,促进茧质更上一层楼,现提出以下技术改进措施.     

影响冻干乳酸菌存活性的相关因素

本文综述冻干乳酸菌发酵剂制备中相关因素对冷冻干燥和贮藏期间乳酸菌存活率的影响，包括内在因素、生长因素、非致死性处理、干燥介质、贮藏和复水等方面因素。     

复方罗红霉素可溶性粉对鸡葡萄球菌病的疗效试验

采用人工诱发的病理模型,按推荐剂量治疗,验证复方罗红霉素可溶性粉对鸡(试验时30日龄)葡萄球菌病的疗效.试验结果表明,复方罗红霉素可溶性粉对鸡葡萄球菌病有很好的治疗效果,有效率达96.7%;推荐剂量治疗组的死亡率极显著地低于感染对照组(P<0.01);推荐剂量治疗组与健康对照组的增重差异不显著(P>0.05),但极显著高于感染对照组(P<0.01).     

豆科牧草追施钾肥试验

试验结果表明，当旱地红壤养分中的速效钾含量在７５．５ｐｐｍ情况下，白三叶每公顷追施氯化钾２２５ｋｇ，结果施肥比对照每公顷增产鲜草７７７９ｋｇ，每公顷氯化立鲜草３４．６ｋｇ，增产率达２９％。按生物统计ｔ测验，增产显著。当稻田速效钾含量在４５ｐｐｍ条件下，给紫云英每公顷施用氯化钾１１２．５ｋｇ，结果施肥比对照每公顷增产鲜草５０００－７７５０ｋｇ，平均每公顷增产６７５０ｋｇ。每公斤钾肥可增产粮食２３．５     

Immune responses of orange-spotted grouper,Epinephelus coioides,against virus-like particles of betanodavirus produced in Escherichia coli

Betanodaviruses are the causative agents of viral nervous necrosis (VNN), a serious disease of cultured marine fish worldwide. Virus-like particles (VLPs) are one of the good novel vaccine candidates to control this disease. Until now, betanodavirus vaccine studies mainly focused on the humoral immune response and mortality after virus challenge. However, little is known about the activation of genes responsible for cellular and innate immunity by vaccines. In the present study, VLPs of orange-spotted grouper nervous necrosis virus (OGNNV) were produced in prokaryotes and their ability to enter Asian sea bass cells was the same as native virus, suggesting that they possess a similar structure to OGNNV. VLPs immunogenicity was then determined by intramuscularly vaccinating Epinephelus coioides at different concentrations (1.5 or 15 μg g^?1 fish body weight, FBW) and immunizing frequencies (administration once, twice and thrice). A single vaccination with the dosage of 1.5 μg g^?1 FBW is enough to provoke high titer antibodies (average 3 fold higher than that of negative control) with strong neutralizing antibody titer as early as 1 week post immunization. Furthermore, quantitative PCR analysis revealed that eleven genes associated with humoral, cellular and innate immunities were up-regulated in the liver, spleen and head kidney at 12 h post immunization, correlating with the early antibody response. In conclusion, we demonstrated that VLP vaccination induced humoral immune responses and activated genes associated with cellular and innate immunity against betanodavirus infection in orange-spotted grouper.     

Lysine restriction and realimentation affected growth,blood profiles and expression of genes related to protein and fat metabolism in weaned pigs

To investigate the effects of lysine restriction and subsequent realimentation on growth performance, blood profiles and gene expression of leptin and myostatin, 128 weaned pigs [initial body weight (BW) 6.96 ± 1.07 kg, 26 ± 2 days of age] were randomly allotted to four treatments. The starter diets during the first 2 weeks (P1) contained 100%, 80%, 70% or 60% of recommended lysine levels ( National Research Council, 1998 ). Then, common grower 1 and 2 diets were offered for 2 weeks (P2 and P3) each. During P1, average daily gain (ADG) was linearly reduced (p < 0.05) with the increasing levels of lysine restriction. Growth rate was greater in pigs previously fed lysine‐restricted diets than well‐fed pigs although it did not reach a significant level during realimentation. However, the final BW and overall ADG were the lowest (p < 0.05) and F/G was poor in pigs fed 60% lysine diet. Relative visceral organ weights and composition of skeletal muscle were similar (p > 0.05) among the treatment. Blood triglyceride and glucose levels were increased (p < 0.05) during P1, while blood urine nitrogen, total protein and albumin levels were decreased (p < 0.05) during P2 with the reduction in dietary lysine levels. The abundance of myostatin mRNA in skeletal muscle and leptin mRNA in subcutaneous adipose tissue were lower (p < 0.05) in lysine‐restricted pigs than in pigs fed non‐restricted diets. In conclusion, 80% and 70% lysine restriction of starter diets resulted in inferior growth and compensatory growth effect was noted during realimentation, while 60% lysine restriction had a negative influence on growth performance. Moreover, the changes in myostatin and leptin mRNA abundance caused by nutritional manipulations may be involved in the regulation of protein and fat deposition in young pigs.     

Impact of cold-season grazing and supplementary feeding on rumen metabolic parameters and micro-organisms in the ewes of Gansu Alpine Fine Wool Sheep北大核心CSCD

An experiment was conducted to scientifically identify the appropriate feed for Gansu Alpine Fine Wool ewes in order to change the animals' breeding mode, which currently can only be mated at the age of 2.5 years due to insufficient nutritional supply. The experiment selected 48 12-month-old ewes and randomly divided them into group a (Diet 1), group b (Diet 2), group c (Diet 3), and a control group with no supplementary feeding. The feed test was run for 90 days. The rumen pH of groups a and b were very significantly higher (P<0.01) or group c significantly lower (P<0.05) than control group. The rumen ammonia nitrogen, protein nitrogen and total nitrogen of groups a, b and c were all higher than control group (P<0.01). The total volatile fatty acids of group a and b were all higher than the control group (P<0.01), group b significantly higher than group c (P<0.05). The molar ratio of acetic acid and propionic acid in group a was very significantly higher than control group (P<0.01), group b and c were significantly higher than control group (P<0.05). The molar ratio of butyric acid in group a was very significantly higher than group c (P<0.01). The ratio of acetic acid and propionic acid in group b was significantly lower than control group (P<0.05). The number of several rumen fiber-degrading bacteria and protozoa in groups a, b and c were very significantly (P<0.01) or significantly (P<0.05) higher than the control. In conclusion, this study shows that supplementary feeding can positively affect the rumen metabolic parameters and the number of several rumen microorganisms in Gansu Alpine Fine Wool ewes. In general, the effects of Diet 1 were the strongest, while Diet 2 also produced notable improvements. © 2018, Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

湖南省某生猪批发市场疫病传播风险评估

为评估湖南省某生猪批发市场猪群疫病的发生风险,找出可能的风险因素,便于提出针对性预防措施,采用自行设计的调查问卷,结合访谈和现场调查,对27户经营户进行了调查,并将调查结果和调运数据相结合进行了疫病传播风险定性评估。结果显示:该市场疫病传入的可能性"高",内部传播的可能性"中等",疫病传出的可能性"高"。生猪调运频次多、数量大,经纪人行为复杂,运输车辆清洗消毒不彻底是可能的风险因素。评估结果提示,应尽量减少经纪人行为影响,重点加强对运输车辆的清洗消毒。     

赤霉素对沙枣种子发芽率与出苗率的影响

研究了不同浓度GA3对沙枣(Elaeagnus angustifolia)种子发芽率和出苗率的影响。结果表明,在50～150 mg·L-1范围内,不同质量浓度的GA3对沙枣种子发芽和出苗均有显著促进作用（P＜0.05）,质量浓度为100 mg·L-1时效果最好,室内发芽率为86.3%,圃地出苗率为73.6%。     

1株犬副流感病毒的分离鉴定及生物学特性研究

试验旨在分离鉴定犬副流感病毒(canine parainfluenza virus,CPIV),并对其生物学特性进行研究。用Vero细胞接种感染CPIV阳性犬肺脏组织,盲传4代,收集72 h病毒液进行RT-PCR鉴定、电镜观察、血凝试验、热敏性试验、紫外照射试验及病毒一步生长曲线的测定,同时扩增N基因进行序列分析,并构建系统进化树。结果显示,试验成功从出现咳嗽、流鼻涕等呼吸系统疾病症状的病犬肺脏中分离出1株CPIV,命名为CPIV-BJ01;RT-PCR扩增结果发现,在534 bp处有特异性目的条带。病毒电镜观察发现,其超微结构呈圆形、有囊膜、直径在80～200 nm之间;血凝试验显示,病毒在4和37℃均能凝集1%猪红细胞,与报道的CPIV血凝特性一致;病毒对热敏感,长时间高温下病毒毒价会随之下降;紫外照射可使病毒在短时间内对细胞的感染性急剧下降。病毒一步生长曲线测定结果显示,在12～48 h病毒高速增殖,细胞培养液中病毒滴度急剧上升,之后趋于稳定。CPIV N基因序列与19株有代表性的副流感病毒N基因相比,其核苷酸序列同源性为97.1%～99.8%。遗传进化分析表明,CPIV-BJ01与PIV5 1168-1(登录号:KC237064.1)和PIV5 ZJQ 221(登录号:KX100034.1)位于同一分支上,亲缘关系较近。