Estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis in a sample of Minnesota dairy herds using bacterial culture of pooled fecal samples

The objective of this study was to describe the estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis (Map) in a sample of infected dairy herds in Minnesota (N = 66) using test results from bacterial culture of pooled fecal samples. Fecal samples were collected from up to 100 cows in each herd and were tested using bacterial culture in pools of 5 cows based on age order. The mean herd size was 222 (44 to 1500) milking cows; the cows were predominantly Holstein. Using a frequentist approach, the within-herd mean individual fecal prevalence was 10% [95% confidence interval (CI) = 4% to 16%] assuming 70% test sensitivity and 99.5% test specificity. Using Bayesian methods, the estimated true within-herd individual cow prevalence was 14% (95% CI = 7% to 27%). Within-herd prevalence was higher in larger dairy herds than in herds with fewer cows. As Map is the causative agent of Johne's disease (JD), the results of this study could contribute to the success of a nationwide control program for this disease.     

A method to provide improved dose-response estimates for airborne pathogens in animals: an example using porcine reproductive and respiratory syndrome virus

This paper describes a method to provide improved probability estimates that exposure to a specific dose of an airborne infectious pathogen will result in animal infection. Individual animals were exposed to a specific dose of airborne pathogen. Following exposure, animals were individually housed and monitored for evidence of infection. The detection of specific antibodies and/or the pathogen in diagnostic specimens was evidence that the exposure dose resulted in infection. If replicated over a range of doses, the results can be used to derive a dose-response curve for a variety of animal species and infectious pathogens. This information is useful in estimating the likelihood of infection associated with exposure to airborne infectious microorganisms. Applications include predicting the risk of transmission associated with exposure to airborne pathogens, modeling the transmission of airborne pathogens, and determining requirements for effective exposure doses for vaccines delivered in aerosols.     

辽宁绒山羊改良当地蒙藏山羊试验效果观察

用辽宁绒山羊改良引进的内蒙古白绒山羊与甘南当地藏山羊,结果表明：辽蒙藏杂交F1代绒山羊,在初生、3月龄、6月龄、12月龄各个时期,其体重、体高、体长、胸围与对照组（蒙藏山羊杂交后代）相比,公羊除初生和3月龄羔羊的体长、12月龄胸围差异不显著外（P〉0．05）,其它均极显著的高于对照组;母羊的3月龄、12月龄体重与对照组差异极显著（P〈0．01）,初生、6月龄体重差异显著（0．01〈P〈0．05）,初生、3月龄、6月龄体高、胸围及6月龄体长与对照组差异极显著（P〈0．01）,公、母羊绒细度、长度、单纤维断裂强力、单纤维断裂伸长率等指标差异不显著（P〉0．05）,含绒率和产绒量差异极显著（P〈0．01）。杂交F1代羊杂交优势明显,效果显著。     

抗鸡新城疫卵黄抗体IgY的研制

产蛋母鸡经新城疫灭活抗原重复免疫后，所产生的高免卵黄中，特异性抗体的HI效价可达到12log2以上。从高免卵黄中分离提纯的特异性新城疫抗体，病毒中和试验结果表明，具有明显的中和病毒的作用，特异性病毒中和指数可达到630957以上。使用纯化后的高免卵黄抗体(IgY)安全、高效、无任何不良反应。     

苜蓿不同密度种植生长状况及经济效益分析

随着我国畜牧业的快速发展,饲草料的需求量大幅度增加,优质饲草料作物高产栽培的研究也在不断加强。环京南地区优质饲草的种植十分缺乏,以合理的密度种植苜蓿可以提高单位土地的产出量、获得较高的经济收益,对于农区种植饲草具有指导意义。     

钙渗透对甜樱桃果实采后生理的影响

减压渗Ｃａ￣（２＋）能够明显增加甜樱桃果实中Ｃａ￣（２＋）含量。果实中Ｃａ￣（２＋）含量与贮藏后期维生素Ｃ含量成显著正相关，而与可溶性固形物含量无关。Ｃａ￣（２＋）能够抑制果实中ＰＯＤ（过氧化物酶）、ＰＰＯ（多酚氧化酶）活性，并且随浓度增加抑制作用增强，Ｃａ￣（２＋）含量与ＰＰＯ活性成显著负相关。Ｃａ￣（２＋）处理果实腐烂率比对照降低３８．８％－１００％，褐变率降低１３．３８％－４５．２３％。     

菌物学家科海萍踪

八九　马拉丘克 (ＮｉｃｈｏｌａｓＭａｌａｊｃｚｕｋ) 现代澳大利亚菌根学家 ,现任Ｍｏｒｄｏｃｈ大学教授。他是近年来活跃在国际菌根学的佼佼者 ,对地下真菌的研究颇有造诣和建树 ,对比菌种和树种的不同组合及进行生态多样性的研究。在地下菌的石肉菌科(Ｍｅｓｏｐｈｅｌｌ     

结球甘蓝耐裂球性状遗传分析

 以结球甘蓝‘79-156’和‘96-100’为亲本配制的6 个联合世代（P1、P2、F1、B1、B2、F2）群体为试材,采用主基因+ 多基因混合遗传模型对耐裂球性状进行了遗传分析。两年结果均表明,耐裂球性状的最适遗传模型为E-0 模型,即两对加性–显性–上位性主基因+ 加性–显性–上位性多基因控制。两对主基因均以加性效应为主,且存在明显的互作效应。2010 年该组合B1、B2、F2 分离群体的主基因遗传率分别为67.3%、1.4%和59.1%,多基因遗传率分别为0、56.2%和0,遗传变异平均值占表型变异的60.9%,环境变异平均值占表型变异的39.1%;2011 年该组合B1、B2、F2 分离群体的主基因遗传率分别为85.5%、22.3%和84%,多基因遗传率分别为0、24.3%和0,遗传变异平均值占表型变异的63.9%,环境变异平均值占表型变异的36.1%。表明该性状以主基因遗传为主,同时受环境影响较大,应在早期世代进行选择,B1、F2 主基因选择效率较高     

早春保护地番茄易发病害的识别及防治技术

早春日光温室或大棚番茄,以其产量高、上市早、售价高等优势,被广为栽培。但近来不少菜农反映,他们种植的番茄病害较多,有的已给生产造成巨大损失。针对菜农的上述问题,现把早春保护地番茄生产中易发病害的特点及其防治技术给以总结。