加拿大双低菜粕对奶牛产奶性能的影响

试验主要研究了加拿大双低菜粕对奶牛产奶性能的影响,为加拿大双低油菜籽粕在奶牛生产中的科学应用提供理论依据和实践指导。试验采用单因素完全随机设计,选择32头荷斯坦奶牛,按年龄、体重、胎次、泌乳期与产奶量随机分组。试验包括2部分。第一部分,日粮粗蛋白含量为14.5%,将16头奶牛随机分为对照组与双低菜粕组,每组8头牛,对照组不饲喂双低菜粕,双低菜粕组在精饲料中添加10%的双低菜粕,替代精饲料中全部的豆粕和棉粕。第二部分,日粮粗蛋白含量为12.5%,将16头奶牛随机分为对照组与双低菜粕组,每组8头牛,对照组不饲喂双低菜粕,双低菜粕组在精饲料中添加5%的双低菜粕,替代精饲料中全部的豆粕和棉粕。试验期75 d,其中预饲期15 d,正饲期60 d。结果表明:蛋白含量为14.5%的双低菜粕组可以提高产奶量,在整个试验期内,平均每头奶牛每天多产奶0.76 kg,对乳成分没有显著影响(P0.05),与对照组相比,双低菜粕组的平均乳脂量、乳蛋白量显著增加(P0.05)。在奶牛日粮中蛋白含量为12.5%时,双低菜粕组对奶牛产奶性能没有显著的影响(P0.05)。因此合理使用加拿大双低菜粕提高奶牛产奶性能,从而提高经济效益。     

饲料中霉菌毒素的危害及脱毒方法

饲料及其原料在加工、储存和运输过程中容易发生霉变,霉菌不仅污染饲料,而且消耗饲料中的营养物质,使饲料品质下降。畜禽摄食了受霉菌毒素污染的饲料之后容易出现中毒、腹泻、生长和繁殖性能下降等症状,严重情况下可能导致死亡。文章就霉菌毒素危害及近年来国内外饲料霉菌毒素脱毒技术研究进展进行综述,旨在为饲料中霉菌毒素的脱毒处理提供参考。     

基层常规动物防疫模式初探

本文结合庄浪县动物防疫实际,经积极探索完善,从组织形式、防疫模式、工作方法、服务保障四个方面,总结出基层动物防疫基本模式,为基层动物防疫的规范化、程序化、标准化提供可复制的方法和思路。     

癸氧喹酯干混悬剂防治人工感染鸡球虫病的效果试验

通过对14日龄岭南黄鸡人工感染柔嫩艾美耳球虫卵囊,测定国家四类新兽药癸氧喹酯干混悬剂的抗球虫作用。研究结果表明,新兽药癸氧喹酯干混悬剂按照推荐剂量0.25g/L(15mg/L)饮水给药对鸡球虫病表现出高效的抗球虫活性,具有良好的预防鸡球虫病效果,达到100%的保护率,抗球虫指数高达202.2。     

四种核酸染料对用LAMP方法检测猪繁殖与呼吸综合征病毒的影响

本研究旨在建立一种基于颜色变化的北美洲型猪繁殖与呼吸障碍综合征病毒(PRRSV)RT-LAMP检测方法及结果判定方法,方便LAMP技术的现场检测应用。根据Gen Bank中美洲型PRRSV的保守序列设计一套LAMP引物,对反应进行优化后建立了PRRSV LAMP检测方法。对比Dye63、钙黄绿素(Calcein)、SYBR Green I和Picogreen 4种核酸染料对于LAMP反应的适用性。结果显示,只有Calcein、Dye63适于LAMP反应前加入,但对扩增效率均产生一定抑制,造成反应时间延迟:Calcein的延迟作用更强(约10min),Dye63延迟作用较小(约5min)。加入Dye63的LAMP反应灵敏度为2×101拷贝,而加入Calcein的灵敏度要低10倍。经多功能酶标仪对荧光强度的检测,含Dye63的反应阴阳性差异明显,可用于LAMP反应结果的判定。据此建立的基于新型核酸染料Dye63的PRRSV RT-LAMP检测方法操作简单、方便、直观,可大大减少环境污染造成的假阳性。Dye63有望成为继Calcein之后,可用于LAMP反应前加入,反应后闭管判定的一种新核酸染料,方便LAMP检测技术现场应用。     

小型生猪屠宰场“瘦肉精”检测中存在的问题及对策

本文针对当前县区小型生猪屠宰场“瘦肉精”现场快速检测中存在的采样随意、检测粗略、抽样单填写不规范等问题,从规范采样和检测过程的角度提出对策,为提升县区小型生猪屠宰场“瘦肉精”快速检测的科学性和规范性提供参考。     

一株小反刍兽疫病毒的分离鉴定与生长曲线测定

将含高滴度小反刍兽疫病毒的新鲜病料研磨后接种VERO DS细胞系进行病毒分离,出现细胞病变后连续传代,取3代以上培养物,进行RT-PCR和间接免疫荧光试验及生长曲线测定。生长曲线测定分别以0.01和0.1 MOI接种VERO DS细胞,每隔12h测定病毒滴度,连续培养168h,绘制病毒生长曲线,分析生长特性。结果显示,病料接种细胞72h后,出现细胞病变,经RT-PCR和间接免疫荧光试验鉴定为小反刍兽疫病毒?;生长特性研究显示,0.01和0.1 MOI两种病毒接种量,病毒滴度最高均为106 TCID50左右,但峰值出现时间和下降速度存在差异,0.01 MOI接种量出现峰值晚,但是维持高滴度时间较长。本文成功分离一株小反刍兽疫病毒,并对两种接毒量的生长特性差异进行了初步分析,为探索该病毒培养方法和收毒时间提供了借鉴。     

仔猪雷极氏普罗菲登斯菌的分离鉴定及系统进化分析

为了解猪雷极氏普罗菲登斯菌(P.rettgeri)的生物学特性、致病性及16SrRNA基因系统进化关系,从发生严重腹泻、血便的哺乳仔猪群的内脏器官中分离到1株病原菌,根据形态特征、培养特性、生化特性、16SrRNA基因序列分析鉴定为P.rettgeri。小鼠攻毒试验证实,该分离菌株对试验小鼠有较强致病力,哺乳仔猪回归试验可复制出与临床上相似的典型症状,并从发病死亡小鼠及哺乳仔猪中分离到攻毒菌株。系统进化分析表明,分离菌株与雷极氏普罗菲登斯菌系统进化关系最为密切,其16SrRNA基因序列与雷极氏普罗菲登斯菌代表菌株的同源性在97.3%~99.6%之间。药敏试验结果表明,分离菌株对头孢哌酮钠、头孢噻肟钠、头孢曲松钠、头孢唑啉、头孢呋肟、头孢吡肟、阿莫西林、链霉素、氨曲南、诺氟沙星、左氟沙星、恩诺沙星、卡那霉素、氨苄青霉素、米诺环素、链霉素、阿米卡星等多数药物敏感。首次报道了雷极氏普罗菲登斯菌可以引起哺乳仔猪严重腹泻,提示在仔猪腹泻中应注意该菌感染的诊断、监测和防控。     

Impact of Endocrine‐Disrupting Chemicals on Reproductive Function in Zebrafish (Danio rerio)

The prevalence of endocrine‐disrupting chemicals (EDCs) in the aquatic environment has been associated with the wide detection of alterations in the development and physiology of vertebrates. Zebrafish, as a model species, has been extensively used in toxicological research. In this review, we focus on recent published evidence of the harmful effects of EDCs on reproductive function in zebrafish, including skewed sex ratio, immature gonads, diminished sexual behaviour, decreased sperm count, reduced spawning and fertilization. These impairments mostly result from disruption to sex‐steroid hormones induced by endocrine disruptors. We also discuss other effects of exposure to EDCs. In EDC exposure research, despite incomplete assessments of altered gonad histopathology and sexual behaviour, these present potential effective biomarkers or pathways for evaluating the reproductive function in zebrafish on EDC exposure. To date, the pernicious effects of some EDCs on the reproductive performance in laboratory zebrafish are well understood; however, similar alterations remain for further determination in wild‐type fish and more kinds of EDCs. More studies should be performed under established scientific regulatory criteria to investigate the impact of EDCs on reproduction in zebrafish. Moreover, further research is required to explain the definite mechanism of sexual differentiation, which helps in understanding the shift of sexual phenotype with EDC exposure.     

Impact of relationships between test and training animals and among training animals on reliability of genomic prediction

One of the factors affecting the reliability of genomic prediction is the relationship among the animals of interest. This study investigated the reliability of genomic prediction in various scenarios with regard to the relationship between test and training animals, and among animals within the training data set. Different training data sets were generated from EuroGenomics data and a group of Nordic Holstein bulls (born in 2005 and afterwards) as a common test data set. Genomic breeding values were predicted using a genomic best linear unbiased prediction model and a Bayesian mixture model. The results showed that a closer relationship between test and training animals led to a higher reliability of genomic predictions for the test animals, while a closer relationship among training animals resulted in a lower reliability. In addition, the Bayesian mixture model in general led to a slightly higher reliability of genomic prediction, especially for the scenario of distant relationships between training and test animals. Therefore, to prevent a decrease in reliability, constant updates of the training population with animals from more recent generations are required. Moreover, a training population consisting of less‐related animals is favourable for reliability of genomic prediction.