Retrospective analysis of trends and production factors associated with sow mortality on swine-breeding farms in USA   总被引：2，自引：0，他引：2  

Koketsu Y 《Preventive veterinary medicine》2000,46(4):249-256

Of the 825 pig farms in USA that mailed in their electronic file containing production records, 604 farms were used to observe breeding-female mortality risk and related factors (herd size, lactation length, parity and season). Multiple regression was used to determine factors associated with annual mortality risk. Analyses of variance were used for comparisons of mortality risks among parity and season groups. Average annual mortality risks during the 1997 period was 5.68%. Average breeding-female inventories and average lactation length on USA farms were 733 and 18.3 days, respectively. Higher annual breeding-female mortality risk was associated with larger herd size, greater parity at farrowing and shorter lactation length (P<0.02). For example, as herd size increases by 500 females, mortality risk increases by 0.44%. Older parity was associated with higher mortality risks. Summer season was also associated with higher mortality risk. Using five-years’ records on 270 farms, annual mortality risk in 1997 was higher than those of 1993 and 1994, while average breeding-female inventory increased and lactation length decreased. It is recommended that producers, especially in large herds, pay more attention to breeding females.  相似文献   

影响山羊胚胎冷冻效果因素的研究   总被引：4，自引：0，他引：4  

李雪松  桑润滋  李俊杰  张国磊  孙树春 《畜牧与兽医》2006,38(2):9-12

分别用浓度为1.5 mol/L的乙二醇(EG),1.5 mol/L 1,2-丙二醇(PROH)和1.5 mol/L甘油为冷冻保护液对山羊胚胎进行常规冷冻保存,结果三者对山羊胚胎的冷冻保护效果无显著差异,其中以1.5 mol/L EG的冷冻保护效果为佳。以EFS40为玻璃化液对山羊胚胎进行细管法和OPS法玻璃化冷冻,其结果与常规冷冻间差异不显著,表明常规冷冻法、玻璃化细管法和OPS法均可用于山羊胚胎的冷冻保存。采用25℃和37℃水浴对常规冷冻和玻璃化冷冻后的山羊胚胎进行解冻,从解冻后的发育效果看,二者间无显著差异,但37℃水浴解冻后的胚胎发育效果略好于25℃。还比较了玻璃化液EFS40中添加FCS和BSA后与不添加其他成分的EFS40对胚胎冷冻保护效果的影响,结果表明添加BSA的EFS40的冷冻保护效果显著地高于不添加其他成分的EFS40,但与添加FCS的EFS40间不存在统计学上的差异。  相似文献   

冷冻方法和冷冻保护液对山羊卵母细胞发育的影响     

李雪松  桑润滋  李俊杰  孙树春 《中国兽医学报》2007,27(2):270-273

比较了不同冷冻方法和冷冻保护液对山羊卵母细胞冷冻-解冻后体外受精和激活后的发育效果.结果表明,开放式拉长塑料细管(OPS)法的效果好于玻璃化细管法和常规冷冻法;在OPS法中,20%EG 20%DMSO对卵母细胞的冷冻保护效果好于EDFS40,而在玻璃化细管法冷冻中,则是EDFS40好于20%EG 20%DMSO.对于常规冷冻法而言,则是1.5mol/L EG的冷冻效果好于1.5mol/L PROH.  相似文献   

台湾中部地区短延时降雨强度初步探讨     

赵怡婷  李锦育* 《亚热带水土保持》2012,(1):1-6

台湾地区在经历1999年的921地震后,山坡地土体松动严重,仅仅短延时的降雨即有机会引起土石流的发生,而近年微小的降雨条件下即有可能触动土石流发生,因此将台湾中部地区14个测站所测得的台风降雨资料,依照台风降雨强度进行水文频率分析,分析方法采用对数常态分布法、极端值第一类分布法、皮尔逊第三类分布法及对数皮尔逊第三类分布法等4种方法,计算短延时重现期距并绘成降雨强度-延时-频率之分析曲线,再整合各区域土石流潜势溪流的分布情况,分析台风降雨对台湾中部地区所造成之影响.  相似文献   

Duration of load effects of solid wood: A review of methods and models     

《Wood material science & engineering》2013,8(3-4):115-124

Abstract

Test methods for studying the effect of long-term loading on the load-carrying capacity of structural wood are discussed. The impact of sampling procedures on test results is investigated and is exemplified. It is concluded from this investigation that the sampling method has a significant impact on the test results. A number of mathematical models for estimation of the effect of load duration are also presented and brief outlines of the theoretical background for five categories of models are given. No attempt is made to compare the models in order to nominate the best model. Effort is, however, made to illustrate the futility of calibrating models against one type of test when the model is redundant to the test type.  相似文献   

《延边大学农学学报》发展简史     

朴基炳 《延边大学农学学报》2004,26(1):70-76

简述了《延边大学农学学报》创刊以来4个阶段的发展史．  相似文献   

Burial rates of surrogate seeds in arable fields     

P R WESTERMAN‡  P M DIXON†  & M LIEBMAN 《Weed Research》2009,49(2):142-152

The probability of seed consumption by surface-dwelling predators depends on the duration of seed exposure on the soil surface. We investigated seed burial using painted ceramic beads as surrogate seeds. Fifty beads of three size classes each were applied to small arenas within crop fields and their fates were followed from August to October. New sets of beads were applied as soon as most beads had disappeared from the soil surface. Bead availability on the soil surface declined immediately after placement, and then declined steadily over time, with increased loss during rain and management practices. Smaller beads were incorporated into the soil/litter matrix more easily than larger beads. Bead burial differed considerably among crop environments, with more burial in forage crops (red clover, lucerne) than in row crops (soyabean, maize). The fact that seed availability differed among crop environments suggests that it can be manipulated to maximise predation risk.  相似文献   

棉花黄萎病菌鉴定技术进展   总被引：9，自引：1，他引：8  

陈旭升  陈永萱  黄骏麒 《棉花学报》1997,(2)

黄萎病作为一种危害严重的世界性病害，如何快速有效地鉴定黄萎病菌已成为当今学术界普遍关心的问题。本文综述国内外有关黄萎病菌鉴定技术的发展动态，旨在为从事棉花黄萎病研究的科学工作者提供可资借鉴的研究信息  相似文献   

森林人家休闲健康旅游发展对策     

林道茂 《福建林业科技》2007,34(2):219-220,229

从创新休闲模式,提升产业结构的理念出发,提出发展森林人家亟待解决的问题和对策。  相似文献   

我国森林经营方案问题研究评述   总被引：6，自引：2，他引：6  

韦希勤 《林业调查规划》2007,32(5):105-108

回顾了森林经营方案编制的历史,较全面地阐述了森林经营方案在编制、实施与管理中存在的问题.指出了编制与实施森林经营方案在理论上与技术工作中需要进一步研究解决的问题.对森林经营方案编制的发展趋势进行了初步分析.  相似文献