两种饲喂方式对哺乳母猪生产性能的影响研究

选取年龄、胎次、品种基本一致的哺乳母猪20头,随机分成对照组和试验组,试验分两批进行,每批10头.在相同的环境条件下,母猪自由饮水,饲喂同一哺乳母猪料.母猪分娩后4 d内,采用原场饲养制度,逐步增加哺乳母猪采食量,第5天开始,对照组采用不限量饲喂,试验组采用限量和添加哺乳母猪补充料的饲喂方式,仔猪21日龄断奶.结果显示两组仔猪21日龄的断奶窝重、母猪断奶后再发情时间和母猪哺乳失重等差异均不显著(P>0.05).     

Molecular Weight: Measurements with Gravity Cells

A gravity cell can be used to determine the weights of particles greater than 10(8) molecular weight units. The solution is maintained at a temperature which is constant to +/- 0.001 degrees C until equilibrium between sedimentation produced by gravity is balanced by back diffusion. The weight-average molecular (particle) weight of tipula iridescent virus was (1.05 +/- 0.02) x 10(9).     

林业发展所面临的形势及国民经济发展对林业的需求分析

文章着重分析了内蒙古当前林业发展形势及国民经济发展对林业的需求 ,并客观的论述了自治区林业发展的有利条件和制约因素 ,希望能够对今后的林业建设有所帮助 ,从而把握机遇 ,加快环境建设步伐 ,早日改善环境状况。     

Structural and Functional Events on the Porcine Zona Pellucida During Maturation, Fertilization and Embryonic Development: a Scanning Electron Microscopy Analysis

Porcine oocytes and pre-implantation embryos from the same, as well as from different animals, have an extremely heterogeneous morphology of the zona pellucida (ZP) surface, as shown by scanning electron microscopy. For years, it has been believed that this heterogeneous morphology plays an important role in the sperm-oocyte interaction. The aim of this study was to analyse the zona morphology and sperm-binding patterns on the porcine ZP. Oocytes were divided into four categories: immature, matured in vivo, or matured in vitro over a time period of 24 or 48 h. The zona morphology of early embryos grown in vivo or in vitro was also investigated. Four different types of zona morphology were detectable. They ranged from a porous, net-like structure to a nearly smooth and compact surface. No correlation could be established between the different kinds of maturation in terms of these zona types. All oocytes exhibited extremely heterogeneous zona morphologies, with no clear trend. During subsequent in vivo embryo development, the zona surface changes from a porous structure to one with a compact surface, while the morphology of in vitro embryos remained compact at all stages of development. The analysis of the number and distribution patterns of spermatozoa trapped in the ZP revealed extremely variable patterns, regardless of the zona morphology. Differences were only present if sorted or unsorted spermatozoa were used for insemination. Regardless of the number of inseminated spermatozoa after sorting, only a few (1-2) could be detected on the ZP. Whether oocytes were matured in vivo or in vitro was not a relevant factor. Unsorted spermatozoa bound in higher numbers than sorted ones. The number was directly dependent on the number of spermatozoa used for insemination.     

Molecular Pumping

A method is described for producing high vacua. A magnetically suspended molecular pumping rotor is operated inside a sealed glass vacuum system. The system is free of lubricants and can be baked out. The system gives promise of producing pressures below those previously used.