共查询到20条相似文献，搜索用时 453 毫秒
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繁殖是养猪生产过程中的关键一环 ,该环节成功与否直接影响整个养猪业的经济效益。传统数量遗传学在指导家畜育种中起到了重要的作用 ,但是繁殖性状遗传力低、性状表现晚、而且是限性遗传 ,通过常规选择难以有所进展。中国猪 ,尤其是太湖猪 ,以其超高繁殖率闻名于世 ,国内外学者对其高繁殖性能的遗传机制进行了研究 ,提出了窝产仔数主效基因假说 ,并通过候选基因法、基因组扫描法等方法进行了研究 ,期望找到控制产仔数的主基因 ,从而为猪繁殖性状的遗传改良提供了新的途径。目前太湖猪窝产仔数主效基因探索已有成功的报道 ,本文将对猪高繁殖… 相似文献
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郭建凤 《河南畜牧兽医(综合版)》2004,25(4):5-6
母猪繁殖性能高低是决定整个猪场经济效益的关键。产仔数是猪繁殖性状中最重要的性状,由于母猪窝产仔数的遗传力低(0.05～0.30),所以通过表型选择来提高母猪窝产仔数,效果不显著。为此,人们希望探索窝产仔数指标选择以外的途径来提高母猪的产仔数。针对这一问题,国内外的许多养猪学者都对与窝产仔数有关的因素如子宫容积、子宫内膜毛细血管的分析、胎盘重量等进行了大量的研究。最近研究得出母猪胎盘效率不同会对其产仔数有很大的影响,即母猪胎盘效率高的,其窝产仔数就高,胎盘效率低的,其窝产仔数就低。母猪胎盘效率就是指仔猪出生窝重与胎… 相似文献
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猪胎盘效率与繁殖性能的关系 总被引：5，自引：0，他引：5
本文综述了猪高繁殖力的生理机制研究进展，对近年来关于猪胎盘效率与产仔数关系以及胎盘效率与生产性状间的关系研究进行了详细描述，从胎盘效率这一综合指标探讨猪高繁殖力的生理基础。目前的研究结果表明，基于胎盘效率的选择是提高猪的窝产仔数行之有效的方法。 相似文献
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母猪的繁殖性能一直是猪育种专家研究的热点，而猪的窝产仔数更是关注中的焦点。由于母猪窝产仔数的低遗传力（平均0．15）和负的母体效应，多年来通过表型选择直接提高母猪的窝产仔数的途径没有获得大的进展。法国用了30年改良这个性状收效甚微，丹麦花费50年时间才将每胎产仔数提高1．0头。随后人们希望通过对影响产仔数的生理因素如排卵数、胚胎存活率、子宫容积等进行选择来加以提高。 相似文献
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猪的产仔数是繁殖性状中重要的经济性状,直接关系到养猪业的经济收益。英国动物育种学家Chris Haley曾估算,如果每头母猪的产活仔数每胎提高I头,英国的养猪业每年就可增加利润7亿英镑,整个欧盟养猪业可多获利20亿英磅。在我国,如果母猪产仔数每胎提高1头,每年也将增收190亿人民币的纯利。因此,通过候选基因法寻找控制猪产仔数的主效基因或遗传标记,以及通过标记辅助选择提高猪的产仔性能,是目前猪遗传育种研究的热点之一。在过去的半个世纪里,通过常规育种技术,猪的许多重要生产性状都在遗传上得到了很好的改良（如瘦肉率,背膘厚）,但对产仔数的改变却十分有限,主要原因是产仔数的遗传力很低,同时又是限性表达性状。但不同品系,窝产仔数的变化范围在2～20头,平均为9～10头;其表型标准差在2．5～3头之间;遗传力在0．1～0．15之间。因此,通过猪育种手段（MAS）提高猪产仔数还有相当大的空间。 相似文献
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与猪窝产数相关联的单个基因或无名遗传标记的识别，对养猪业具有巨大的经济影响。这类遗传标记的识别，对养猪业具有巨大的经济影响，为害遗传多态性可应用于标记辅助选择方案以提高繁殖效率，我们报道了与雌激素体基因多态性有关的、窝产仔数一个主基因之间的差异解释了窝产仔数的显增加－每窝大约多产１．５头猪以及多于１头的活仔猪，结果表明有利基因对生长速度和背膘没有负的基因多效性影响，在标记辅助选择／基因渗入方案中 相似文献
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本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。 相似文献
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魏静 《四川畜牧兽医学院学报》2009,(4):28-32
在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。 相似文献
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以国际标准强毒Ｒ株人工感染非免疫产蛋鸡,定时扑杀,分别从鼻窦、眶下孔、气管、肺、气囊、卵巢和输卵管分离ＭＧ,并收集感染鸡所产蛋分离ＭＧ。结果表明,人工感染４８小时后上、下呼吸道及肺已被全面感染,９６小时气囊已被感染,１２０小时输卵管已能分离到ＭＧ,卵巢始终分离不到ＭＧ。人工感染鸡自１４４小时便能在其所产蛋中分离出ＭＧ。药物治疗能在７２小时内消除感染,油乳剂苗则需２４天后逐渐降低蛋内ＭＧ分离率,药物卵内注射、种蛋药浴、高温处理均能杀死卵内ＭＧ,但以研制的种蛋浸泡剂药浴效果为最好。 相似文献
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Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF
Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo. 相似文献
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乳酸杆菌作为益生菌广泛用于人和动物.本文综述了乳酸杆菌改善宿主健康的机制.乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道.文章重点讨论了乳酸杆菌表面成分(表面蛋白、脂磷壁酸和肽聚糖)与肠道受体(C型凝集素受体、Toll样受体和Nod样受体),阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制. 相似文献
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REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air. 相似文献