动物养殖业所面临的挑战和机会(续)     

Jon Ratcliff 《饲料广角》2001,(17):23-24

内部的挑战和机遇 生产和均一性 挖掘遗传的潜力,也就是繁殖性能或生长的潜力,对于动物养殖业来说是一个连续的挑战。营养通常不是限制的因素。然而,营养学家和养殖者承担这一挑战。为了最大程度地发挥动物的生产性能的潜力,高精确度的分析技术,包括DNA排列顺序,使我们能够充分了解和分析胃肠  相似文献   

棉花混选-混交育种体系遗传改良效应研究——Ⅰ.主要育种目标性状的响应     

马家璋  颜清上 《棉花学报》1993,(1)

研究了陆地棉主要性状对混选—混交育种体系的响应。两轮群体提高了产量、早熟性和降低了麦克隆值的平均数;扩大了纤维品质的变幅;增加了高产株率,但对改进抗枯黄萎病性不明显。一轮群体的效果低于二轮。两次混交扩大了产量和纤维品质的变幅,增加了正末端的个体频率。一次混交的作用不及两次。早代混选相对缩小了群体变幅。一次混交后再经两代开放授粉和对一轮群体再混选,均表现出有益的反响。  相似文献   

动物养殖业所面临的挑战和机会（续）     

Jon Ratcliff 《饲料广角》2001,(18):24-25

(上接第17期) 霉菌毒素的污染 饲料原料和垫草受到霉菌毒素污染的现象在亚太地区是广泛存在的(Leeson等,1995).亚太的大部分地区属于高温湿热的气候,这给霉菌的生长与繁殖以及产生霉菌毒素提供了有利的条件.由于全球极端的气候条件以及饲料原料的进口,通常没有霉菌毒素问题的国家,如澳大利亚,现在也不得不考虑预防霉菌毒素的问题.人们常常误解:"霉菌毒素是一个季节性的问题".  相似文献   

Concerning the Future of the NSF     

Cotton FA 《Science (New York, N.Y.)》1992,258(5081):379

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Movement patterns of seaward migrating European eel (Anguilla anguilla) at a complex of riverine barriers: implications for conservation          下载免费PDF全文

Adam T. Piper  Jon C. Svendsen  Rosalind M. Wright  Paul S. Kemp 《Ecology of Freshwater Fish》2017,26(1):87-98

River infrastructure such as weirs and hydropower stations commonly present migrating fish with multiple potential passage routes. Knowledge of the cues fish use to navigate such environments is required to protect migrants from hazardous areas and guide them towards safe passage; however, this is currently lacking for many species. Employing high‐resolution positioning telemetry, this study examined movements of downstream migrating adult European eel, Anguilla anguilla, as they encountered a complex of water control structures in one location on the River Stour, southern England. The distribution of eels across five potential routes of passage differed from that predicted based on proportion of discharge alone. Certain routes were consistently avoided, even when the majority of flow passed through them. Passage distribution was partially explained by avoidance in the vicinity of a floating debris boom. Movement paths were nonrandomly distributed across the forebay and eels moved predominantly within a zone 2–4 m from the channel walls. Understanding of avoidance and structure oriented movementation exhibited by eels will help advance effective guidance and downstream passage solutions for adults.  相似文献   

高产棉花太阳辐射能利用率及干物质分配规律研究   总被引：6，自引：0，他引：6  

潘学标  邓绍华  蒋国柱  吴同礼  董占山  崔秀稳  潘晓康  龙腾芳 《棉花学报》1992,(Z1)

通过对1988～1989年高产棉花栽培试验结果进行分析发现,棉花的太阳辐射利用率在叶面积系数小于2.0时随叶面积系数的增加而线性增加,大于2.0时增加变缓。从生育时间看,7月中旬前太阳辐射利用率指数上升,7月中旬至8月底相对稳定在1.2～1.4克/兆焦左右,9月以后又不同程度线性下降。生长季内子棉太阳辐射经济效率1988和1989年分别为0.14和0.15克/兆焦。收获指数与最大叶面积系数呈显著负相关;盛花期之前棉株各器官之间的同伸关系或明显,盛花期后器官的生长相互间无明显的确定性关系。如能调节密度与叶面积系数的关系,使得既提高5～6月的辐射能利用率,同时使7～8月叶面积系数维持在3.0～3.5的适宜范围内,9～10月群体又不早衰,则有利于获得高产。  相似文献   

Effect of maternal cells transferred with colostrum on cellular responses to pathogen antigens in neonatal calves     

Donovan DC  Reber AJ  Gabbard JD  Aceves-Avila M  Galland KL  Holbert KA  Ely LO  Hurley DJ 《American journal of veterinary research》2007,68(7):778-782

OBJECTIVE: To assess the effect of maternal cells or cellular components on neonatal immune responses to intracellular pathogens in calves. ANIMALS: 15 Holstein calves. PROCEDURES: Calves were fed whole colostrum, frozen colostrum, or cell-free colostrum within 4 hours after birth. Leukocytes were obtained from calves before feeding colostrum and 1, 2, 7, 14, 21, and 28 days after ingestion. Proliferative responses against bovine viral diarrhea virus (BVDV) and mycobacterial purified protein derivatives were evaluated. Dams received a vaccine containing inactivated BVDV, but were not vaccinated against mycobacterial antigens. RESULTS: All calves had essentially no IgG in circulation at birth, but comparable and substantial concentrations by day 1. Calves that received whole colostrum had enhanced responses to BVDV antigen 1 and 2 days after ingestion of colostrum. In contrast, calves that received frozen colostrum or cell-free colostrum did not respond to BVDV. No differences were identified among the 3 groups in response to mycobacterial antigens. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that transfer of live maternal cells from colostrum to neonatal calves enhanced responses to antigens against which the dams had previously responded (BVDV), but not to antigens to which the dams were na?ve (mycobacterial purified protein derivatives). Results suggested that cell-mediated immune transfer to neonates can be enhanced by maternal vaccination.  相似文献   

Efficacy of topical eprinomectin in the treatment of Chorioptes sp. infestation in alpacas and llamas     

Plant JD  Kutzler MA  Cebra CK 《Veterinary dermatology》2007,18(1):59-62

Chorioptes sp. mite infestation is increasingly recognized as a cause of skin disease in New World camelids and there is a need for an effective treatment protocol to eliminate herd infestation. In this field trial, eprinomectin applied topically at the rate of 0.5 mg kg(-1) weekly for 10 weeks was found to be ineffective in a herd of 12 llamas and 16 alpacas.  相似文献   

Thoracolumbar myelopathies in pug dogs     

Ian J. Wachowiak  Jon S. Patterson  Kathryn M. Winger  Kathleen L. Smiler  Robert Cole  Rachel Moon  Michael Kluz  Lisa R. Bartner 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2023,37(2):618-625

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棉花分子育种研究进展     

陈秀兰  张玉忠  张军 《棉花学报》1997,(1)

本文主要综述了我国近２０年来棉花分子育种在理论基础、技术方法、育种机理以及新品种培育等方面研究取得的成就及新进展，并讨论了棉花分子育种的发展方向  相似文献