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71.
从2003年以来青海省大通种牛场开始了较大面积的推广工作,到今年己有10年的推广历史了。对一个新品种大面积推广10年是一个极为重要的时间节点。2005年农业部批准"大通牦牛"为新品种并决定颁发新品种证书。截止2013年前己向青海省6州1地1市39个县累计推广大通牦牛种公牛14 640余头,据2013年不完全统计,大通牦牛后裔在省内推广区达91万头以上。今后必需加快品系繁育提高大通牦牛整体水平;加强核心育种群管理确保种牛质量;加强种公牛的动态溯源管理;组识种牛场技术人员深入推广区,传授良种良养的配套技术和野外冷配技术。 相似文献
72.
Eva DE LA PE
A Jos MARTÍN Isabel BARJA Raúl PREZ‐CABALLERO Isabel ACOSTA Juan CARRANZA 《Integrative zoology》2020,15(4):262-275
Testosterone secretion may regulate the reproductive effort and the development of sexual traits, but it may also involve costs at the immunological and metabolic levels. However, the evidence for this trade‐off in wild populations is scarce. Cortisol also plays an important role in mediating the reproductive and immune functions. In this study, we analyzed whether the endoparasite burden relates to hormonal levels (fecal testosterone and cortisol metabolites) and/or morphological sexual traits (size of the dark ventral patch, a trait that indicates reproductive effort in males) in male Iberian red deer. For this purpose, we sampled male red deer harvested during hunting actions in 2 types of populations in south western Spain that differed in structure, affecting the level of male–male competition for mates. We used coprological analyses to estimate the parasite burden mainly of gastrointestinal and bronchopulmonary nematodes and of protozoa, and assessed testosterone and cortisol metabolite levels from fecal pellets. We found a positive relationship of host parasitation with both testosterone levels and the size of the dark ventral patch, but these relationships depended on the intensity of male–male competition in the population, being only found under the high‐competition scenario. These results are discussed under the hypothesis of the testosterone immunocompetence handicap, suggesting a cost at the immunological level, and, therefore, higher susceptibility to parasite infection in males that make a greater reproductive effort. However, this effect seems to be modulated by the social environment (male–male competition) that might lead to different optima in testosterone production and sexual trait development. 相似文献
73.
J Veverka P Thomas A Harch B Clark JF Bell B Carcich J Joseph C Chapman W Merline M Robinson M Malin LA McFadden S Murchie SE Hawkins R Farquhar N Izenberg A Cheng 《Science (New York, N.Y.)》1997,278(5346):2109-2114
On 27 June 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1212 kilometers of asteroid 253 Mathilde. Mathilde is an irregular, heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers. The asteroid's surface is dark (estimated albedo between 0.035 and 0.050) and similar in color to some CM carbonaceous chondrites. No albedo or color variations were detected. The volume derived from the images and the mass from Doppler tracking of the spacecraft yield a mean density of 1.3 +/- 0.2 grams per cubic centimeter, about half that of CM chondrites, indicating a porous interior structure. 相似文献
74.
野生龙葵果中营养成分的研究 总被引:13,自引:0,他引:13
本研究对野生龙葵果营养成分进行了比较全面地分析测试,对矿物质及维生素含量进行分析的基础上,对野生龙葵果的其它营养成分进行了分析,并与一些常用果蔬进行了对比研究。结果表明,野生龙葵果含有丰富的营养成分。 相似文献
75.
云南农业大学信息服务与用户调查研究分析 总被引:4,自引:0,他引:4
通过对云南农业大学的教师、研究生和本科生的信息需求调查,了解到各类用户利用文献信息的状况和对文献信息的需求,为图书馆开展信息服务提供了依据。 相似文献
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78.
The role that the environment plays in vector-borne parasite infection is one of the central factors for understanding disease dynamics. We assessed how Neotropical bird foraging strata and habitat preferences determine infection by parasites of the genera Haemoproteus, Plasmodium, Leucocytozoon, and Trypanosoma and filarioids, and tested for phylogenetic signal in these host–parasite associations. We performed extensive searches of the scientific literature and created a database of hemoparasite surveys. We collected data on host body mass, foraging strata, habitat preference, and migratory status, and tested if host ecological traits predict each hemoparasite occurrence and prevalence using a phylogenetic Bayesian framework. Species of Plasmodium tend to infect birds from tropical forests while birds from altitudinal environments are likely to be infected by species of Leucocytozoon. The probability of a bird being infected by filarioid or Trypanosoma is higher in lowland forests. Bird species that occur in anthropic environments and dry habitats of tropical latitudes are more susceptible to infection by species of Haemoproteus. Host foraging strata is also influential and bird species that forage in the mid-high and canopy strata are more prone to infection by species of Haemoproteus and filarioids. We also identified phylogenetic signal for host–parasite associations with the probability of infection of Neotropical birds by any hemoparasite being more similar among more closely related species. We provided a useful framework to identify environments that correlate with hemoparasite infection, which is also helpful for detecting areas with potential suitability for hemoparasite infection due to land conversion and climate change. 相似文献
79.
为探究低磷胁迫下小麦根系生理和形态的变化及其对镉的吸收能力的影响,以Ca3(PO4)2作为磷源,通过砂培试验研究了在低磷胁迫下小麦根系形态和分泌物变化特征,以及这些变化对难溶态镉(CdCO3)的活化与吸收的影响。结果表明,在低磷处理中,小麦地下部生物量显著低于对照,降幅为27.3%(P<0.05),根长度、根表面积和根体积均显著变小(P<0.05)。此外,低磷胁迫下小麦地上部和地下部磷含量均显著降低,降幅分别为35.4%和23.1%(P<0.05),但是显著促进了难溶态磷的溶解(P<0.05)。同时还发现低磷胁迫显著提高了小麦植株Cd含量和Cd的总活化量,增幅分别为190.8%和82.8%(P<0.05)。低磷胁迫下培养基pH降低了0.3,同时根中草酸根和苹果酸根含量显著升高,增幅分别为1 588.1%和37.7%(P<0.05),由此可见,低磷胁迫下小麦通过分泌质子和羧酸根促进了磷的活化,并促进了Cd的活化,进而导致小麦Cd吸收的增加。这些结果阐明了低磷胁迫影响小麦Cd吸收的机制。 相似文献
80.
西藏不同青稞品种的品质差异分析 总被引:2,自引:0,他引:2
为了解西藏地区不同青稞品种的品质差异,采集了西藏青稞主产区的不同青稞品种,并对青稞中的水分、淀粉、粗蛋白、粗纤维、矿质元素以及有效成分总黄酮、花青素、β-葡聚糖等14项指标进行了检测。结果表明:有色青稞中淀粉和微量元素Mn、Cu、Zn的含量在年度间存在着显著的差异,且有色青稞微量元素含量普遍偏低;青稞总黄酮含量范围在0.14%~0.42%,均值为0.23%;β-葡聚糖含量范围为2.65%~6.52%,均值为4.59%;有色青稞花青素含量变化较大,范围在0.022 7~0.649 7 mg/g,均值为0.133 2 mg/g。总黄酮含量、β-葡聚糖含量年际间差异不大,花青素含量年际间差异巨大。总黄酮含量有色青稞显著高于普通青稞,而β-葡聚糖含量二者无显著差异。 相似文献