家蚕基因组研究重要成果——40种蚕类基因组重测序及遗传变异图

2009年8月27日，国际著名学术杂志《Science））（（〈科学》）在线发表了西南大学主持完成的重要科研成果——《40个基因组完全重测序揭示蚕的驯化事件及其相关基因》（《Complete reseanquencing of 40 genomes reveals domestication events and genes in silkworm（Bombyx）》）2004年发表世界第一张家蚕基因组框架图后，中国科学家再次在《Science））杂志上。     

樊净山自然保护区黔金丝猴生境选择的研究

适宜的生境是珍稀濒危生物生存的决定性条件,对珍稀濒危生物生境的系统研究是生物多样性保护的前提。金丝猴是中国特有并且珍稀的濒危物种,黔金丝猴又是三种金丝猴中分布最为狭窄、对生境要求最为苛刻的一种。本文从黔金丝猴的最佳适宜生境、适宜生境和较适宜生境三个生境选择方面对生境内植物群落特征、环境因子、极端环境因子等进行了系统分析,对黔金丝猴的季节活动规律、活动区域和食物特点进行了系统的研究。结果表明常绿针阔混交林是黔金丝猴的最佳生存的植被群落,其最适宜的年均温度为8～15C,极端最低温度为-2.5C,极端最高温度为25C,最适宜生存的海拔高度为1500～1700m。在同一区域,植物多样性越多,越适宜黔金丝猴的生存。温度和食物是决定黔金丝猴种群活动范围大小的主要生境因子,海拔高度、植被群落特征、温度是黔金丝猴对生境选择的主要限制因子。图3表3参16。     

美国国有林管理体制对我国国有林区改革的启示

培训考察团先后访问了美国联邦国有林管理局、美国南部林区(第八区)国有林管理分局、西南林区(第五区)安吉斯林管区和乔治亚州农业厅以及私有林主。美国森林资源丰富,国有林垂直管理体制简单高效,森林经营科学规范。比较了中美两国国有林管理方面的主要差异,分析了我国重点国有林区管理体制存在的问题,以期为我国国有林管理体制改革提供借鉴。     

Variability in mixing efficiency and laboratory analyses of a common diet mixed at 25 experiment stations

An experiment involving 25 experiment stations in the North Central and Southern regions (NCR-42 and S-288, respectively) was conducted to assess the degree of uniformity of diet mixing among stations and to assess the variability among station laboratories in chemical analysis of mixed diets. A fortified corn-soybean meal diet was mixed at each station using a common diet formula (except for vitamin and trace-mineral additions). The diet was calculated to contain 14% crude protein (CP), 0.65% Ca, 0.50% P, and 125 ppm Zn (based on 100 ppm added Zn). After mixing, samples were collected from the initial 5% of feed discharged from the mixer, after 25, 50, and 75% was discharged, and from the final 5% of discharged feed. The five samples were sent to the University of Kentucky, finely ground, and divided into subsamples. Each set of five subsamples from each station was distributed to three randomly selected stations for analysis of CP, Ca, P, and Zn (i.e., each station analyzed five diet sub-samples from three other stations). In addition, two commercial and two station laboratories analyzed composites of the five subsamples from each of the 25 mixed diets. Based on the laboratories that analyzed all diets, means were 13.5, 0.65, and 0.52%, and 115 ppm for CP, Ca, P, and Zn, respectively. Ranges of 11.8 to 14.6% CP, 0.52 to 0.85% Ca, 0.47 to 0.58% P, and 71 to 182 ppm of Zn were found among the 25 diet mixes. The coefficients of variation among the 25 diet samples for CP, Ca, P, and Zn were 4.3, 9.3, 4.1, and 17.4%, and among the 25 laboratories were 3.6, 12.5, 10.7, and 11.1%, respectively. Overall analyses of the five sub samples were, respectively, CP: 13.4, 13.6, 13.4, 13.5, and 13.4% (P < 0.06); Ca: 0.66, 0.67, 0.67, 0.66, and 0.67%; P: 0.50,0.51,0.51,0.50, and 0.50%; and Zn: 115, 116, 112, 113, and 120 ppm (P < 0.001). Diets were not uniformly mixed at all stations (station x sample No. was P < 0.08 for Ca and P < 0.01 for CP, P, and Zn). Among stations, the range of the five samples, expressed as a percentage of the mean and averaged for CP, Ca, P, and Zn, varied from +/- 1.1% (i.e., 98.9 to 101.0%) to +/- 12.9% (84.6 to 110.4%), with an overall average of +/- 5.2%. Neither type nor volume of mixers was related to mixing uniformity. The results suggest that uniformity of diet mixes varies among experiment stations, that some stations miss their targeted levels of nutrients (especially Zn), and that the variability among experiment station laboratories in analysis of dietary Ca, P, and Zn in mixed diets is quite large.     

Comparison of dietary selenium fed to grower-finisher pigs from various regions of the United States on resulting tissue Se and loin mineral concentrations

A study was conducted to evaluate the mineral content of pork tissue with particular emphasis on Se between various states (regions) having different diet (grain) indigenous Se concentrations. The study involved 19 states in the north, central, and southern regions of the United States, with committee members of NCR-42 and S-1012 (formerly S-288). A total of 62 pigs were used, with collaborators sending 100-g samples each of loin, heart, and liver, and a 3- to 4-g sample of hair (collected along the topline) from two to five market-weight pigs to a common laboratory for analysis. Diets at each station were formulated with locally purchased soybean meal and grain that was either grown or normally fed to pigs within their state. Tissues were analyzed for Se, but only the loin was analyzed for the macro- and micromineral elements. Correlation of dietary minerals to the tissue element was determined. The results demonstrated differences in tissue Se among states (P < 0.01), with high correlations of dietary Se to loin (r = 0.84; P < 0.01), heart (r = 0.84; P < 0.01), liver (r = 0.83; P < 0.01), and hair Se (r = 0.90; P < 0.01) concentrations. The correlation of hair Se to the Se concentration of loin, heart, and liver tissues was high (r > 0.90; P < 0.01). States in the west-central region of the United States and west of the Mississippi river had higher dietary Se and tissue Se concentrations than states in the eastern section of the Corn Belt, east of the Mississippi river, and along the East Coast. Generally, states did not differ greatly in their loin macro- and micromineral concentrations. The simple correlation of dietary minerals to their corresponding loin mineral concentration was generally non-significant, but most macrominerals had decreasing mineral concentrations when the dietary mineral level was higher. These results indicate that regional differences in tissue Se were influenced more by the indigenous Se content of the diet (grain) fed to the pigs than from sodium selenite.     

珍稀濒危树种珙桐的生存特性

珙桐(Davidiainvolucrate)为中国一级保护植物,系第三纪古热带植物的孑遗树种,属于珍稀濒危的单属单种植物。近年来,由于区域开发项目的增多,致使这种古老而珍稀树种的天然分布生境和天然种群数量急剧下降。为此,本文通过大面积的野外调查和查阅资料,研究了珙桐的生物和生态特性,系统分析了珙桐在不同地质阶段的地理分布状况,探讨了促使其种群数量动态变化的主要原因。不同年份标准样地调查表明,在没有人类干扰的区域,珙桐种群数量随年份增加;但是在有人类干扰的区域,珙桐种群数量随年份减少;随着人口密度和人类活动的增加,珙桐种群数量呈对数曲线y=-100.7ln(x)+178.09的速度下降,这表明珙桐种群已由优势种群衰退到濒临灭绝的程度。基于对珙桐的现有研究,提出了珙桐的保护措施。图3参31。     

Towards sustainable intensification of apple production in China—Yield gaps and nutrient use effi ciency in apple farming systems

China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits.However,the annual productivity of China’s apple is significantly lower than that of other dominant apple producing countries.In addition,apple production is based on excessive application of chemical fertilizers and the nutrient use efficiency(especially nitrogen)is therefore low and the nutrient emissions to the environment are high.Apple production in China is considerably contributes to farmers’incomes and is important as export product.There is an urgent need to enhance apple productivity and improve nutrient use efficiencies in intensive apple production systems in the country.These can be attained by improved understanding of production potential,yield gaps,nutrient use and best management in apple orchards.To the end,priorities in research on apple production systems and required political support are described which may lead to more sustainable and environmental-friendly intensification of apple production in China.     

石漠化区地埂桑根系分布特征及其与土壤养分的关系

在重庆黔江石漠化区,选择飞播天然林为对照,以不同管理措施的地埂桑梯田为研究对象,分析了地埂桑根系在田面的水平分布特征及其与土壤养分水平分布之间的定量关系,以客观评价3种梯田管理措施对地埂植物根系分布的影响,并揭示地埂桑的水土保持效应形成机制.结果表明:地埂桑田土壤根系表面积、根系体积及根系质量都显著低于天然林,但天然林土壤根系总长度显著低于清草地.清草地根系表面积和总长度显著高于农耕地和自然生草地;清草地土壤根系总长度、根系表面积、根系体积及根系重量离标准株距离的增大而呈下降趋势.地埂桑田的土壤全磷、全钾、全氮及速效磷含量均显著高于天然林,而有机质含量显著低于天然林.整体上,离标准株的距离对耕地土壤养分含量的影响较小.3种管理措施中,清草地相对能较好的促进桑树根系合理分布,有利于发挥地埂桑的水土保持效应.     

In vivo prediction of internal fat weight in Scottish Blackface lambs, using computer tomography

From a calibration trial involving computer tomography (CT) scanning and dissection of 45 lambs, a prediction equation was derived to estimate total internal fat weight in Scottish Blackface lambs from measurements taken on cross‐sectional CT images. Using data from two cross‐sectional images (at the hip and loin) internal fat can be predicted with relatively high accuracy (adjusted R² = 62.2%, r = 0.79). The derived equation was then used to predict internal fat weights in a further 427 Scottish Blackface lambs from a separate trial. Phenotypic correlations were calculated between predicted internal fat weight and weights of total carcass fat, muscle and bone, predicted using previously derived equations. When considering absolute tissue weights, adjusted for fixed effects, internal fat showed the strongest positive correlation with carcass fat (0.58), followed by muscle (0.36), and then by bone (0.32). When tissue weights were adjusted for fixed effects and total carcass weight (so considering tissue weights relative to size), internal fat showed a lower correlation with carcass fat weight (0.36) and negative correlations with muscle (?0.35) and bone (?0.19). These results provide the basis for more complex studies of relationships (phenotypic and genetic) between internal fat in hill lambs and economically important traits, such as carcass composition and survival of lambs, and tissue levels in different depots in hill ewes.     

家禽饮水系统水压调节器的功能

<正>我们经常与家禽生产者讨论有关家禽饮水的问题,其中有一点已经很清楚:很多家禽生产者不懂得如何使封闭型乳头式饮水系统真正发挥其作用。本文我们将探讨在此饮水系统中如何使用水压调节器(图1)以及它会对饮水系统中的水位和水压产生怎样的作用。