家蚕母种继代蛾区选择方法对种性维持的影响

为了有效保持生产实用家蚕品种的优良性状,在家蚕母种继代繁育中采用5种选择方法选择继代蛾区,探讨种性维持效果。分析8年12代及F1代的成绩表明:所有性状以保持种性为主,采用选留平均数上下1个标准差范围内蛾区的稳定化选择和以茧丝质指标在平均数-0.5~1.0标准差范围内选择,并结合健康性指标选留高值的综合选择,有利于家蚕母种的种性维持。     

选择产蛋量七个世代蛋壳及蛋品质的相关反应

以北京白鸡Ⅲ系七世代选择群和基础群为材料,估计选择产蛋量七个世代对蛋壳及蛋品质产生的相关反应.结果表明,经七个世代选择,产蛋量、蛋重、蛋白高度和哈夫单位都有所提高,而蛋壳厚度和蛋比重有一定程度下降.估计蛋壳厚度、蛋白高度和哈夫单位的遗传力分别是0.159 5、0.017 8和0.099 4.产蛋量与蛋白高度、哈夫单位和蛋壳厚度呈负遗传相关.选择产蛋量使蛋壳品质发生负向相关反应.     

The role of genetic engineering in livestock production

In this paper we discuss the use of genetic engineering in livestock production. We examine the main two different aspects of genetic engineering: cloning and transgenesis. After commenting what has been expected from both techniques in livestock production in the last 25 years, the practical difficulties for implementing cloning and transgenesis are examined. Apart from technical difficulties, problems derived from the detection of genetically superior animals and evaluation of the clones and the transgenic animals make these techniques less interesting than they appear to be. Most of the observed variability of the economically interesting traits is not genetic, genetic evaluation needs a large number of animals and cloning success will represent a serious loss of genetic variability and the loss of the flexibility needed for markets in constant evolution. There is a risk in transgenic animals of production of new intermediate biochemical products that may be toxic, allergenic or carcinogenic. The benefits produced by transgenic animals hitherto hardly justify this risk. The expectations that genetic engineering produced 25 years ago should be re-examined, considering the risks and the high investment required.     

Foraging behavior of heifers with or without social models in an unfamiliar site containing high plant diversity

Grazing behavior, diet selection and weight gain of heifers (with or without social models) were assessed in an unfamiliar site containing high plant diversity. The study was performed within a tropical forest ecosystem containing a mixture of grass forb/herb, shrub and tree species. Ten inexperienced crossbred Bos taurus × Bos indicus heifers (7 ± 1 months old) were randomly assigned to one of two groups: naive or naive + social model (sm) and two experienced heifers (16 months old) were assigned to the second group. Naive heifers were bottle-nursed from days 2 to 90 after birth and began grazing at 1 month of age in tropical grass monocultures, while experienced animals had been foraging in sites containing a high diversity of plant species for 3 months prior to the study. Each group grazed in separate paddocks for a 12-week period during the rainy season, and animals were observed using focal sampling from 7:00 to 19:30 h to assess diet composition based on bite counts. Weight gain was assessed every 14 days. Paddocks contained from 1481 to 1789 kg/ha of herbaceous dry matter, enough to support the heifers throughout the study without affecting diet selection. Shrub and tree cover ranged from 55.2 to 58.4% across treatments. Bites per minute were adjusted to a log-scaled quadratic-plateau model and the curves showed no differences between treatments (P = 0.756). However, diet composition differed between groups (P < 0.001), with naive + sm heifers ingesting a greater proportion of trees (P < 0.001) and shrubs (P = 0.02), while naive heifers ingested more forb/herbs (P = 0.02); no difference in grass consumption was observed (P = 0.92). Heifers in both treatments consumed the same plant species (50 from 26 families). Over time, utilization of several plant species increased or decreased (P < 0.05), eventually leveling off for the remainder of the study. Although differences in diet composition were observed, they did not affect overall weight gain (117 and 113 g/day in the naive and naive + sm groups, respectively; P = 0.913). However, initial post-weaning weight loss was avoided in the naive + sm group. Social learning facilitates a higher use of shrubs and trees in tropical pastures containing a high diversity of plant species with different growth habits. As many plant species have high potential as forage, more effort should be placed on developing mechanisms to increase their dietary inclusion by cattle.     

湖北五峰后河国家级自然保护区果子狸秋冬季栖息地选择

2006年6月～2007年3月,在湖北五峰后河国家级自然保护区内,应用选择系数、选择指数、判别分析,对果子狸在秋冬季节栖息地的选择和利用进行了初步研究。研究结果表明,秋季与冬季果子狸对栖息地的选择有差异性。秋季在低海拔地区有较多林木果实、藤本果实成熟,不需要消耗太多能量即可满足自身需要。冬季气温下降,果子狸较喜欢选择海拔较高的阳坡活动,以获取更多热量。     

贵阳市高尔夫俱乐部草坪基地建植与管理

通过贵阳市高尔夫球场草皮基地的建植和养护管理 ,从中总结了过渡气候带建植草坪应注意的一些问题。根据所建草坪的功能 ,选择相适应的草种应用于高尔夫球场。并对其适应性进行了研究     

优选高校教材的探讨

教材选用是高校教材建设的一项基础性工作，是提高教学质量的关键。本文结合高校教材选用工作的实践，探讨如何提高教材选用质量。     

Adaptive evolutionary expansion of the ribonuclease 6 in Rodentia

Ribonuclease 6 (RNase6 or RNase K6) is a protein that belongs to a superfamily thought to be the sole verte‐brate‐specific enzyme known for a wide range of physiological functions, including digestion, cytotoxicity, angiogenesis, male reproduction and host defense. In our study, 51 functional genes and 11 pseudogenes were identified from 27 Rodentia species. Intriguingly, in the 3 main lineages of rodents there were multiple RNase6s identified in all species of Ctenohystrica, whereas only a single RNase6 was observed in other Rodentia species examined except for 2 species in the mouse‐related clade. The evolutionary scenario of “birth (gene duplication) and death (gene deactivation)” and gene sorting have been demonstrated in Ctenohystrica. In addition, bursts of positive selection, diversification of isoelectric point and positive net charge have been identified in Ctenohystrica, especially at two key sites that are involved in antimicrobial function. Site Trp30 has undergone positive selection and Ile45 has changed into other residues in Group B and Group C of the Ctenohystrica. Our results demonstrated a complex and intriguing evolutionary pattern of rodent RNase6, and indicated that functional modification may have occurred, which establishes an important theoretical foundation for future functional assays in rodent RNase6.     

群体遗传惯性理论与选择极限 续

2 群体遗传惯性与选择极限的理论分析根据群体遗传惯性理论,我们可以把外部力量(主要是选择)对群体的作用力称为选择压(Se-lection Pression,Sp),由这种选择压的作用而引起群体期望能获得的遗传反应称为期望选择反应(Expected Selection Respones,ER),或者简称选择反应(Selection Respones,R)。而把群体实际所获得的遗传值的变化定义为遗传增量(GeneticGain,△G),或称为获得遗传反应(Observed Se-lection Respones,OR)。这样我们就把群体的实际遗传增量定义为选择反应与群体遗传惯性力之差,即:     

浅谈奶牛肢蹄的测量评定与日常养护

本文简要地介绍了奶牛肢蹄的重要性,肢蹄性状的测量评定与选择,及其日常养护措施。