种公鸡体形外貌及精液品质性状的聚类分析

本研究对种公鸡的体形外貌及精液品质共14个性状，用统计分析软件SPSS(Ver．11．0)进行了聚类分析，结果表明：在SPSS提供的聚类分析方法中，沃特氏(Ward’s method)聚类分析法把这些性状分为5类，能较全面反映性状实际情况。这一结果为种公鸡的体形外貌、精液品质的选育提供了科学依据。     

杂交中籼新组合特优559的选育与应用

特优５５９系江苏沿海地区农科所用提纯的龙特甫Ａ与盐恢５５９配制育成的杂交中籼新组合。该组合在１９９３～１９９５年江苏省和全国区试中，产量连居第一，１９９６年４月，经江苏省农作物品种审定委员会审定通过。预计“九五”期间在我国杂交中籼稻区有广阔的应用前景     

提型杂种小麦几个主要农艺性状的因子分析

借助于因子分析法,把16个提型杂种小麦的8个主要农艺性状分成受4个独立公因子制约的4个性状群。被确定并命名的4个公因子是:f_1,籽粒生产力因子,它由穗粒数、恢复度、千粒重构成;f_2,营养生长势因子,由穗长、抽穗期、株高构成;f_3、f_4均由一个性状构成,分别叫作小穗数因子和有效穗数因子。受同一个因子制约的性状的全体称之为因子群,文中建议在育种过程中按因子群进行性状选择。试验结果的分析表明,因子分析法是处理多种性状,确定数目较少的起立导作用的因子的一种有用方法,文中介绍了因子分析法的统计学原理和具体计算步骤 。     

国外肉羊遗传育种研究进展

绵羊群体中存在大量的品种内和品种间的遗传变异。这种变异影响羔羊肉及羊肉生产的性状 ,并提供遗传改良肉质性状的潜力。本文综述活体性状的遗传变异 ,包括生产系统和育种目标 ;品种 /基因型评价 ;遗传参数和选择所致的遗传变化评分 ;信息和改良系统的组织等     

Cholinesterase activities in uterus of normal and fenchlorphos treated blue foxes (Alopex lagopus) during various reproductive states

The uterine acetylcholinesterase and total cholinesterase (acetylcholinesterase plus butyrylcholinesterase) activities in normal and fenchlorphos treated blue fox vixens were determined during various reproductive states.AChE and Total-ChE of non-medicated vixens in oestrus were about one half of those in anoestrus. In pregnant uteri (luteal phase) the activities were 25 % and 30% compared to anoestrus.In vixens given 100 mg/kg fenchlorphos for 3 weeks during anoestrus, the remaining activity of AChE in uterus were in average 37%. Pregnant and non-pregnant vixens in the luteal phase medicated prior to mating and during time of implantation, displayed AChE activities which were only moderabely reduced (remaining activities 83% and 72% compared to medicated animals in anoestrus: remaining activity 37%).Plasma ChE-activity increased during pregnancy in the controls while enzyme activity was strongly reduced in animals given 100 mg/kg fenchlorphos daily through the whole pregnancy.It was concluded that the previous reported embryotoxic effect of fenchlorphos in the blue fox did not seem to be directed towards the moderate inhibition of the uterine cholinesterases.     

Kresse (Lepidium sativum L.) als Bioindikator zur Beurteilung der pflanzenphysiologischen Verträglichkeit von Flüssigmist

Uptake and distribution of nitrogen in old and new German summer wheats
Five old German summer wheat varieties, bred in the first third of this century, were compared with five new varieties in an outdoor pot trial. The modern genotypes had taken up slightly more N, both at anthesis and at maturity. At anthesis, N percentage in all organs was considerably higher for modern cultivars. This resulted mainly from a dilution effect caused by superior dry masses of old varieties. Modern genotypes accumulated more N in the upper leaves and ears. As compared with the old varieties, less N was found in the stems of the new cultivars. At maturity, N concentration in vegetative organs was simular for both groups of varieties. N percentage of grains was higher for old cultivars. However, the new genotypes achieved higher N yields. This resulted in part from the slightly higher assimilation of N. Moreover, new genotypes were superior in N translocation which was reflected by higher nitrogen harvest indexes. The postfloral loss of N from the vegetative tissue depended on the organ and the age of the varieties.     

Simulation of the options for a national control programme to eradicate scrapie from Great Britain

Because of the risk to public health posed by the potential presence of bovine spongiform encephalopathy (BSE) in sheep, there are plans to eradicate transmissible spongiform encephalopathies (TSEs) from the British sheep population. We used a mathematical model for the spread of scrapie between sheep flocks to assess the efficacy of five control strategies at eradicating the infection from the national flock. These range from ram-genotyping schemes through whole-flock genotyping with selective culling to whole-flock slaughter. The impact of control was considered under three scenarios for the long-term dynamics of scrapie in GB: two in which scrapie is ultimately eliminated (with different median extinction times) and one in which scrapie remains endemic. Results suggested that it is feasible to eradicate scrapie from the British sheep flock, but that any national control programme will take decades to eliminate the disease and be costly. The most-effective strategy, measured in terms of the probability of eradication and time taken for eradication, was predicted to be whole-flock culling, which was effective under all three scenarios for the long-term dynamics of scrapie. Strategies involving whole-flock genotyping with selective culling were also effective, though they were predicted to take longer to eradicate scrapie than whole-flock culling. Ram-genotyping schemes were effective in some instances, but not for the scenario where scrapie remained endemic in the national flock. At low levels of reporting of clinical disease (<20%) the probability of eradication within 100 years was predicted to be <100% and, consequently, low levels of reporting could compromise the effectiveness of a control programme. Moreover, the predicted time taken to eradicate scrapie would increase markedly if the reporting compliance decreased.     

湖南省杂交棉的研究与应用

湖南杂交棉研究不仅起步早，而且成效显著。现已选育出“湘杂棉１号”、“９３─４”等一批高优势组合。湖南开发应用杂交棉具有“天时、地利、人和”三大优势：丰富的热量资源有利杂种优势充分发挥；以“棉─油”两熟为主的耕作制度，以育苗移栽、肥促化调为中心内容的栽培技术规范有利杂交棉的推广和高产：棉衣对杂交棉的渴求和杂优利用常识又为杂交棉的开发应用提供了群众基础。     

Selection for chip quality and specific gravity of potato clones: possibilities for early generation selection

Summary Ten cultivars contrasting in chip quality were grown in the field and in the glasshouse to evaluate three different methods for chip quality assessment. Specific gravity was also measured. The glasshouse culture simulated growth of seedlings and the field culture represented growth of advanced breeding lines. Differences between cultivars for chip quality and specific gravity could be established in both environments. Although ranking of the cultivars in both environments was not identical, both good and bad genotypes could be identified. It seems that mild selection for specific gravity and chip quality among glasshouse-grown seedlings can be exercised. If tubers of glasshouse-grown plants are too small to slice chips, Reflocheck Glucose test strips offer a satisfactory alternative to frying chips. Crip in UK     

Effects of diseases on reproductive performance in Swedish Red and White dairy cattle

The objectives of this study were to evaluate the effect of diseases on days open (DO), days to first breeding (DFB) and days from first breeding to conception (DFBC) using survival analysis models, and to assess the significance of the sire component and its possible confounding effect. The data consisted of a random sample of 20% of all herds enrolled in Swedish recording system and using 100% artificial insemination with at least 15 Swedish Red and White cows calving in 1991. The follow-up period was from 45 to 145 d after calving. After editing, the data sets had 23,927, 28,197, and 22,089 cows for days open, days to first breeding, and days from first breeding to conception, respectively. The Cox models included parity, calving season, cow milk production and age at first calving as fixed effects, and herd and sire as random effects. Ten disease groups were considered as possible risk factors for the reproductive traits. Disease groups were treated differently if they occurred before or after 45 d postpartum. Diseases occurring in the first 45 d after calving were treated as time-independent covariates and diseases occurring after day 45 were treated as time-dependent covariates for days open and days to first breeding. The percentages of censored cows were 35% for days open, 19% for days to first breeding, and 33% for days from first breeding to conception. Days open increased in cows with dystocia, stillbirth, retained placenta, metritis, or other diseases occurring in the first 45 d after calving, and in cows with metritis, mastitis, or other diseases occurring after 45 d. Days to first breeding increased in cows with stillbirth, retained placenta, milk fever, mastitis, foot and leg problems, or other diseases occurring before day 45, and in cows with metritis, mastitis, foot and leg problems, or other diseases occurring after 45 d. Days to first breeding decreased in cows treated for ovulatory dysfunctions either before or after 45 d. Days from first breeding to conception increased in cows with dystocia, stillbirth, retained placenta, metritis, or ovulatory dysfunctions occurring before first breeding, and in cows with mastitis occurring after first breeding. Although the additive genetic components were significant for all traits considered, the sires did not act as confounders because only a small amount of variability for the traits considered in this study was explained by the sires, with estimated heritabilities of 2% on the logarithmic scale and from 3 to 4% on the real scale.