日粮赖氨酸水平对皖西白鹅繁殖力的影响

在日粮主要营养成份达标的基础上,通过调节赖氨酸水平0.49%、0.64%、0.79%,探讨其对皖西白鹅繁殖力的影响,结果表明:1赖氨酸水平影响产蛋量P<0.05,而不影响其它的繁殖力指标P>0.05;20.64%的赖氨酸水平最能体现皖西白鹅的繁殖性能。     

Stocking strategies

Abstract  Stocking, transfer and introduction of fish are commonly used to mitigate loss of stocks, enhance recreational or commercial catches, restore fisheries or to create new fisheries. However, many stocking programmes are carried out without definition of objectives or evaluation of the potential or actual success of the exercise. This paper describes a strategic approach to stocking aimed at maximizing the potential benefits. A protocol is discussed which reviews factors such as source of fish, stocking density, age and size of fish at stocking, timing of stocking and mechanism of stocking. The potential genetic, ecological and environmental impacts of stocking are described.     

长江水系中华绒螯蟹线粒体DNA的遗传多样性研究

本文对长江水系南京和江都地区中华绒螯蟹共61个个体的线粒体COI基因进行了限制性片段长度多态性(RFLP)分析。应用PCR技术扩增了中华绒螯蟹线粒体COI基因,选用8种能识别4碱基的限制性内切酶对该基因片段进行RFLP分析。在两个群体中共检测出8种复合单倍型,其中复合单倍型AAAAAAAA和BBBBBAAB为两个群体所共有,它的个体数所占的百分比在两个群体(南京和江都)中分别为87.9%、12.1%和50.0%、25.0%。在南京群体中,复合单倍型间的遗传距离为0.077,而在江都群体中,复合单倍型间的遗传距离为0.004～0.077；南京和江都群体的线粒体COI基因多态度(或称核苷酸多样性指数)π值分别为0.008和0.019。结果说明长江水系中华绒螯蟹具有一定的群体内遗传多样性。     

网箱培育军曹鱼亲鱼及人工育苗研究

12月底从海上网箱挑选14尾1 5龄以上,健康、外表无伤的军曹鱼(Rachycentron cana dum),移至陆地盖有顶棚的大水泥池进行强化培育。经过4个月左右的培养,结果显示,亲鱼在陆地强化培育比在海区网箱提前约7 d成熟并自然产卵。受精卵在室内育苗池进行人工育苗,在海水比重为1. 020±0. 5,pH 8 1~8 4,水温在27. 0、29. 2 ℃时,仔鱼孵出时间分别为26、24 h,孵化率为88 .8%~93 .5%。孵出后的仔鱼在第7~9天为死亡高峰期,第11天左右的仔鱼体色有明显的变化,由棕红色变为黑色。经过1个月的培养,仔鱼的成活率约为9%。     

菲律宾蛤仔土池中间育成的研究

2002~2003年在约80 hm2土池进行了菲律宾蛤仔中间育成试验。试验结果表明,在适时肥水、追肥、清池,水温20~25℃的条件下,放养密度3.0×104~5.0×104枚/m2,放养规格>1.5 mm,平均生长速度>80μm/d,最高可达250μm/d,成活率>80%;不适时肥水、追肥、清池,放养规格又偏小(壳长<0.4 mm)条件下,平均生长速度为26.6μm/d,成活率只有30%。表明放养规格、肥水、追肥、清池及适时疏苗是影响中间育成效果的主要因素。     

应用型本科农学专业作物育种学教学改革探讨

讨论了作物育种学课程改革的意义,介绍作物育种学的改革措施,以达到更好的教学效果。     

2013年隆德县马铃薯脱毒种薯三级繁育体系建设做法及成效

介绍了隆德县马铃薯脱毒种薯三级繁育体系建设主要做法及取得的成效,分析马铃薯脱毒种薯三级繁育体系建设存在的问题,并提出建议,为进一步做大做强马铃薯产业提供依据。     

Breeding programmes for smallholder sheep farming systems: II. Optimization of cooperative village breeding schemes

A simulation study was conducted to optimize a cooperative village‐based sheep breeding scheme for Menz sheep of Ethiopia. Genetic gains and profits were estimated under nine levels of farmers' participation and three scenarios of controlled breeding achieved in the breeding programme, as well as under three cooperative flock sizes, ewe to ram mating ratios and durations of ram use for breeding. Under fully controlled breeding, that is, when there is no gene flow between participating (P) and non‐participating (NP) flocks, profits ranged from Birr 36.9 at 90% of participation to Birr 21.3 at 10% of participation. However, genetic progress was not affected adversely. When there was gene flow from the NP to P flocks, profits declined from Birr 28.6 to Birr ?3.7 as participation declined from 90 to 10%. Under the two‐way gene flow model (i.e. when P and NP flocks are herded mixed in communal grazing areas), NP flocks benefited from the genetic gain achieved in the P flocks, but the benefits declined sharply when participation declined beyond 60%. Our results indicate that a cooperative breeding group can be established with as low as 600 breeding ewes mated at a ratio of 45 ewes to one ram, and the rams being used for breeding for a period of two years. This study showed that farmer cooperation is crucial to effect genetic improvement under smallholder low‐input sheep farming systems.     

Optimizing the use of breed types in developing country livestock production systems: a neglected research area

Developing country livestock production systems are diverse and dynamic, and include those where existing indigenous breeds are currently optimal and likely to remain so, those where non‐indigenous breed types are already in common use, and systems that are changing, such as by intensification, where the introduction of new breed types represents significant opportunities. These include opportunities to improve the livelihood of the world's poor, increase food and nutrition security and enhance environmental sustainability. At present, very little research has focused on this issue, such that significant knowledge gaps in relation to breed‐change interventions remain. The purpose of this study is to raise awareness of this issue and suggests strategic research areas to begin filling these knowledge gaps. Such strategic research would include (i) assessing the impact of differing breed types in developing country livestock productions systems, from a range of viewpoints including intrahousehold livelihood benefit, food and nutrition security at different scales, and environmental sustainability; (ii) identification of specific livestock production systems within developing countries, and the type of livestock keepers within these system, that are most likely to benefit from new breed types; and (iii) identification of new breed types as candidates for in‐situ testing within these systems, such as through the use of spatial analysis to identify similar production environments combined with community acceptance studies. Results of these studies would primarily assist stakeholders in agriculture, including both policy makers and livestock keepers, to make informed decisions on the potential use of new breed types.     

An insight into population structure and gene flow within pure‐bred cats

Investigation of genetic structure on the basis of pedigree information requires indicators adapted to the specific context of the populations studied. On the basis of pedigree‐based estimates of diversity, we analysed genetic diversity, mating practices and gene flow among eight cat populations raised in France, five of them being single breeds and three consisting of breed groups with varieties that may interbreed. When computed on the basis of coancestry rate, effective population sizes ranged from 127 to 1406, while the contribution of founders from other breeds ranged from 0.7 to 16.4%. In the five breeds, F_IS ranged between 0.96 and 1.83%, with this result being related to mating practices such as close inbreeding (on average 5% of individuals being inbred within two generations). Within the three groups of varieties studied, F_IT ranged from 1.59 to 3%, while values were estimated between 0.04 and 0.91%, which was linked to various amounts of gene exchanges between subpopulations at the parental level. The results indicate that cat breeds constitute populations submitted to low selection intensity, contrasting with relatively high individual inbreeding level caused by close inbreeding practices.