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21.
BC Li W Li H Chen YN Zhang ZT Zhang XY Wang B Gao TC Dou KH Wang 《Reproduction in domestic animals》2013,48(3):368-372
This study was conducted to explore the influencing factors of ova in vitro fertilization (IVF) and transfer of the fertilized ova into the oviduct of recipient hens. The efficiency of fertilization was compared using three aspects: (i) the different time of ova collection and transfer, (ii) egg‐laying period of recipient hen; and (iii) semen volume. The following results are observed: 72%, 40% and 0% of ova were found in ovarian sac in 30～40 min, 50～60 min and more than 90 min post‐oviposition, respectively; 20%, 18%, 14% and 5.8% of ova were fertilized with 0.1, 0.2, 0.5 and 1.0 ml semen, respectively; and 33% and 100% of healthy chickens were hatched from fertile ova with 0.1 and 0.5 ml of semen, respectively. All oocytes obtained from ovary and mid‐oviduct were unfertilized. Embryos were transferred into recipient hens 30 min ± 10 min post‐oviposition, and 70% of shelled eggs were produced. There were no eggs produced in the other transfer times. This demonstrated that live chicken can be obtained by IVF of ova collected shortly after oviposition. It was important that the ovum was transferred into the oviduct infundibulum of recipient hens immediately or shortly after oviposition. 相似文献
22.
Two prenylated isoflavanones (1) and (2) were isolated from the stem bark of Lespedeza bicolor along with the known compounds ethyl caffeate, caffeic acid, protocatechuic acid, betulinic acid, betulin, beta-sitosterol and from the stem heartwood daidzein and isoliquiritigenin. 相似文献
23.
TC Green 《New Zealand veterinary journal》2013,61(6):263-271
Abstract Ideas within the animal welfare science arena have evolved continuously throughout the last 30 years, and will continue to do so. This paper outlines some of these developments. These included reformulation of the five freedoms concept into the five domains of potential welfare compromise. This accommodated weaknesses in the former by distinguishing between the physical/functional and the mental factors that contribute to an animal's welfare state. This development reflected a rising scientific acceptance that the mental experiences of animals were legitimate foci for study and highlighted that what the animal itself experiences represents its welfare status. Initially, most concepts of animal welfare emphasised predominantly negative subjective experiences, such as thirst, hunger and pain, and negative affective states or feelings including anxiety, fear and boredom, but today positive experiences or emotions such as satiety, vitality, reward, contentment, curiosity and playfulness are also considered to be important. During the same period, the focus shifted from evaluating the impacts of individual mental subjective experiences or emotions towards seeking a more comprehensive, multifactorial understanding. The five domains concept was specifically designed to achieve this. Subsequent notions about quality of life (QoL) had the same objective, and emphasised the importance of positive experiences. However, some approaches to QoL assessment relied heavily on empathetic speculation about what animals may experience subjectively and this raised concerns about inappropriate anthropomorphic projections. Such pitfalls may be minimised when informed personnel rigorously apply objectively based methodologies to QoL assessments limited to a short time frame. It is clear that both formal and somewhat less formal QoL assessments of this type are already used to guide decision-making about the ongoing care and therapeutic management of animals on a daily basis. However, application of the recently introduced concepts of ‘a life not worth living’, ‘a life worth avoiding’, ‘a life worth living’ and ‘a good life’ is problematical, because extending the assessment time scale to the whole of life is attended by a number of as yet unresolved difficulties. Accordingly, their value in the practical management of animals is limited so that, at present, reliance on the minimum standards and recommendations for best practice outlined in codes of practice or welfare will continue to be necessary and worthwhile. Nevertheless, these concepts have value in providing a contextual theme that strongly focuses attention on the promotion of a lifelong QoL with an overall balance that is positive. 相似文献
24.
Comparison of the photosynthetic capacity of Siberian and Japanese birch seedlings grown in elevated CO(2) and temperature 总被引：1，自引：0，他引：1
The effects of increased CO(2) and temperature on the photosynthetic capacity of Siberian white birch and Japanese white birch (Betula platyphylla Sukatch. and B. platyphylla Sukatch. var. japonica Hara) were measured. Birch seedlings were raised with a CO(2) partial pressure of 36 +/- 0.3 Pa (i.e., ambient) or 70 +/- 0.6 Pa at day/night temperatures of either 30/16 degrees C or 26/12 degrees C. Siberian birch leaves were smaller and thicker than Japanese birch leaves. Water use efficiency and nitrogen use efficiency of Siberian birch grown in the CO(2)-enriched air were higher than those of Japanese birch. Both species showed a physiological adjustment to the growth CO(2) partial pressure. Carboxylation efficiency and quantum yield of both species grown in CO(2)-enriched air were lower than those of seedlings grown in ambient CO(2). The adaptation of Siberian and Japanese birch to elevated CO(2) and temperature are discussed in relation to predicted climate change. 相似文献
25.
TC Johnson CA Scholz MR Talbot K Kelts RD Ricketts G Ngobi K Beuning I Ssemmanda JW McGill 《Science (New York, N.Y.)》1996,273(5278):1091-1093
Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid. 相似文献