畜群规模的结构决策研究

结构和规模是影响草地放牧生态系统功能实现的重要因素。本文通过建立和分析畜群种群动态模型, 揭示了母畜结构参数是影响畜群规模唯一因素的一般规律：（１） 当１２ ∑ｒｉ＝ １ｂｉ ∏ｉｊ＝ １ ｑｉ,ｊ－ １ｐｉ,ｊ－ １ （１ － ｓｉ,ｊ－ １）（１ － （１ － ｑｉ,ｊ－ １） ｐｉ,ｊ－ １ （１ － ｓｉ,ｊ－ １）） ＝ １ 时, 畜群规模稳定, 基本保持不变;（２） 当１２ ∑ｒｉ＝ １ｂｉ ∏ｉｊ＝ １ ｑｉ,ｊ－ １ｐｉ,ｊ－ １ （１ － ｓｉ,ｊ－ １）（１ － （１ － ｑｉ,ｊ－ １） ｐｉ,ｊ － １ （１ － ｓｉ,ｊ－ １）） ＜ １ 时, 畜群规模呈下降趋势,最终趋近于零;（３） 当１２ ∑ｒｉ＝１ｂｉ ∏ｉｊ＝ １ ｑｉ,ｊ－ １ｐｉ,ｊ－ １ （１ － ｓｉ,ｊ－ １）（１ － （１ － ｑｉ ,ｊ－ １） ｐｉ,ｊ－ １ （１ － ｓｉ,ｊ－ １）） ＞ １ 时, 畜群规模随年度不断膨胀, 并最终突破系统的承载能力。     

Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC相似文献   

Closed system anaesthesia in dogs using liquid sevoflurane injection; evaluation of the square-root-of-time model and the influence of CO2 absorbent

Objective To determine whether predictable alveolar concentrations of sevoflurane are reliably produced in dogs when liquid sevoflurane is injected into closed circuit breathing systems, as calculated by Lowe's square‐root‐of‐time anaesthetic uptake model, and to confirm the validity of the model using soda lime and calcium hydroxide lime. Study design Prospective clinical study. Animals Eleven healthy dogs with a mean body mass of 34 ± 9 kg scheduled for pelvic limb orthopaedic surgery. Materials and methods Following pre‐anaesthetic medication, anaesthesia was induced with propofol and maintained with sevoflurane in a closed circle system. Epidural anaesthesia was performed with morphine and bupivacaine. Liquid sevoflurane was injected into the circuit by syringe, using dosages and time intervals derived from Lowe's square‐root‐of‐time anaesthetic uptake model. The target alveolar concentration chosen was 1.1 × MAC (2.6% end‐tidal sevoflurane). Either soda lime (group S; n = 6) or calcium hydroxide lime (Amsorb; group A; n = 5) were used for CO₂ absorption. Sevoflurane concentration and the respiratory gas composition were measured with an infrared gas analyser. Results End‐tidal sevoflurane concentrations were close to the predicted value of 2.6% at 9 minutes (2.53 ± 0.1% group S; 2.60 ± 0.26% group A) and 16 minutes (2.55 ± 0.30 group S; 2.52 ± 0.28% group A) but declined thereafter to reach 50% (group S) and 64% (group A) of the predicted value at 121 minutes. There was a constant trend towards higher end‐tidal sevoflurane concentrations in group A but the difference was not statistically significant. Conclusions The square‐root‐of‐time model leads to significantly lower alveolar concentrations than expected, suggesting that the rate of sevoflurane uptake in dogs declines less rapidly than predicted. The use of Amsorb tends to reduce the deviation from predicted concentrations. Clinical relevance The model used in this study provided only an approximate guide to the volume of liquid sevoflurane required. Consequently, the definitive dose schedule must be based on measured anaesthetic concentrations and clinical monitoring.     

Murine xenograft model demonstrates significant radio-sensitising effect of liposomal doxorubicin in a combination therapy for Feline Injection Site Sarcoma

Therapy of cats suffering from feline injection site sarcomas (FISS) is still a challenging problem, as the recurrence rate after surgery is up to 70%. Four FISS-derived primary tumour cell lines and corresponding xenograft tumour mouse models were established to evaluate the efficacy of a concomitant chemo-/radiation therapy with doxorubicin. In vitro, strongly depending upon the timing of administration, pre-treatment with 0.25 µmol doxorubicin resulted in a significant enhancement of radiation-induced (3.5 Gy) tumour cell death. This result was confirmed in vivo, where only the combined chemo-/radiation therapy resulted in a significant reduction in tumour growth compared to the respective mono-therapies with either doxorubicin or radiation. These results support the use of the concomitant chemo-/radiation therapy for adjuvant treatment of FISS, particularly in advanced or recurrent disease where surgery alone is no longer feasible.     

乳牛体型性状线性评定数学模型的指导和应用

本文说明了乳牛体型性状线性评定的常规方法,在此基础上推导出了该评定方法的数学模型。该模型的提出,极大地简化了常规评定方法的繁琐计算,值得在乳牛业生产实践中推广使用。     

Genetic parameters for abnormal sucking traits in Austrian Fleckvieh heifers

Cross‐sucking and intersucking are considered abnormal behaviours in cattle and constitute a common problem in dairy farming. Cross‐sucking in calves is defined as sucking any body parts of another calf whereas intersucking in heifers and cows is defined as sucking the udder or udder area. The aim of this study was to determine the genetic variability for abnormal sucking behaviour by estimating genetic parameters and examining individual differences between sires with large progeny groups. By means of a questionnaire, cattle breeders in the federal state Lower Austria were requested to identify all currently kept animals which are known of either inter‐ or cross‐sucking (both defined as the same binary trait ‘sucking’ with 0 and 1 referring to the absence and presence of this abnormal behaviour) or allowing sucking (also treated as a binary trait, scored as 1 if an animal was known of allowing herd mates to suck and 0 otherwise). Records of 1222 farms and 13 332 dual purpose Simmental females aged between 21 and 700 days were investigated applying a linear animal model with fixed herd × year × season and random genetic animal effect and a threshold sire model with the herd × year × season effect being treated as random. In total, 8.6% and 4.1% of all calves/heifers were observed sucking and allowing sucking, respectively. Heritabilities of 0.040 ± 0.014 and 0.007 ± 0.006 (linear animal model) and 0.116 ± 0.041 and 0.026 ± 0.024 (threshold model) were found for the traits sucking and allowing sucking, respectively. Breeding values were estimated applying the same models for the trait sucking. Taking all 254 sires into account, the Pearson and Spearman correlation coefficients between breeding values estimated by linear animal and sire threshold model were 0.86 and 0.80. Thus, little difference was observed between the two methods.     

牧草-鹅-鲜食葡萄循环生态种养模式的构建与实践

为了提高葡萄园资源利用率和综合效益,构建了牧草-鹅-鲜食葡萄循环生态种养体系。实践表明,在设施葡萄园推广套种牧草养鹅、鹅粪生产有机肥料、有机肥料种植葡萄和牧草等高效配套技术,取得了良好的经济效益、生态效益和社会效益。实施牧草-鹅-鲜食葡萄循环生态种养是江苏沿海地区发展现代农业的一种有效生产模式。     

临界氮浓度稀释模型在牧草种子生产中的应用前景

氮素是影响牧草种子产量的关键因素,氮素对于植株分蘖、干物质生产、花序形成、产量组分动态变化等均具有影响.文章主要从临界氮浓度稀释模型的概念、构建方法、研究现状、应用等方面进行了综述,提出临界氮浓度稀释模型在实际生产中应用时存在的问题,并对其在牧草种子生产中的应用前景进行了展望.     

《家禽生产学》培养学生实践能力教学模式的建立

从大学教育中注重学生实践能力培养的重要性入手,对作者在《家禽生产学》专业教学中总结出的专业课《家禽生产学》的教学模式进行探讨,旨在提出一种新的思路——如何在专业课教学中培养学生的实践操作能力,以切实提高课程的教学效果,使学生在毕业后走向工作岗位时,既具有扎实的理论知识,又具有和娴熟的实践技能。     

Muscle reorganisation through local injection of stem cells in the diaphragm of mdx mice

Background

The diaphragm is the major respiratory muscle affected by Duchenne muscular dystrophy (DMD) and is responsible for causing 80% of deaths. The use of mechanical forces that act on the body or intermittent pressure on the airways improves the quality of life of patients but does not prevent the progression of respiratory failure. Thus, diseases that require tissue repair, such as DMD, represent a group of pathologies that have great potential for cell therapy. The application of stem cells directly into the diaphragm instead of systemic application can reduce cell migration to other affected areas and increase the chances of muscle reorganisation. The mdx mouse is a suitable animal model for this research because its diaphragmatic phenotype is similar to human DMD. Therefore, the aim of this study was to assess the potential cell implantation in the diaphragm muscle after the xenotransplantation of stem cells.

Methods

A total of 9 mice, including 3 control BALB/Cmice, 3 5-month-old mdx mice without stem cell injections and 3 mdx mice injected with stem cells, were used. The animals injected with stem cells underwent laparoscopy so that stem cells from GFP-labelled rabbit olfactory epithelium could be locally injected into the diaphragm muscle. After 8 days, all animals were euthanised, and the diaphragm muscle was dissected and subjected to histological and immunohistochemical analyses.

Results

Both the fresh diaphragm tissue and immunohistochemical analyses showed immunopositive GFP labelling of some of the cells and immunonegativity of myoblast bundles. In the histological analysis, we observed a reduction in the inflammatory infiltrate as well as the presence of a few peripheral nuclei and myoblast bundles.

Conclusion

We were able to implant stem cells into the diaphragm via local injection, which promoted moderate muscle reorganisation. The presence of myoblast bundles cannot be attributed to stem cell incorporation because there was no immunopositive labelling in this structure. It is believed that the formation of the bundles may have been stimulated by cellular signalling mechanisms that have not yet been elucidated.