A simulation model for predicting the voluntary feed intake of a growing pig

Abstract

The main goal of this simulator is to predict voluntary feed intake based on the effects of temperature and stocking density. The model indicates the limiting factors relative to diet (protein, energy or ash), housing environmental conditions and stocking density. The concepts of compensatory protein growth, correction of lipid growth, the desired feed intake to meet energy, protein and ash requirements, and influences of stocking density, genotype and sex are also introduced in this model. This study draws a flow chart and steps to predict feed intake of a growing pig to make it clear how the model works. The model simulates the outcomes of feed intake, energy and protein requirements for maintenance, the energy cost for cold thermogenesis, and protein and lipid retention on a daily basis until slaughter weight. This model was also validated by comparison with published experiments.     

稀释率对新型固液气分流式瘤胃模拟系统发酵效果的影响

本试验旨在研究稀释率对新型固液气分流式瘤胃模拟系统发酵效果的影响.采用单因子完全随机试验设计,共设4个处理,各处理稀释率分别为6％/h、8％/h、10％/h、12％/h,每个处理3个重复,每个重复1个发酵罐.试验期10 d.结果表明:随着稀释率的提高,发酵液pH极显著提高(P＜0.01),而氨态氮(NH3-N)浓度则极显著降低(P＜0.01).稀释率由6％/h上升到10％/h,总挥发性脂肪酸(TVFA)及戊酸浓度极显著下降(P＜0.01).稀释率从6％/h提高到8％/h时,原虫数量极显著提高了6.91％ (P ＜0.01),但当稀释率从8％/h提高到12％/h时,原虫数量却极显著下降了5.18％ (P ＜0.01).随着稀释率从6％/h增加到10％/h,木聚糖酶活性(P＜0.01)及微生物蛋白质(MCP)产量(P＜0.05)显著或极显著降低,粗蛋白质体外消失率极显著升高(P＜0.01).稀释率为10％/h和12％/h的2个处理,中性洗涤纤维体外消失率显著高于另外2个处理(P＜0.05).结果提示,稀释率能够影响新型固液气分流式瘤胃模拟系统的发酵情况,稀释率为8％/h时,原虫数量以及纤维素类酶活性、各瘤胃发酵参数更加有利于发酵,因此可推荐作为本系统最优运行条件.     

浅论城市道路景观营造要素

指出了城市道路景观营造是道路景观营造的重要组成部分,从城市道路景观中的静态景观和动态景观两方面阐述了景观营造的相关内容,归结出了城市道路景观营造的原则,以为城市道路景观营造、城市道路景观分析与评价提出合理的、人性化的依据。     

毛细管网吊顶辐射空调与新风耦合的性能研究

对毛细管网结构研发及供冷性能进行测试,并应用 Fluent数值模拟,对毛细管辐射供冷末端与置换通风和贴附射流两种通风方式加以耦合,通过实验验证了其模拟模型对该实验系统具有相关适用性,并应用了该相关模型。结果表明：两种不同的送风方式下,房间的三度均能满足舒适性要求,当热湿负荷突然增加时,如不采取相应的响应动作,毛细管辐射板表面将会有结露现象发生,置换通风较为严重,相同的新风条件下,贴附射流的通风方式,对于消除辐射板结露效果明显。     

水力旋流器的三维模拟

利用RSM模型模拟计算三维水力旋流器模型,分析了计算结果,并且与相关文献比较后认为：三维模型模拟水力旋流器具有一定的可行性,而二维轴对称模型与实际有一定的差距。     

Variation in selected solid wood properties of young Pinus patula from diverse sites in the Mpumalanga escarpment area in South Africa

Regression analyses identified ‘Growth Days’ (an index expressing site moisture availability) as the only site variable contributing significantly to the prediction to wood density (R² = 0.57), whereas the model predicting grain angle included only ‘Altitude’ (R² = 0.60). These results surfaced during an investigative study to quantify various sources of variation in wood properties and to quantify the effect of a number of site factors on wood properties of Pinus patula grown in the Mpumalanga escarpment area of South Africa. For this purpose, 10 trees were sampled from each of 17 diverse sites for wood property analyses. The effects of site, distance from the pith and differences between trees within site on wood density, transverse shrinkage, grain angle and dynamic modulus of elasticity were investigated. The site factors considered included a wide variety of soil and climatic factors. The effect of radial distance from the pith and differences between individual trees within sites were highly significant, accounting for most of the variation in wood properties. Although the effects of a number of site factors were statistically significant, they generally explained relatively small but important variation in wood properties among sites. The study not only quantified the effects of important sources of variation on a few key wood properties, but it also revealed that the extent of differences between sites can be explained in terms of some specific site factors. It is envisaged that the results will contribute significantly towards the refinement of current forest site classification systems for improved decision-making with respect to wood quality in intensively managed plantation systems.     

Track Counts as a Means of Estimating Population Densities of Bushbuck

Counts of bushbuck tracks were used to estimate their population densities. Good correlations were obtained between various indices of track frequency and estimated absolute population density. The technique is therefore recommended for assessing the absolute density of a population. High sampling costs, however, disqualify the technique for detecting small changes in density.     

Agroforestry Systems for Food and Nutrition Security–Potentials,Pathways and Policy Research Needs

SUMMARY

Food insecurity and malnutrition continue to be the most daunting development challenges in most developing countries. Increases in the productivity of cereal grain crops have helped many developing countries achieve self-sufficiency in meeting the energy requirements, but malnutrition still exist. Agroforestry–growing useful tree crops with annual crops–could provide a solution to food security micronutrient malnutrition. The paper develops a conceptual framework for identifying pathways of how agroforestry systems can contribute to nutrition security and its potential as a food-based nutrition intervention. Furthermore, a theoretical framework for studying the interactions of agroforestry and nutrition security is developed. Finally, policy implications and research needs are identified.     

Effect of donor animals and their diet on in vitro nutrient degradation and microbial protein synthesis using grass and corn silages

Two nonlactating cows and two wether sheep, all fitted with a permanent cannula into the rumen, were fed either hay plus concentrate, grass silage or corn silage to study the effect of the donor animal and its diet on in vitro fermentation and microbial protein synthesis. Rumen inoculum was obtained before the morning feeding. Grass silage or corn silage was incubated in a semi‐continuous rumen simulation system for 14 days. Four replicated vessels were used per treatment. Degradation of crude nutrients and detergent fibre fractions as well as microbial protein synthesis and the production of volatile fatty acids were studied. Additionally, total gas and methane production was measured with a standard in vitro gas test. Gas production and methane concentration was higher when the inoculum used was from sheep than that from cows. The donor animal also affected the degradation of organic matter and ether extract as well as the amount of propionate and butyrate, and the acetate‐to‐propionate ratio. The effect of the diet fed to the donor animal on fermentation was much greater than the effect of the donor animal itself. Feeding hay plus concentrate resulted in higher gas production and degradation of acid detergent fibre, but in lower degradation of ether extract and reduced microbial protein synthesis. Additionally, the pattern of volatile fatty acids changed significantly when the diet of the donor animals was hay plus concentrate or one of the silages. These results show that in vitro fermentation and microbial protein synthesis is different when based on inoculum from either cattle or sheep. The diet fed to the donor animal is more important than the animal species and is probably mediated by an adjusted microbial activity. With regard to standardized feed evaluations, these results further support the need to harmonize in vitro approaches used in different laboratories.     

基于模糊控制与RBF神经网络的桃树病虫害发生预测

将模糊控制引入到径向基函数(RBF)神经网络中,采用模糊控制与RBF神经网络相结合的方式建立预测模型,对河北顺平地区种植的桃树进行病虫害发生预测.仿真结果表明,该预测模型相对误差小,并解决了人工神经网络缺乏处理不确定性和模糊信息能力的缺点,预测预报及时、准确.