Impacts of shade on cattle well-being in the beef supply chain

Shade is a mechanism to reduce heat load providing cattle with an environment supportive of their welfare needs. Although heat stress has been extensively reviewed, researched, and addressed in dairy production systems, it has not been investigated in the same manner in the beef cattle supply chain. Like all animals, beef cattle are susceptible to heat stress if they are unable to dissipate heat during times of elevated ambient temperatures. There are many factors that impact heat stress susceptibility in beef cattle throughout the different supply chain sectors, many of which relate to the production system, that is, availability of shade, microclimate of environment, and nutrition management. The results from studies evaluating the effects of shade on production and welfare are difficult to compare due to variation in structural design, construction materials used, height, shape, and area of shade provided. Additionally, depending on operation location, shade may or may not be beneficial during all times of the year, which can influence the decision to make shade a permanent part of management systems. Shade has been shown to lessen the physiologic response of cattle to heat stress. Shaded cattle exhibit lower respiration rates, body temperatures, and panting scores compared with unshaded cattle in weather that increases the risk of heat stress. Results from studies investigating the provision of shade indicate that cattle seek shade in hot weather. The impact of shade on behavioral patterns is inconsistent in the current body of research, with some studies indicating that shade provision impacts behavior and other studies reporting no difference between shaded and unshaded groups. Analysis of performance and carcass characteristics across feedlot studies demonstrated that shaded cattle had increased ADG, improved feed efficiency, HCW, and dressing percentage when compared with cattle without shade. Despite the documented benefits of shade, current industry statistics, although severely limited in scope, indicate low shade implementation rates in feedlots and data in other supply chain sectors do not exist. Industry guidelines and third-party on-farm certification programs articulate the critical need for protection from extreme weather but are not consistent in providing specific recommendations and requirements. Future efforts should include: updated economic analyses of cost vs. benefit of shade implementation, exploration of producer perspectives and needs relative to shade, consideration of shade impacts in the cow–calf and slaughter plant segments of the supply chain, and integration of indicators of affective (mental) state and preference in research studies to enhance the holistic assessment of cattle welfare.     

熔喷过程湍流模型中的气流场数值模拟

以熔喷过程中的气流场为核心,建立熔喷过程的数学物理模型,采用数值模拟的方法进行研究。以Navier-Stocks方程为基础,应用基于同位网格的SIMPLER算法并行化计算气流场的速度分布,将试验测试值与数值模拟进行比较,结果表明:采用的数值模拟方法是有效的,完全可以用于模拟双槽钝头型模具的熔喷过程。     

玉米大斑病菌对广州地区甜玉米的致病性观测

通过对桂甜和华珍两个甜玉米品种的玉米大斑病病斑扩展速率及病情指数的研究结果表明,不同品种对玉米大斑病菌的抗性存在明显的差异;病斑的产孢特性显示,病斑首次产孢量显著高于再次产孢量。通过比较不同温度下的菌丝生长量,分析出广州地区玉米大斑病菌的主要构成属于高温型。     

Neuromagnetic evidence of spatially distributed sources underlying epileptiform spikes in the human brain

Neuromagnetic measurements were performed on 17 subjects with focal seizure disorders. In all of the subjects, the interictal spike in the scalp electroencephalogram was associated with an orderly extracranial magnetic field pattern. In eight of these subjects, multiple current sources underlay the magnetic spike complex. The multiple sources within a given subject displayed a fixed chronological sequence of discharge, demonstrating a high degree of spatial and temporal organization within the interictal focus.     

Growth of Stocker Channel Catfish to Large Market Size in Single-Batch Culture

Catfish farmers increasingly are producing fish larger than the traditional size of 0.45-0.57 kg/fish in order to meet processing plant requirements for larger fish. Production of larger channel catfish Ictalurus punctatus in multiple-batch culture has been investigated in a few studies, but the impact of understocked fingerlings on growth of carry-over fish is unknown. The present study was conducted to quantify growth, feed conversion ratio, net daily yield, and net and total yield of stocker channel catfish grown in single-batch, one-season culture to mean individual weights of 0.60, 0.72, 0.91, or 1.17 kg/fish. Channel catfish (mean weight = 0.26 kg/fish) were stocked into 12 0.1-ha ponds at 11,115 fish/ha. Fish were fed a 32% crude protein floating extruded feed once daily to apparent satiation. When the average weight of the fish population reached the target weight, three randomly selected ponds were harvested. Fish growth was linear in all treatments. Growth rates were similar for fish grown to 0.60, 0.72, and 0.91 kg/fish, and significantly lower ( P < 0.05) than for fish grown to 1.17 kg. Variation in individual fish weight increased linearly with increased duration of culture period. Feed conversion ratio averaged 1.9 and did not differ significantly among treatments. The percentage of the fish population at harvest that fell within the 0.57 to 2.04 kg-size range preferred by processing plants increased from 56.6 to 98-5% as the mean weight at harvest increased from 0.60 to 1.17 kg/fish.     

微量营养素可提高防病作用

微量元素和维生素在动物组织和细胞中是以功能性化学复合物存在的 ,不同的组织具有特定的浓度。要维持组织功能和结构的完整性 ,保证动物生长、健康和生产性能不受损害 ,组织中的微量元素和维生素浓度必须维持在一定的水平。微量元素和维生素缺乏、过高或不平衡都会导致其在体组织和体液中的存在形式和浓度变化 ,一旦高于或低于临界值 ,会引起生化变化 ,生理功能和结构损害 ,损害程度与微量营养素缺乏和中毒的程度、持续时间及动物个体有关 ,最有效的方法是在日粮中提供适当的微量营养素。微量营养素不足、中毒和比例不平衡。可能会出现代谢…     

虫生真菌在准格尔旗沙棘木蠹蛾上的流行

为了了解沙棘木蠹蛾Holcocerus hippophaecolus幼虫的虫生真菌的物种多样性和流行情况,对内蒙古准格尔旗某沙棘林中的虫生真菌进行了调查,采集到11个虫生真菌标本。经实验室显微观察鉴定,其中1个为雷州被毛孢Hirsutella leizhouensis侵染,1个为一种被毛孢Hirsutella sp.侵染,9个为球孢白僵菌Beauveria bassiana侵染;分离纯化得到7株球孢白僵菌菌株。     

浅析伊图里河林业局森林资源消长趋势

文章通过对伊图里河林业局1994年、2005年两次二类调查数据的分析,详细阐述了森林资源消长变化总趋势,在此基础上对伊图里河林业局森林资源现状及其特点进行了分析,提出了对森林资源管理利用的建议。     

Economic Interactions Between Feeding Rates and Stocking Densities in Intensive Catfish Ictalurus punctatus Production

Feed represents the largest cost input in intensive catfish Ictalurus punctatus production. Daily feed rations are generally related to stocking densities, up to a point at which high feeding rates begin to affect water quality. There has been no prior research to analyze the economic interactions between feeding and stocking rates. Econometric techniques were used to estimate a Just-Pope catfish production function, which was used to compute marginal products of inputs, and to identify stocking and feeding rates associated with the boundaries between Stages I, II, and III of the production function. Survey data collected by USDA National Animal Health Monitoring System were used for this analysis. Maximum yield, when accounting for both stocking and feeding rates, occurred at about 30,000 fingerlings/ha. However, profit-maximizing stocking densities ranged between 16,942 and 21,312 fingerlings/ha, depending upon expected catfish and feed prices. Farmers stocking at higher rates could be attempting to maximize yield instead of profit.