Assessing performance of feedlot operations using epidemiology.

The progressive feedlot veterinarian must be well versed not only in individual production animal medicine, but also in population-based medicine. Feedlot health programs must be goal oriented, and evaluation of these goals is accomplished through diligent use of record systems and analytic evaluation of these record systems. Basic feedlot monitoring parameters include health and economic parameters in addition to the use of bench marking parameters between and among feed yards. When these parameters have significant changes, steps should be initiated to begin field investigations. Feedlot epidemiology uses several novel applications such as partial budgeting, risk assessment, and packing plant audits to provide scientifically sound and economically feasible solutions for the feeding industry.     

几种观赏型沉水植物对富营养化蓝绿藻类的抑制作用

一些大型沉水植物种类的存在对“水华”藻类的生长具有抑制作用,其主要机制是水生高等植物不仅与藻类竞争营养、光照和生长空间等生态资源,而且还可以向水中分泌具有抑制藻类生长的化感物质。通过连续滴加种植水的方式研究了3种观赏型沉水植物矮慈菇（Sagittaria pygmaea Miq）、杉叶藻（Hippuris vulgaris.）、石龙尾（Limnophila heterophylla）对5种富营养化淡水藻,蓝藻：铜绿微囊藻（Microcystis aerugnasa）、纤维席藻（Phormidium tenue）;绿藻：衣藻（Chlamy domonas sajao）、四尾栅藻（Scenedesmus quaclricauda）、小球藻（Chlorella pyrenoidosa）的抑制作用。研究结果表明：（1）矮慈菇种植水对铜绿微囊藻、四尾栅藻、纤维席藻的生长没有影响,对小球藻的生长具有促进作用,对衣藻的生长具有明显的抑制作用;（2）杉叶藻种植水小球藻、衣藻和纤维席藻的生长没有影响,对四尾栅藻的生长具有促进作用,对铜绿微囊藻生长具有明显的抑制作用;（3）石龙尾种植水对小球藻、四尾栅藻、纤维席藻都具有明显的抑制作用,对铜绿微囊藻的生长没有影响,对衣藻的生长具有促进作用。3种沉水植物中,石龙尾的抑藻能力最强,矮慈菇和杉叶藻次之,石龙尾的化感抑藻效应更具有广谱性,在富营养化水体中与蓝绿藻类的竞争更具有优势,比较适用于改善城市景观水体水环境质量。     

柑桔黄龙病亚洲种病原的PCR-SSCP分析

应用PCR—SSCP技术对采自我国柑桔主产区、泰国和法国留尼湾等8个不同地方的柑桔黄龙病亚洲种的病原(Candidatus Liberibacter asiaticus)进行研究。对引物P1、P2扩增的PCR产物进行SSCP分析，得到两条清晰且泳动速率一致的条带，表明不同地方柑桔黄龙病亚洲种病原扩增的DNA片段之间没有差异。     

樱桃叶片的光合特性研究

以那翁、斯坦勒和佐藤锦3个樱桃栽培品种为材料,利用CIRAS-2便携式光合测定仪,研究了樱桃不同枝条节位、不同叶幕层和方位上叶片的光合特性.结果表明:樱桃新梢不同节位叶片Pn呈单峰变化,中部5~7节叶片Pn值的最高,梢部叶片Pn值最低.不同叶幕层Pn存在显著差异,3个樱桃品种Pn值均为外层>上层>中层>内层.3个品种不同方位叶片Pn值大小均为南面>东面>西面>北面,南面叶片Pn值最高,与其它方位Pn值差异显著.3个樱桃品种间不同叶位Pn值佐藤锦最高,斯坦勒次之,那翁最低.     

Tissue distribution, elimination, and metabolism of dietary sodium [36Cl]chlorate in beef cattle

Two steers (approximately 195 kg) were each dosed with 62.5 or 130.6 mg/kg body weight sodium [36Cl]chlorate for three consecutive days. All excreta were collected during the dosing and 8 h withdrawal periods. The apparent radiochlorine absorption was 62-68% of the total dose with the major excretory route being urine. Parent chlorate was 65-100% of the urinary radiochlorine; chloride was the only other radiochlorine species present. Similarly, residues in edible tissues were composed of chloride and chlorate with chloride being the major radiolabeled species present. Chlorate represented 28-57% of the total radioactive residues in skeletal muscle; in liver, kidney, and adipose tissues, chlorate ion represented a smaller percentage of the total residues. Chlorate residues in the low dose steer were 26 ppm in kidney, 14 ppm in skeletal muscle, 2.0 ppm in adipose tissue, and 0.7 ppm in liver. These data indicate that sodium chlorate may be a viable preharvest food safety tool for use by the cattle industry.     

Mechanical transmission of porcine reproductive and respiratory syndrome virus throughout a coordinated sequence of events during cold weather

Using a field-based model, mechanical transmission of porcine reproductive and respiratory syndrome virus (PRRSV) was assessed throughout a coordinated sequence of events that replicated common farm worker behavior during cold weather (< 0°C). The model involved fomites (boots and containers), vehicle sanitation, transport, and the movement of personnel. A field strain of PRRSV was inoculated into carriers consisting of snow and water, and carriers were adhered to the undercarriage of a vehicle. The vehicle was driven approximately 50 km to a commercial truck washing facility where the driver's boots contacted the carriers during washing, introducing the virus to the vehicle interior. The vehicle was then driven 50 km to a simulated farm site, and the driver's boots mechanically spread virus into the farm anteroom. Types of containers frequently employed in swine farms (styrofoam semen cooler, metal toolbox, plastic lunch pail, and cardboard animal health product shipping parcel) contacted drippings from footwear on the anteroom floor. The truck wash floor, vehicle cab floor mats, boot soles, anteroom floor, and the ventral surface of containers were sampled to track the virus throughout the model. Ten replicates were conducted, along with sham-inoculated controls. At multiple sampling points PRRSV nucleic acid was detected in 8 of 10 replicates. In each of the 8 PCR-positive replicates, infectious PRRSV was detected on the surfaces of containers by virus isolation or swine bioassay. All sham-inoculated controls were negative. These results indicate that mechanical transmission of PRRSV can occur during coordinated sequence of events in cold weather.     

Evaluation of mosquitoes, Aedes vexans, as biological vectors of porcine reproductive and respiratory syndrome virus

The objective of this study was to determine whether mosquitoes, Aedes vexans (Meigen), could serve as biological vectors of porcine reproductive and respiratory syndrome virus (PRRSV). Specifically, the study assessed the duration of viability and the site of PRRSV within mosquitoes, and evaluated whether PRRSV could be transmitted to a susceptible pig by mosquitoes following a 7- to 14-day incubation period after feeding on an infected pig. For the first experiment, a total of 100 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV (day 7 post-inoculation) and were then maintained alive under laboratory conditions. A set of 10 mosquitoes were collected at 0 hour (h), 6 h, 12 h, 24 h, 48 h, 72 h, 5 days (d), 7 d, 10 d, and 14 d post-feeding (pf). Samples of exterior surface washes, salivary glands, thorax carcasses, and gut homogenates were collected from each set of mosquitoes, and tested for PRRSV. Infectious PRRSV was detected by polymerase chain reaction and swine bioassay only from the gut homogenates of mosquitoes collected at 0 h and 6 h pf. For the second experiment, a total of 30 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV and the mosquitoes were then maintained under laboratory conditions. On each of day 7, 10, and 14 pf, a set of 10 mosquitoes were allowed to feed on a susceptible pig. Transmission of PRRSV to susceptible pigs did not occur, and PRRSV was not detected from the mosquitoes. These findings indicate that mosquitoes are not likely to serve as biological vectors of PRRSV.     

An evaluation of test and removal for the elimination of porcine reproductive and respiratory syndrome virus from 5 swine farms.

The objective of this field study was to evaluate the protocol of test and removal (T&R) for the elimination of porcine reproductive and respiratory syndrome virus (PRRSV) from 5 chronically infected breeding herds. The T&R protocol involved sampling the entire breeding herd in one day, testing sera by polymerase chain reaction and ELISA to detect previously exposed and/or infected animals, and subsequently removing them from the herd. Following completion of T&R, breeding herds were monitored for 12 consecutive months, using ELISA, for the presence of antibodies to PRRSV. In order to be classified as a PRRSV-negative herd, all samples collected over the 12-month monitoring period were required to be negative by ELISA (s/p ratio < 0.4). At the conclusion of the monitoring period, all 5 farms were PRRSV-negative, according to the defined testing criteria. Approximately 2.2% (74/3408) ELISA false positive samples were detected across all 5 farms during the monitoring period. The diagnostic cost required during the T&R protocol was approximately US $10.66 per animal tested. Limitations of the study were a lack of herds with large (> 2000 sows) breeding herd inventories, and herds with a history of PRRSV vaccination.     

Lateral ligamentous injury to the carpus of a racing greyhound

The lateral collateral ligament of the ulna and the dorsolateral ligaments of the radiocarpal joint of a racing Greyhound were ruptured, resulting in instability of the carpus when the joint was flexed. This report describes a technique for making a ligament prosthesis, using the ulnaris lateralis tendon. Although the dog did not return to racing, the carpus was stable enough for general activity.