Use of molecular fingerprinting to assist the understanding of the epidemiology of Salmonella contamination within broiler production

1. We analysed Salmonella isolates by conventional sero- and phage-typing, as well as by molecular techniques within the broiler production chain in two integrated companies. The most prevalent serovars were selected for genetic fingerprinting. 2. Isolates were first screened by plasmid profiling; subsequently, the most common plasmid types within the prevalent zoonotic serovars (enteritidis and typhimurium) and S. agama were further characterised by PstI-SphI ribotyping, and XbaI pulsed field gel electrophoresis (PFGE). 3. Salmonella binza, S. kedougou, and S. 4,12:d:- were endemic in the feed mills over long periods of time, and a variety of plasmid types for each of the serovars were found in the premises. 4. A similar situation was found with S. binza and S. senftenberg within the hatchery in company B. The Salmonella serovars which were resident in those locations were also the ones most widely distributed throughout the broiler flocks. 5. Plasmid profiling was useful to subdivide clusters of isolates within serovars, but for each serovar a high percentage (36 to 79%) of the isolates tested fall within a prevalent plasmid type. 6. A more detailed genetic analysis of the isolates by a multiple typing approach allowed for further strain differentiation, and allowed some epidemiological conclusions to be drawn.     

玉米重组群体株型性状和生物学特性的遗传潜势与杂种优势研究

选用含有Reid、Lancaster及国内地方种血缘的自交系和品种作为基础材料,按血缘关系分别合成3个群体,再进行群体间杂交,以3个群体和6个群间杂交组合为试验材料,探讨群内遗传潜力和群间杂种优势.结果显示,株高（PH）、穗高（EH）、叶夹角（α）、叶向值（LOV）、播种至抽雄（STI）、播种至抽丝（SSI）、播种至成熟（SMI）和散粉至抽丝（ASI） 8个性状群体间遗传差异极显著;群间杂交后4个生育性状STI、SSI、SMI、ASI的杂种优势均为负值,株型性状株高（PH）、穗高（EH）、叶夹角（α）的杂种优势为正值,叶向值（LOV）的杂种优势为负值.表明合成的群体遗传基础丰富,群内变异较大,以群体为基础材料,可从中选育出优良自交系,组配出强优势杂交组合.     

A comparison of pooled and individual bird sampling for detection of Salmonella in commercial egg laying flocks

The objective of this study was to determine the sensitivity of culturing pooled samples containing varying numbers of individual droppings for detection of Salmonella in commercial egg-laying flocks relative to the within-flock prevalence. A laboratory experiment was performed to directly measure the effect of diluting positive with negative faeces on the sensitivity of detection, and thus provide priors for a Bayesian model of pooled sampling. Pooled samples made up of different numbers of individual faecal droppings were collected from 20 flocks, and in addition bulked faeces and dust were also sampled using an in-house method that involved collecting 10 dust and 10 faeces samples into jars with buffered peptone water. The results from these flocks were analysed using Bayesian methods for diagnostic test evaluation in the absence of a gold standard, and the sensitivity of each pooled sample type was estimated relative to the within-flock prevalence. The sensitivity of pooled samples depended on the within-flock prevalence, and increased as the prevalence increased. The sensitivity of pooled sampling tended to increase with the number of droppings in the pool, and overall there was a higher proportion of positive samples from the pools of 20, 60 and the in-house faeces pooling method compared to the pools of 10, 5 and the individual droppings. Dust samples were more sensitive than the faeces samples, and so the inclusion of dust in sampling schemes is recommended.     

产蛋鸡各阶段的饲养水平

生长期蛋用小母鸡的营养需要量一天与一天不一样,甚至产蛋开始后,还有变化。为使配合饲料能精确满足蛋用小母鸡不同生长阶段的营养需要,美国佛罗里达大学进行了这方面的试验研究。小母鸡的饲料配合美国国家科学院(NRC)建议,小母鸡在0-0周龄期间可喂同样的饲料,到6周龄末,所有的营养水平都应降低,14周龄末再次降低。事实上,鸡的营养需要量每两周之内并无明显不同。当然,这些营养水平只是鸡的平均需要量。因此可以推断,需要量是呈斜线降低的。 1985年Douglar等进行的两个试验,研究     

Prion biology relevant to bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) and chronic wasting disease (CWD) of deer and elk are a threat to agriculture and natural resources, as well as a human health concern. Both diseases are transmissible spongiform encephalopathies (TSE), or prion diseases, caused by autocatalytic conversion of endogenously encoded prion protein (PrP) to an abnormal, neurotoxic conformation designated PrPsc. Most mammalian species are susceptible to TSE, which, despite a range of species-linked names, is caused by a single highly conserved protein, with no apparent normal function. In the simplest sense, TSE transmission can occur because PrPsc is resistant to both endogenous and environmental proteinases, although many details remain unclear. Questions about the transmission of TSE are central to practical issues such as livestock testing, access to international livestock markets, and wildlife management strategies, as well as intangible issues such as consumer confidence in the safety of the meat supply. The majority of BSE cases seem to have been transmitted by feed containing meat and bone meal from infected animals. In the United Kingdom, there was a dramatic decrease in BSE cases after neural tissue and, later, all ruminant tissues were banned from ruminant feed. However, probably because of heightened awareness and widespread testing, there is growing evidence that new variants of BSE are arising "spontaneously," suggesting ongoing surveillance will continue to find infected animals. Interspecies transmission is inefficient and depends on exposure, sequence homology, TSE donor strain, genetic polymorphism of the host, and architecture of the visceral nerves if exposure is by an oral route. Considering the low probability of interspecies transmission, the low efficiency of oral transmission, and the low prion levels in nonnervous tissues, consumption of conventional animal products represents minimal risk. However, detection of rare events is challenging, and TSE literature is characterized by subsequently unsupported claims of species barriers or absolute tissue safety. This review presents an overview of TSE and summarizes recent research on pathogenesis and transmission.     

Long-term outcome of distal femoral osteotomy for treatment of combined distal femoral varus and medial patellar luxation: 12 cases (1999-2004)

OBJECTIVE: To determine long-term outcome of distal femoral osteotomy as a component of treatment for distal femoral varus and medial patellar luxation in large-breed dogs. DESIGN:Retrospective case series. ANIMALS: 12 dogs (16 stifle joints). PROCEDURES: Medical records and radiographs were reviewed to identify large-breed dogs with medial patellar luxation (grade > or = 2) and femoral varus angle > or = 12 degrees treated with distal femoral osteotomy, with a minimum follow-up (by a veterinarian) of 18 months. Signalment, weight, medial patellar luxation and lameness grade, pre- and postoperative femoral varus angle, surgical technique, time to radiographic bone union, and complications were recorded. Follow-up with owners via questionnaire was performed > 18 months after surgery. RESULTS: 16 corrective distal femoral osteotomies were performed with ancillary medial patellar luxation procedures in 12 dogs; 4 dogs had staged bilateral procedures. Mean +/- SD preoperative and postoperative femoral varus angles were 16.3 +/- 4.3 degrees and 3.9 +/- 2.5 degrees , respectively. Mean +/- SD time to radiographic union of the distal femoral osteotomy was 52.6 +/- 13 days. One dog had Kirschner wire migration from the tibial tuberosity. Patellar luxation was not detected after surgery in any dog. Mean +/- SD follow-up by a veterinarian was 1,335 +/- 410 days and by use of an owner questionnaire was 1,497 +/- 464 days. All 10 variables of owner-observed patient comfort and function were significantly improved. CONCLUSIONS AND CLINICAL RELEVANCE: Distal femoral osteotomy in combination with traditional treatment provided predictable osteotomy healing, patellar stabilization, and long-term improvement in patient comfort and function when used to treat combined distal femoral varus and medial patellar luxation in large-breed dogs.     

玉米南七单交高产密度与施肥水平的模型研究

试验采用4因素2次回归正交旋转组合设计,对四川省农作物品种审定委员会审定通过的、我所新选大穗型玉米杂交种南七单交的最优密度和最优化施肥同题进行了研究,以便为南七单交的进一步推广,发挥其增产潜力提供科学依据。试验设计方法一、试验设计采用4因素2次回归正交旋转组合设计,其因素与水平及编码值见表1,设3个正交区组,小区面积0.06亩,6行区,收中间2行计产。