Genetic variation in susceptibility to Marek's disease in a commercial broiler population.

Two commercial broiler pure lines that were previously identified to differ in their susceptibility to Marek's disease (MD) were line-crossed to generate an F1 population. Eight F1 males were randomly mated to four or five F1 females to produce an F2 test population that would be segregating for genes affecting MD. All F2 progeny (four hatches) were pedigreed at hatch and placed in colony houses as nonvaccinated. At 5 days of age, they were challenged intraabdominally with MD virus RB1B. Clinical signs, mortality, and gross and microscopic lesions were recorded during the MD challenge. At 8 wk postchallenge, all remaining birds were euthanatized and necropsied. During the MD challenge of the first two hatches, we observed that several severely stunted broilers originated from certain families and the differences in body weight among birds appeared as early as 3 wk postchallenge. To confirm this observation, body weight at 6 wk postchallenge was determined for all surviving birds in hatches 3 and 4 (n = 242). Genetic variation in body weight among broiler sire families was apparent; the average body weight for males at this time was 2.07 kg, whereas with females, it was 1.87 kg. At least 12.2% of the broilers, including both sexes, weighed less than 1 kg ("severely stunted") at this time. The incidence of these growth-stunted birds within each broiler sire family ranged from 0 to 26% and for dam families, 0 to 60%. Correlation analyses between stunting and other MD-associated traits revealed that the incidence of stunting had a significant and positive association with paralysis (r = 0.50). Therefore, the data suggest that there may be a genetic component affecting body weight loss during MD infection. The genetic component is speculated to affect susceptibility to MD paralysis with an indirect effect on the body weight of birds. The significance of this finding is best exemplified by the identification of a broiler sire family with over 26% of its progeny affected by this MD-associated trait.     

Improved detection of Mycobacterium avium subsp. paratuberculosis In milk by immunomagnetic PCR

The potential use of a novel immunomagnetic PCR (IMS-PCR) technique as a rapid method to screen milk samples for the presence of Mycobacterium avium subsp. paratuberculosis (M. ptb) was assessed. Immunomagnetic separation (IMS) for M. ptb, developed at Queen's University, Belfast, was applied to milk samples prior to IS900 PCR in order to selectively concentrate any M. ptb cells present and, at the same time, separate the cells from constituents of milk likely to inhibit subsequent PCR. This increased the sensitivity of IS900 PCR. IMS-PCR sensitivity could be further increased by initial centrifugation (2500 g for 20 min) of larger volumes of milk (10 and 50 ml), and resuspension of the sediment into a 1 ml volume appropriate for IMS treatment. Following IMS, template DNA for IS900 PCR was obtained by heating the bead-cell suspension in a thermal cycler at 100 degrees C for 15 min. It was estimated that the IMS-PCR assay could detect approximately 10(3)CFU of M. ptb per 50 ml of milk (equivalent to 20 CFU/ml), whereas the minimum detection limit of direct IS900 PCR was estimated at 10(5)CFU of M. ptb per 50 ml (equivalent to 2000 CFU/ml). A blind trial was carried out in which a total of 40 spiked (10(6)CFU M. ptb) and unspiked, raw and laboratory-pasteurised milk samples were independently tested by IMS-PCR and conventional IS900 PCR. IMS-PCR correctly identified 97. 5% of milk samples (sensitivity 100%, specificity 95%), including spiked milk samples before and after laboratory-pasteurisation. One false positive result was obtained which may have resulted from carryover between samples during the IMS procedure. Conventional IS900 PCR correctly identified only 72.5% of the same 40 milk samples (sensitivity 23%, specificity 100%). IMS-PCR was also shown to be capable of detecting natural M. ptb infection in raw sheep's milk, and raw and commercially pasteurised cows' milk.     

IPM Strategies and Their Dilemmas Including an Introduction to www. eurowheat.org

Information about disease management in winter wheat （Triticum aestiva） in eight European countries was collated and analysed by scientists and extension workers within the European Network for the Durable Exploitation of Crop Protection Strategies （ENDURE）. This included information about specific disease thresholds, decision support systems, host varieties, disease prevalence and pathogen virulence. Major differences in disease prevalence and economic importance were observed. Septoria tritici blotch （Mycosphaerella graminicola） was recognized as the most yield reducing disease in countries with intensive wheat production, but also rust diseases （Puccinia striiformis and Puccinia triticina）, powdery mildew （Blumeria graminis） and Fusarium head blight （Fusarium spp.） were seen as serious disease problems. Examples of current integrated pest management （IPM） strategies in different countries have been reported. Disease management and fungicide use patterns showed major differences, with an average input equivalent to 2.3 full dose rates （TFI） in the UK and a TFI of 0.6 in Denmark. These differences are most likely due to a combination of different cropping systems, climatic differences, disease prevalence, and socio-economic factors. The web based information platform www.eurowheat.org was used for dissemination of information and results including information on control thresholds, cultural practices which can influence disease attack, fungicide efficacy, fungicide resistance, and pathogen virulence, which are all elements supporting 1PM for disease control in wheat. The platform is open to all users. The target groups of EuroWheat information are researchers, advisors, breeders, and similar partners dealing with disease management in wheat.     

Isolation of Succinivibrionaceae implicated in low methane emissions from Tammar wallabies

The Tammar wallaby (Macropus eugenii) harbors unique gut bacteria and produces only one-fifth the amount of methane produced by ruminants per unit of digestible energy intake. We have isolated a dominant bacterial species (WG-1) from the wallaby microbiota affiliated with the family Succinivibrionaceae and implicated in lower methane emissions from starch-containing diets. This was achieved by using a partial reconstruction of the bacterium's metabolism from binned metagenomic data (nitrogen and carbohydrate utilization pathways and antibiotic resistance) to devise cultivation-based strategies that produced axenic WG-1 cultures. Pure-culture studies confirm that the bacterium is capnophilic and produces succinate, further explaining a microbiological basis for lower methane emissions from macropodids. This knowledge also provides new strategic targets for redirecting fermentation and reducing methane production in livestock.     

Bedout: a possible end-Permian impact crater offshore of northwestern Australia

The Bedout High, located on the northwestern continental margin of Australia, has emerged as a prime candidate for an end-Permian impact structure. Seismic imaging, gravity data, and the identification of melt rocks and impact breccias from drill cores located on top of Bedout are consistent with the presence of a buried impact crater. The impact breccias contain nearly pure silica glass (SiO2), fractured and shock-melted plagioclases, and spherulitic glass. The distribution of glass and shocked minerals over hundreds of meters of core material implies that a melt sheet is present. Available gravity and seismic data suggest that the Bedout High represents the central uplift of a crater similar in size to Chicxulub. A plagioclase separate from the Lagrange-1 exploration well has an Ar/Ar age of 250.1 +/- 4.5 million years. The location, size, and age of the Bedout crater can account for reported occurrences of impact debris in Permian-Triassic boundary sediments worldwide.