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排序方式: 共有369条查询结果,搜索用时 15 毫秒
1.
M A Goodwin J Brown M A Smeltzer T Girshick S L Miller T G Dickson 《Avian diseases》1992,36(2):356-358
Antibody titers for infectious bursal disease virus (IBDV), infectious bronchitis virus, Newcastle disease virus, and reovirus from chicks with chicken anemia agent (CAA) antibodies were compared with antibody titers from their CAA-antibody-negative counterparts. These comparisons were made in 396 chickens that were 1 day, 2 weeks, 8-9 weeks, 10 weeks, 17 weeks, or 29-32 weeks old. Only one serum sample was collected from any given chick or chicken. There were no significant differences between the antibody titers at any age for any antigen, with one exception: at 29-32 weeks, the IBDV titers were higher (t = 2.62, df = 142, P less than 0.01) in chickens with CAA antibody. Although not at all likely, we believe that the observation of high IBDV antibody titers in CAA-antibody-positive chicks could have been a spurious one. 相似文献
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AE Jackson 《Australian veterinary journal》2015,93(12):431-432
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AE Jackson 《Australian veterinary journal》2016,94(11):395-396
5.
Context
North American grassland songbird populations have declined significantly due to habitat loss and fragmentation. Understanding the influence of the surrounding landscape on prairie fragment occupancy is vital for predicting the fate of grassland birds in these heavily altered landscapes.Objectives
We examined the relative importance of local and landscape variables on grassland bird occupancy of prairie fragments using a focal-patch study. We also investigated the spatial scale at which landscape variables were most influential.Methods
We surveyed birds on 29 unplowed prairie fragments in western Minnesota and eastern North and South Dakota. We quantified local habitat on the fragment using vegetation surveys and aerial photographs and the landscape surrounding the fragment out to 4 km using aerial photographs. We analyzed occupancy using multi-model approaches applied to multiple logistic regression.Results
Of 38 species encountered, nine were neither too rare nor too abundant to be analyzed. Predictors of patch occupancy were unique for each bird species, yet general patterns emerged. For eight species, landscape variables were more important than local variables. Mostly, those landscape variables measured configuration (e.g., edge density) and not composition (e.g., percent cover of a particular matrix element). Landscape effects were mostly from variables measured at the greatest extents from the prairie fragment.Conclusions
Using a focal-patch study design we demonstrated the importance of the surrounding landscape, often out to 4 km from the fragment edge, on prairie occupancy by grassland birds. Effective management of grassland songbirds will require attention to the landscape context of prairie fragments.6.
7.
Methods of assessing extinction risk in marine fishes 总被引:1,自引:0,他引:1
Nicholas K Dulvy Jim R Ellis Nicholas B Goodwin Alastair Grant John D Reynolds & Simon Jennings 《Fish and Fisheries》2004,5(3):255-276
The decline and disappearance of species from large parts of their former geographical range has become an important issue in fisheries ecology. There is a need to identify which species are at risk of extinction. The available approaches have been subject to considerable debate – particularly when applied to commercially exploited species. Here we have compiled methods that have been used or may be used for assessing threat status of marine organisms. We organize the methods according to the availability of data on the natural history, ecology and population biology of species. There are three general approaches to inferring or assessing extinction risk: (i) correlative approaches based on knowledge of life histories and ecology; (ii) time‐series approaches that examine changes in abundance; and (iii) demographic approaches based on age‐ or stage‐based schedules of vital rates and fisheries reference points. Many methods are well suited to species that are highly catchable and/or have relatively low productivity, but theory is less well developed for assessing extinction risk in species exhibiting narrow geographical distributions or ecological specialization. There is considerable variation in both definitions of extinction risk and the precision and defensibility of the available risk assessment methods, so we suggest a two‐tiered approach for defining and assessing extinction risk. First, simple methods requiring a few easily estimated parameters are used to triage or rapidly assess large numbers of populations and species to identify potentially vulnerable populations or species. Second, the populations and species identified as vulnerable by this process can then be subject to more detailed and rigorous population analysis explicitly considering sources of error and uncertainty. 相似文献
8.
AE Jackson 《Australian veterinary journal》2011,89(6):197-198
Computer model predictions and field observations of anthelmintic resistance in sheep · Dangers of off‐label use of barium selenate · Elbow luxation in dogs and cats · Prognosis of joint infections in adult horses · Omentalisation for mediastinal abscess in a dog · Adenoviruses in lizards 相似文献
9.
Michael J Mauel Debra L Miller Eloise Styer Deborah B Pouder Roy P E Yanong Andrew E Goodwin Thomas E Schwedler 《Journal of veterinary diagnostic investigation》2005,17(6):601-605
From 2001 to 2003, tilapia (Oreochromis sp.) farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 +/- 0.1 x 0.8 +/- 0.2 microm, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States. 相似文献
10.
Ribosomal DNA Sequence Comparisons of Colletotrichum Graminicola from Turfgrasses and other Hosts 总被引:1,自引:0,他引:1
T. Hsiang P.H. Goodwin 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(6):593-599
The 5.8S ribosomal gene and the flanking internal transcribed spacers (ITS) 1 and 2 from Colletotrichum graminicola isolates causing anthracnose disease of Agrostis palustris and Poa species were sequenced. Although bootstrap support was not high, two major groups were observed with both UPGMA and parsimony algorithms, one containing isolates from A. palustris and another with isolates from Poa spp. The ITS sequences were also compared with those of isolates of C. graminicola and C. sublineolum from Sorghum spp., Zea mays and Rottboellia cochinchinesis as well as other Colletotrichum species. Except for one isolate from P. annua in Texas, the ITS1 and ITS2 sequences of turfgrass isolates always grouped separately from C. graminicola or C. sublineolum from non-turfgrass hosts with high bootstrap support. ITS sequences of the turfgrass isolates were more similar to those of other species of Colletotrichum, such as C. coccodes and C. dematium, than they were to C. graminicola isolates from other hosts. Turfgrass isolates have ITS sequences which are not identical to those of isolates from Zea mays and Sorghum species demonstrating diversity among fungi conventionally classified as C. graminicola. 相似文献