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41.
Wilson K Sammin D Harmeyer S Nath M Livingstone M Longbottom D 《Veterinary journal (London, England : 1997)》2012,193(2):583-585
Although few studies have investigated the prevalence of chlamydial infections in cattle, reported prevalence rates vary hugely. In order to assess the prevalence of this infection in cattle in Ireland, serum samples (100 herds, 20 samples/herd) collected for statutory screening for brucellosis were examined by soluble chlamydial antigen indirect ELISA. The assay detects antibodies to the two most common Chlamydiaceae spp. affecting cattle, namely Chlamydia abortus and Chlamydia pecorum. A total of 95 samples from 57 herds were seropositive, representing an observed prevalence rate of 4.75%. The parametric bootstrap estimate of the mean disease prevalence in the population was 6.04% (95%, CI 4.70-7.50). The results suggest the prevalence of chlamydial infection is low in cattle in Ireland. 相似文献
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Livingstone PG Ryan TJ Hancox NG Crews KB Bosson MA Knowles GJ McCook W 《Veterinary microbiology》2006,112(2-4):291-301
It is expected that the revised chapter on bovine tuberculosis in the Terrestrial Animal Health Code of the Office Internationale des Epizooties (OIE) will embrace regionalization as a functional means of assisting countries, states or regions to meet the requirements for freedom from tuberculosis and to facilitate trade. The benefits and applications of regionalization, which comprises zoning and compartmentalisation, are discussed. Regionalization requires that a country's veterinary administration is able to implement transparent and auditable biosecurity measures that will ensure that the tuberculosis-free status of a subpopulation of cattle is maintained despite the presence of infection in another cattle subpopulation, or in other domestic or wild animal species. Zoning, which requires cattle subpopulations to be separated by geographic boundaries, provides a practical basis whereby countries, states or regions, can progress towards freedom from tuberculosis, regardless of the source of infection for defined cattle subpopulations. Compartmentalisation however, requires that husbandry or management practices will be used to prevent a tuberculosis-free cattle subpopulation from contacting interspecific and intraspecific sources of infection. This will be difficult to achieve except for specialised cases such as artificial breeding centers. 相似文献
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The present study examined the effects of 17 beta-estradiol (E(2)) on in vitro maturation and subsequent in vitro fertilization of pig oocytes matured with or without cumulus cells. When E(2) (10 ng/ml) was added to the protein-free maturation medium, the proportions of cumulus-enclosed oocytes that underwent germinal vesicle breakdown and reached metaphase II were significantly reduced (P<0.05), and cumulus expansion was also significantly inhibited (P<0.05) compared with the control (no E(2) added). Although oocytes matured in the presence of E(2) were penetrated by sperm in vitro at the same level as the control, the incidences of male pronuclear (MPN) formation and activated oocytes were significantly lower (P<0.05) than the control. These inhibitory effects of E(2) were prevented when the medium was supplemented with E(2) together with its antagonist, ICI 182,780 (1 microg/ml), although the presence of the antagonist alone in the medium had no effect on the maturation and fertilization in vitro of oocytes. In cumulus-free oocytes, E(2) had no effect on nuclear maturation and penetration in vitro, but low MPN formation was observed in oocytes matured in the presence and absence of E(2). When cumulus-enclosed oocytes were cultured in the presence of progesterone (P(4); 600 ng/ml) alone or together with E(2), no significant differences in nuclear maturation, cumulus expansion or penetration in vitro were observed compared with control oocytes. The concentration of P(4) in maturation medium was significantly (P<0.01) lower when cumulus-enclosed oocytes were cultured for 44 h in the medium with E(2) than in medium without E(2). These results indicate that E(2) inhibits both nuclear and cytoplasmic maturation of cumulus-enclosed pig oocytes, and that this inhibition can be prevented by an E(2) antagonist or P(4). This E(2) inhibition may occur indirectly via the cumulus cells and inhibition of P(4) synthesis. 相似文献
47.
Luke C. N. Anglaaere Joseph Cobbina Fergus L. Sinclair Morag A. McDonald 《Agroforestry Systems》2011,81(3):249-265
Traditionally, most cocoa farms are established by removing the forest understorey and thinning the forest canopy so that
cocoa seedlings can grow into productive trees by utilising the forest rent of the newly cleared area and the shade provided
by the remaining trees. With the introduction of new hybrid cocoa varieties, there is a gradual shift towards the elimination
of shade trees in the cocoa landscape. Farmers have found it necessary to eliminate forest tree species to effect high performance
of these new varieties and as a result large areas of forested land are being lost, thereby posing a threat to biodiversity
A study was carried out in Atwima, a major cocoa farming district in the Ashanti region of Ghana, to assess the impact of
cocoa cultivation on tree diversity. The study also investigated farmers’ preferences for tree species retained on cocoa farms
as well as their traditional knowledge on tree species and their effect on cocoa cultivation. The assessment consisted of
identification and enumeration of all tree species with diameter at breast height greater than or equal to 10 cm, and was
carried out on one-hectare plots of: (a) Active Cocoa Farms (ACF), stratified into (i) Mature Cocoa Forest (MCF) and (ii)
Young Replanted Cocoa (YRC); (b) Fallow land (FL), and (c) Natural Forest (NF). A total of four one-hectare plots replicated
five times (or 20 ha) were enumerated. Tree diversity was more strongly influenced by landuse type than age of cocoa farm.
Fallow lands contained a higher tree diversity followed by natural forest, with the active cocoa farms, both mature and young,
containing the lowest variety of species. However, stem count was highest in the natural forest followed by FL and ACF. Generally,
stem counts of important tree species, as well as those classified as either endangered or vulnerable, were extremely low
in the landscape (0–2 per hectare), indicating a critical potential for conservation and rejuvenation. Farmers’ preference
for trees on cocoa farms was based on their usefulness. Three categories of trees emerged from their classification of trees
on cocoa farms: (i) naturally occurring trees that are very useful; (ii) naturally occurring species of minor economic use;
and (iii) naturally occurring tree species that are aggressive or incompatible with cocoa. Multistrata cocoa farms are a potential
niche for conservation, but given the current trends in cocoa replanting, future conservation strategies will have to focus
on identified targeted species which are of conservation concern, as well as those that are of value to farmers. 相似文献
48.
Carpenter KE Abrar M Aeby G Aronson RB Banks S Bruckner A Chiriboga A Cortés J Delbeek JC Devantier L Edgar GJ Edwards AJ Fenner D Guzmán HM Hoeksema BW Hodgson G Johan O Licuanan WY Livingstone SR Lovell ER Moore JA Obura DO Ochavillo D Polidoro BA Precht WF Quibilan MC Reboton C Richards ZT Rogers AD Sanciangco J Sheppard A Sheppard C Smith J Stuart S Turak E Veron JE Wallace C Weil E Wood E 《Science (New York, N.Y.)》2008,321(5888):560-563
The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. 相似文献
49.
Watson Stephen C. L. Newton Adrian C. Ridding Lucy E. Evans Paul M. Brand Steven McCracken Morag Gosal Arjan S. Bullock James M. 《Landscape Ecology》2021,36(12):3473-3491
Landscape Ecology - Agricultural intensification is being widely pursued as a policy option to improve food security and human development. Yet, there is a need to understand the impact of... 相似文献
50.
Nitrogenase activity associated with grasses is commonly reported to be maximal during reproductive growth. For Spartina alterniflora, a perennial grass growing in salt marshes, seasonal changes in potential (excised root) N2ase activity followed, by about 2 weeks, seasonal changes in ethanol soluble carbohydrate concentrations in roots and rhizomes. Both varied by about 3-fold during the year, declined rapidly with the onset of vegetative growth, and increased to previous levels during reproductive growth. N2-ase activity measured on intact systems in situ was also maximal during reproductive growth, but the absolute rates were much lower than the potential N2ase activities. 相似文献