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1.
OBJECTIVE: To investigate the development of immune responses in calves experimentally and naturally infected with Mycobacterium paratuberculosis and to evaluate the potential for diagnostic tests to detect infected calves. DESIGN: Sequential testing of four treatment groups of calves over a 2 year period. PROCEDURE: Twenty-nine calves were allocated to four groups. Group D calves were orally dosed with M paratuberculosis, group N calves naturally exposed to M paratuberculosis, group V calves vaccinated for M paratuberculosis, and group C were control calves (not infected or vaccinated). Blood and faecal specimens were collected from each calf at monthly intervals to 18 months of age and then every 2 months until they were slaughtered between the ages of 21 and 29 months. Specimens were tested using absorbed EIA, IFN-gamma EIA and faecal culture. The infection status of the calves was confirmed by extensive histopathological examination and tissue culture. RESULTS: M paratuberculosis infection was confirmed in 10 calves, comprising six of eight orally dosed calves, three of five naturally exposed calves and one of nine vaccinated calves. The six artificially infected calves and one naturally infected calf were detected shedding M paratuberculosis in their faeces. Results with positive absorbed EIA were obtained from one artificially infected calf, one naturally infected calf and three vaccinated calves. All calves including controls had positive results on at least one occasion using the IFN-gamma EIA. In addition, seven calves had positive bovine tuberculosis results using the IFN-gamma EIA, even though bovine tuberculosis has been eradicated from Australia. CONCLUSION: Detection of M paratuberculosis infection in young cattle continues to be difficult using current tests. 相似文献
2.
OBJECTIVE: To determine the sensitivity and specificity of an absorbed ELISA and an AGID test for the detection of clinical and subclinical paratuberculosis in sheep. DESIGN: By testing a panel of sera from 1257 Australian Merino and crossbred sheep greater than 1 year of age, of which 1137 sheep were not infected with Mycobacterium avium subsp paratuberculosis and 120 sheep had paratuberculosis. PROCEDURE: Sera were collected from 457 sheep in Victoria and 800 sheep in Western Australia. Presence of M a paratuberculosis infection in Victorian sheep was determined by histological examination of intestinal tissues, whereas sheep from Western Australia were presumed to be free of Johne's disease. The ability of an absorbed ELISA to discriminate between infected and uninfected sheep was described by test sensitivity and specificity, the distribution of ELISA OD, and the area under a receiver operating characteristic curve. RESULTS: The absorbed ELISA had a specificity of 98.2 to 99.5% (CI) and a sensitivity of 35 to 54% (CI). In sheep from infected flocks in Victoria, the AGID test had a specificity of 99 to 100% (CI) and a sensitivity of 38 to 56% (CI). The sensitivity of serological tests was higher in sheep with a body condition representative of the lower quintile of their flock of origin. CONCLUSION: The AGID test and absorbed ELISA are useful tests for the detection of ovine paratuberculosis. Although the tests had a similar accuracy, they detected different subpopulations of infected sheep with only moderate overlap. The AGID test had a higher specificity than the absorbed ELISA. 相似文献
3.
Organic residues provide the fundamental energy supply supporting soil fungal communities. Provision of adequate energy is required for soil microbial communities to adapt and function in the presence of ecological stress, such as copper (Cu) contamination. However, contamination can also lead to decreased ecological fitness of microorganisms, limiting their ability to access substrates. Thus, complex interactions exist between substrates, metals, energy supply/accessibility, fungal communities and their processes, and these have implications for ecosystem processes. We investigated the interaction between energy resources and Cu tolerance on soil fungal communities, including Fusarium and Trichoderma (model disease causing and beneficial genera). Using quantitative PCR and DGGE fingerprinting, the effects of increasing soil Cu levels (0 to >3000 mg Cu kg−1 soil) on size and structure of soil fungal communities were tested under basal and plant-residue (medic; Medicago trunculata) added conditions. The interaction between increasing soil Cu levels and the addition of plant resources on fungal community structure was tested using multivariate analysis. The relative size (DNA copies per unit of soil DNA) of soil fungal communities, including Trichoderma and Fusarium, significantly (P < 0.05) increased (94% and 32% respectively) with addition of medic to soil. In medic-applied samples, the bacterial to fungal ratio decreased, demonstrating the selective influence of the cellulose-rich substrate on the fungal community. Under the high nutrient conditions fungal DNA increased as a fraction of the total soil DNA, demonstrating the tolerance of fungi to Cu (relative to other microbiota) given adequate energy resources. Copper had no impact on the abundance of Fusarium or Trichoderma, but significantly affected community structure (PERMANOVA; P < 0.05). With increasing Cu, species selection and replacement could be observed, particularly in soils where medic had been included. Plant residue addition itself was a highly selective factor affecting the structure of communities of Trichoderma and Fusarium (P < 0.05). The effects of increasing Cu could be seen in both medic and basal soils for Trichoderma, but only in the basal treatments for soil Fusarium. This was due to very low dispersion in Fusarium community structure in the medic-added treatment (PERMDISP; P < 0.05). The results show the interactive influence of organic matter inputs and heavy metal contamination on size and structure of soil fungal communities. The data show that species selection and replacement is an important mechanism for community adaptation to increasing levels of soil Cu, and this mechanism can be influenced by addition of resources to the soil. 相似文献
4.
Christine Stark Leo M. Condron Alison Stewart Hong J. Di Maureen O’Callaghan 《Biology and Fertility of Soils》2007,43(5):531-540
Because soil biota is influenced by a number of factors, including land use and management techniques, changing management
practices could have significant effects on the soil microbial properties and processes. An experiment was conducted to investigate
differences in soil microbiological properties caused by long- and short-term management practices. Intact monolith lysimeters
(0.2 m2 surface area) were taken from two sites of the same soil type that had been under long-term organic or conventional crop
management and were then subjected to the same 2.5-year crop rotation [winter barley (Hordeum vulgare L.), maize (Zea mais L.), lupin (Lupinus angustifolius L.), and rape (Brassica napus L. ssp. oleifera)] and two fertilizer regimes (following common organic and conventional practices). Soil samples were taken after crop harvest
and analyzed for microbial biomass C and N, microbial activity (fluorescein diacetate hydrolysis, arginine deaminase activity,
and dehydrogenase activity), and total C and N. The incorporation of the green manure stimulated growth and activity of the
microbial communities in soils of both management histories. Soil microbial properties did not show any differences between
organically and conventionally fertilized soils, indicating that crop rotation and plant type had a larger influence on the
microbial biomass and enzyme activities than fertilization. Initial differences in microbial biomass declined, while the effects
of farm management history were still evident in enzyme activities and total C and N. Links between enzyme activities and
microbial biomass C varied depending on treatment, indicating differences in microbial community composition. 相似文献
5.
Muller JD Wilks CR O'Riley KJ Condron RJ Bull R Mateczun A 《Australian veterinary journal》2004,82(4):220-222
OBJECTIVE: To evaluate the specificity of an immunochromatographic test (ICT) for anthrax in cattle. DESIGN: A comparison of an ICT with blood smear and culture in uninfected cattle. PROCEDURE: Two hundred and forty blood samples were collected from dead cattle at two knackeries within Victoria and tested on-site with an ICT for the detection of protective antigen (PA) of Bacillus anthracis. Blood smears were prepared on-site and blood samples transported to the laboratory for aerobic and anaerobic culture. The results of the ICT were compared with blood smear and culture. Animals were regarded as not infected with B anthracis if the organism was not detected in a stained blood smear or on culture. Ten healthy yearling cattle were vaccinated with live spore anthrax vaccine and blood samples collected on days 0 to 7 and day 15 were tested in the ICT for the presence of PA. RESULTS: All blood samples from the 240 knackery cattle were ICT, smear and culture negative. All blood samples from the 10 vaccinated cattle were ICT negative. CONCLUSION: The ICT is a test with high specificity in cattle (98.5 to 100%; 95% CI) and recent vaccination of cattle does not give rise to positive reactions. 相似文献
6.
Kai S. J. Lewis Amanda Black Leo M. Condron Nick W. Waipara Peter Scott Nari Williams Maureen O&#x;Callaghan 《Forest Pathology》2019,49(2)
Phytophthora agathidicida is the accepted causal agent of dieback in remnant stands of long‐lived indigenous New Zealand kauri (Agathis australis) and poses a significant threat to the long‐term survival of this species. Little is known about the effect of key soil physicochemical characteristics on the growth of P. agathidicida. In this study, we investigated the growth of P. agathidicida in soils collected from adjacent areas under original kauri forest, short rotation pine (Pinus radiata) plantation forest and grazed pastures. A growth response assay was used to quantify asexual (sporangia) and sexual (oospore) spore counts over 8 days in soils sampled from each land‐use. Significantly higher numbers of sporangia (p < 0.001) and oospores (p < 0.01) were found in pasture and pine forest soil within 2 days of the growth assay trials, suggesting these soils may favour asexual/sexual reproduction in the early stages of P. agathidicida establishment compared to kauri forest soils. Additionally, oospore production significantly increased over 8 days in pine forest soil, suggesting that with an increase in inoculum loads, these soils potentially act as pathogen reservoirs. The soil physicochemical properties (e.g., pH, C and N, phosphorus content and electrical conductivity) investigated in this study did not significantly correspond to spore count data between land‐uses, suggesting that differences in growth response are driven by other edaphic factors not explored in the present study. 相似文献
7.
Effect of supplemental β‐carotene compared to retinyl palmitate on fatty acid profile and expression of mRNA from genes involved in vitamin A metabolism in beef feedlot cattle 
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下载免费PDF全文 Kaitlin N. Condron Jolena N. Waddell Matt C. Claeys Ronald P. Lemenager Jon P. Schoonmaker 《Animal Science Journal》2017,88(9):1380-1387
To examine the effects of dietary β‐carotene (βC) or retinyl palmitate (RP) on fatty acid (FA) profile and mRNA expression, samples were collected from 24 Angus‐cross calves that were allotted to four treatments consisting of RP supplemented at 2200 IU/kg, and synthetic β‐carotene (SβC) supplemented at one, five or 10 times RP. Longissimus muscle (LM) cis‐9, trans‐11 conjugated linoleic acid was greater in RP compared to SβC1X (P = 0.04). The polyunsaturated:saturated FA increased linearly (P = 0.04) in the LM as dietary SβC increased. Expression of βC oxygenase 2 (βCO2), an enzyme that cleaves β‐carotene, was greater in the LM for SβC1X compared to RP and decreased linearly as SβC increased (P ≤ 0.02). Peroxisome proliferator activated receptor γ (PPARγ) expression in the LM increased in SβC1X compared to RP (P = 0.03); however, PPARγ and retinoic acid X receptor α (RXRα) expression decreased linearly (P = 0.02) in the LM with increasing SβC. Retinoic acid receptor α (RARα) expression tended (P = 0.10) to decrease linearly in the LM with increased SβC. In conclusion, SβC supplementation increased mRNA expression of some lipogenic genes in the LM, but increasing dietary SβC inhibited their expression and tended to increase polyunsaturated FA. 相似文献
8.
L. M. Condron D. W. Hopkins E. G. Gregorich A. Black S. A. Wakelin 《European Journal of Soil Science》2014,65(5):741-750
Irrigation of grazed pasture significantly increases plant and animal production, which may in turn increase soil organic carbon (SOC), depending on the balance between primary production and below‐ground allocation of C on the one hand, and the decomposition and export of C from the soil on the other. To evaluate the effect of irrigation on SOC we sampled a grazed pasture field experiment maintained under different irrigation treatments for 62 years. The dry‐land treatment in this experiment only received rainfall at an average of 740 mm year?1. The 10 and 20% irrigation treatments involved application of 100 mm of irrigation when the soil reached 10 and 20% gravimetric moisture content, respectively. The 10 and 20% irrigation treatments received average total annual irrigation inputs of 260 and 770 mm year?1, respectively. The 10 and 20% irrigation treatments increased pasture production by 44 and 74%, respectively, compared with that from the dry‐land. Analysis of soils taken to 1‐m depth revealed that amounts of SOC were not significantly different between the dry‐land (125.5 Mg ha?1) and 10% irrigation (117.8 Mg ha?1) treatments, but these were significantly greater than the 20% irrigation treatment (93.0 Mg ha?1). At 50–100 cm, SOC was also less (34%) for the 20% irrigation treatment than for the 10% irrigation treatment. The relative quantities of carbon (C) and nitrogen (N) in the light fraction (LF) at all soil depths decreased successively from dry‐land to the 20% irrigation treatment, suggesting that wetter soil conditions accelerated decomposition of the LF fraction, a comparatively labile SOC fraction. The C‐to‐N ratio of the bulk soil was also less for the 20% irrigation treatment, indicating more decomposed SOM in the irrigated than in the dry‐land treatment. There were no significant differences in the microbial biomass between the three different irrigation treatments, but the respiration rate (CO2 production) of soil organisms in the 20% irrigation treatment was consistently greater than in the other two treatments. It was concluded that large increases in plant productivity as a result of irrigation had either no effect or significantly reduced SOC stocks under grazed pasture. The reduced SOC content observed in the 20% irrigation treatment was attributed to a combination of increased C losses in animal products and drainage associated with greater stocking, together with accelerated decomposition of organic C resulting from elevated soil moisture maintained throughout the growing season. 相似文献
9.
Phosphorus (P) losses from intensively farmed dairy pastures can impair surface water quality. One of the first steps in mitigating this loss is to determine where in a field the potential for P loss is greatest. This study compared P export in overland flow from grazed pasture with areas that receive elevated P inputs and stock traffic (e.g. gateway, water trough, stream crossing and cattle lane). Intact soil blocks were removed, simulated rainfall applied and overland flow analysed for P fractions and suspended sediment (SS). Soil bulk density, hydraulic conductivity, porosity, Olsen P and water soluble P were also measured. P loss from the sites was in the order: trough > crossing > gateway > pasture. Total P losses from the trough averaged 4.20 mg P/m2 while the pasture exported 0.78 mg P/m2 . In addition, runoff from lane soil was measured with total P averaging 5.98 mg P/m2 , however the method used was different from the other soils. Using stepwise linear regression, Olsen P or H2 O-P, % bare ground and % saturation were the most commonly occurring variables to predict P loss among the sites. This suggests that locating and minimizing the size of these areas in fields has the potential to significantly decrease P loss to surface waters. 相似文献
10.
F. Curran Cournane R. W. Mcdowell R. P. Littlejohn D. J. Houlbrooke L. M. Condron 《Soil Use and Management》2011,27(3):376-384
Agriculture is a major source of phosphorus (P) and suspended sediment (SS) losses to aquatic ecosystems promoting eutrophication. Mechanical soil loosening equipments such as topsoil looseners or aerators have been reported to improve the physical quality and infiltration of soils susceptible to livestock damage resulting from treading. We hypothesized that soil aeration would significantly decrease the volume of surface runoff and consequent losses of P and SS compared with non‐aerated soil (control) in cattle‐grazed pasture on a poorly structured silt‐loam soil. Hydrologically isolated plots (2 m long × 1 m wide × 0.15 m deep) were installed in aerated and control plots to collect surface runoff following irrigation or rainfall and analysed for P and SS losses for 1 year. Soil physical properties [% macroporosity, bulk density, saturated hydraulic conductivity (Ksat) and unsaturated hydraulic conductivity (Kunsat at ?1kPa)] were measured in the aerated and control treatments and taken before each irrigation event (n = 12). Six months after mechanical aeration was employed, but before cattle grazing commenced, no significant differences in soil physical quality were found between aerated and control treatments, with the exception of a minor increase in Kunsat for the control plots. This lack of treatment difference continued after grazing and was largely attributed to the re‐settling of the poorly structured and dispersive soil. Flow‐weighted mean concentrations and annual loads of dissolved reactive P (DRP) on the mechanically aerated soil (2.24 kg DRP/ha) were approximately double those from the control treatment (1.20 kg DRP/ha). However, no significant differences were observed between treatments for surface runoff volumes and losses of total P and total SS, which may reflect the similar soil physical conditions exhibited between treatments throughout most of the trial. As observed elsewhere, time (days) since grazing or fertilizer application was found to influence P and/or SS losses. We conclude that aeration did not decrease P and SS losses. Any changes in soil physical properties such as macroporosity were short‐lived and therefore unlikely to influence surface runoff and subsequent P and SS losses for this soil type. 相似文献