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An experiment was conducted during May to December 2002 to determine growth performance, the highest economic return and suitable species composition in the polyculture of Thai pangus (Pangasius hypophthalmus) with carps (catla, Catla catla and rohu, Labeo rohita) and freshwater giant prawn (Macrobrachium rosenbergii) using low‐cost formulated feed. Three treatments (T1, T2 and T3) were conducted with three replications. The treatment T1 was designed as a monoculture of pangus with a stocking density of 17 500 individual ha?1. The other two treatments (T2 and T3) were designed as polyculture and stocked with pangus, catla, rohu and prawn with densities of 10 000, 2500, 5000, 3750 ha?1; and 10 000, 5000, 2500, 3750 ha?1 in T2 and T3 respectively. The net weight gain and production of pangus were significantly different (P>0.05) between monoculture and polyculture but were not different within the two polyculture systems. The production of catla and rohu were significantly different (P>0.05) in both treatments where prawn was not. Though the gross production (8.53 ton ha?1) was significantly (P>0.05) higher in T1, the higher gross net profit (Tk 154 201 ha?1) was in T2. Thus, the polyculture of pangus is more profitable than its monoculture and the species composition in T2 is more suitable than other composition.  相似文献   
2.

Routine monitoring for subclinical infection is one of the key mastitis control approaches. However, the accuracy of the most commonly used screening tests has not yet been established. The aim of the present study was therefore to evaluate the accuracy of three screening tests, namely California mastitis test (CMT), white side test (WST), and surf field mastitis test (SFMT) for the screening of subclinical caprine mastitis. A cross-sectional study based on 484 randomly collected milk (242 goats) samples from three districts of Bangladesh was conducted for the screening of subclinical mastitis by the aforementioned tests. The Bayesian latent class model was implemented in WinBUGS to estimate the tests’ characteristics and true prevalence of subclinical mastitis. The Bayesian posterior estimates of sensitivities with a 95% credible intervals (CrIs) were 98.60% (95.18–99.95%), 98.28% (94.56–99.92%), and 89.98% (83.39–95.03%), and specificities with 95% CrIs were 99.19% (98.11–99.96%), 99.27% (97.34–99.98%), and 99.28% (97.35–99.98%), respectively for CMT, WST, and SFMT. The true prevalence of subclinical caprine mastitis was estimated to be 43.49% (95% CrI 37.46–48.98%). The positive predictive values (PPV) of the three tests were similar. The serial and parallel interpretation of any test pairs increased the PPV and negative predictive value respectively close to 100%. Based on the simplicity, cost and performance as well WST and SFMT simultaneously could be recommended for the screening of caprine subclinical mastitis in Bangladesh.

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3.
The purpose of the study was to identify the potential risk factors for subclinical mastitis (SCM) in lactating dairy cows in Bangladesh. A cross-sectional study was carried out on randomly selected 212 smallholder dairy farms of Sadar upazilas of Rangpur, Mymensingh, and Satkhira districts of Bangladesh during January to October 2011. The direct interview using a structured questionnaire and physical examination of the cows were done to collect data on 15 variables. Milk samples collected from study cows were subjected to California Mastitis Test (CMT). The diagnosis of SCM was based on the results of CMT and physical examination of udder and milk. The bivariable followed by multivariable analysis was done using SPSS 17.0. Of the total cows examined, 20.2 % had subclinical mastitis. In bivariable analysis, eight risk factors were identified. However, in the final model of multivariable analysis, four potential risk factors were identified. These were history of previous clinical mastitis (odds ratio (OR) 10.51, p?<?0.001), pendulous type of udder (OR 2.26, p?=?0.008), no grass feeding (OR 1.84, p?=?0.039), and body condition score (BCS) 2.5 or less (OR 7.25, p?=?0.054). Four different factors were significantly associated with the occurrence of subclinical mastitis, which need to be considered in the control of the disease. However, particular emphasis should be given on grass feeding and BCS because these traits can be modified or improved to allow prevention of SCM.  相似文献   
4.
The effects of ditch size on growth and production of mono‐sex tilapia, Oreochromis niloticus in rain fed concurrent rice–fish system were technically and economically evaluated for a period of 4 months. Three different ditch sizes were tried: 5%, 10% and 15% of the total cultivable rice field. The fish fingerlings stocking density (5000 ha?1) and management practices were similar in all plots. The water temperature, dissolve oxygen, pH, Secchi disc visibility, ortho‐phosphate, ammonia nitrogen and alkalinity were found to be in the range of 31.5–31.9°C, 5.10–5.27 mg L?1, 7.56–7.62, 34.81–35.41 cm, 0.88–0.96 mg L?1, 0.014–0.021 mg L?1 and 66.23–69.76 mg L?1, respectively, and all the values were found suitable for tilapia fish farming. Sediment organic matter, available nitrogen and phosphorous were increased significantly (P < 0.05) in all plots after cultivating the fish. Larger ditch size (15% of the total land area) resulted in significantly (P < 0.05) higher specific growth rate, survival and fish production compared with the smaller (5%) and medium (10%) ditch sizes. However, significantly (P < 0.05) higher net income and benefit–cost ratio were obtained in medium ditch size with the values of 2.6% and 3.6% higher than the smaller and larger ditch sizes respectively. It is concluded that rice–fish farming in a rain fed ecosystem of Bangladesh with medium ditch size and stocking density of 5000 ha?1 mono‐sex tilapia can achieve better economic return.  相似文献   
5.
Harnessing the rhizospheric microbiome, including phosphorus mineralizing bacteria (PMB), is a promising technique for maintaining sustainability and productivity in intensive agricultural systems. However, it is unclear as to which beneficial taxonomic group populations in the rhizosphere are potentially associated with the changes in soil microbiomes shifted by fertilization regimes. Herein, we analyzed the diversity and community structure of total bacteria and PMB in the rhizosphere of maize (Zea mays L.) grown in soils under 25 years of four fertilization regimes (compost, biocompost, chemical, or non-fertilized) via selective culture and Illumina sequencing of the 16S rRNA genes. Plant development explained more variations (29 and 13%, respectively) in the composition of total bacteria and PMB in the rhizosphere of maize than the different fertilization regimes. Among those genera enriched in the rhizosphere of maize, the relative abundances of Oceanobacillus, Bacillus, Achromobacter, Ensifer, Paracoccus, Ramlibacter, and Luteimonas were positively correlated with those in the bulk soil. The relative abundance of Paracoccus was significantly higher in soils fertilized by compost or biocompost than the other soils. Similar results were also observed for PMB affiliated with Ensifer, Bacillus, and Streptomyces. Although plant development was the major factor in shaping the rhizospheric microbiome of maize, fertilization regimes might have modified beneficial rhizospheric microbial taxa such as Bacillus and Ensifer.  相似文献   
6.
A cross-sectional study was carried out to estimate the true prevalence of Brucella spp. and identify allied risk factors/indicators associated with brucellosis in the Dinajpur and Mymensingh districts of Bangladesh. A total 320 stratified random blood samples were collected and tested in parallel for Brucella antibodies using Rose Bengal (RBT), slow agglutination (SAT), and indirect and competitive ELISA. In addition, a structured questionnaire was administered to each household herd owner to gather information regarding potential risk factors. Both univariate and multivariate logistic regression analyses were used to identify potential risk factors or indicators at animal level. A Bayesian approach was used to estimate the true prevalence of brucellosis along with the test performances (Se and Sp). The estimated animal level true prevalence in cattle was 9.70 % (95 % CPI 5.0–16 %) and in goat 6.3 % (95 % CPI 2.8–11.0 %). The highest sensitivity was achieved by SAT ranges from 69.6 to 78.9 %, and iELISA was found to be more specific (97.4 to 98.8 %) in comparison with other tests. On the other hand, a significant level of (P?<?0.05) Brucella seropositivity was found in cattle that breed naturally compared with those that undergo artificial insemination. In goats, exotic breeds were significantly associated (P?<?0.05) with Brucella seroprevalence compared with indigenous breeds. Goats with a previous records of abortion and/or retained placenta were also found to have significant levels (P?<?0.05). Cows with previous abortion records showed higher odds (18 times) of being seropositive. None of the evaluated tests can be recommended to apply alone for the diagnosis of bovine and caprine brucellosis.  相似文献   
7.
For this study, characteristics and trends of the chemical constituents in bulk precipitation and streamwater were observed in a small mountainous watershed on the Shikoku Island of Japan, which covered an area of 27.4 hectares. Bulk precipitation and streamwater chemistry data spans from May 1997 to October 2004, and January 1996 to October 2004, respectively. The data were tested for two types of trends: (1) a monotonic trend to determine if concentrations of the chemical constituents were generally decreasing, increasing, or stable during the study period, and (2) a step trend to determine if a change occurred following the December 1999-January 2000 forest thinning. Both parametric and non-parametric statistical analyses were carried out in this study. Although the study area is only 35 km away from the Pacific Ocean, bulk precipitation chemistry was also influenced by terrestrial sources to a large extent. Streamwater chemistry was influenced by bedrock weathering, which was dominated by Ca2+ and HCO3?, and was not strongly related top recipitation chemistry.Non?parametric Seasonal Kendall Test(SKT)showedadeceasingtr end of Ca 2+ and anincreasing tr end of K + in bulk precipitation.Despite the decreasing trend of Mg 2+, an increasing trend of pH was found in the stream water.Non?paramet ric Mann?Whit ney?Wilcoxon Rank Sum test showed statistically sign if icantin creases of NO 3? and Ca 2+ in stream water followed by a moderate thinning operation.  相似文献   
8.
This paper reports the fabrication, characterization and simulation of electrospun polyacrylonitrile (PAN) nanofibers into pre-impregnated (prepreg) carbon fiber composites for different industrial applications. The electrospun PAN nanofibers were stabilized in air at 270 °C for one hour and then carbonized at 950 °C in an inert atmosphere (argon) for another hour before placing on the prepreg composites as top layers. The prepreg carbon fibers and carbonized PAN nanofibers were cured together following the prepreg composite curing cycles. Energy dispersive X-ray spectroscopy (EDX) was carried out to investigate the chemical compositions and elemental distribution of the carbonized PAN nanofibers. The EDX results revealed that the carbon weight % of approximately 66 (atomic % 72) was achieved in the PAN-derived carbon nanofibers along with nitrogen and lower amounts of nickel, oxygen and other impurities. Thermomechanical analysis (TMA) exhibited the glass transition regions in the prepreg nanocomposites and the significant dependence of coefficient of thermal expansion on the fiber directions. The highest value of coefficient of thermal expansion was observed in the temperature range of 118-139 °C (7.5×10-8 1/°C) for 0 degree nanocomposite scheme. The highest value of coefficient of thermal expansion was observed in the temperature range of 50-80 °C (37.5×10-6 1/°C) for 90 degree nanocomposite scheme. The test results were simulated using ANSYS software. The test results may be useful for the development of structural health monitoring of various composite materials for aircraft and wind turbine applications.  相似文献   
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