The timing of inorganic fertilization of sunfish ponds

Fertilization with diammonium phosphate (20 kg/ha per application) was initiated at different dates in each of four treatments replicated three times in 0.04-ha ponds. Although there were some differences in averages of total and filtrable orthophosphate concentrations and phytoplankton abundance among treatments (P < 0.05), sunfish production was not influenced by the timing of fertilization (P > 0.05). Phytoplankton blooms did not develop in any of the treatments until late spring or early summer. The failure of phytoplankton to respond to fertilization in late winter and early spring was apparently related to low water temperature and competition by macrophytes. In larger, deeper ponds (> 0.5 ha), inorganic fertilization will cause phytoplankton blooms in early spring even when water temperatures are low.     

Determination of the phosphorus fertilization rate for bluegill ponds using regression analysis

Pond fertilization studies usually are restricted by availability of ponds forcing researchers to limit treatments to maintain adequate replicates for statistical analysis. Data from a wide range of fertilizer rates applied over a single season in un‐replicated ponds were treated using regression analysis to establish the optimum phosphorus application rate for bluegill (Lepomis macrochirus) ponds. The response to phosphorus fertilization conformed to a saturation model (R²=0.92). Bluegill production increased with greater fertilization rate up to 3 kg P₂O₅ ha^?1, but production was similar (501–558 kg ha^?1) at rates of 3–7 kg P₂O₅ ha^?1. The observation that 3 kg P₂O₅ ha^?1 per application was adequate phosphorus fertilization for bluegill ponds with sufficient nitrogen agrees closely with the usual recommendation of 4 kg P₂O₅ ha^?1 per application. Results of this research also revealed that nutrient assessment in bluegill ponds can be based on total nitrogen and total phosphorus analyses, and Secchi disk visibility may be used as an index of plankton abundance.     

Chemical Characteristics of Bottom Soils from Freshwater and Brackishwater Aquaculture Ponds

Soil chemical analyses were conducted on samples from 358 freshwater fish ponds and 346 brackishwater shrimp ponds. Freshwater ponds were located in Honduras, Rwanda, Bhutan, and the United States. Ponds in the United States were in Alabama, Georgia, Mississippi, Florida, and South Carolina. Brackishwater ponds were in Thailand, Ecuador, Philippines, and Venezuela. Soils of freshwater and brackishwater ponds did not differ greatly in average concentrations and concentration ranges for carbon, nitrogen, calcium, and pH. Concentrations of copper and barium tended to be higher in freshwater soils than in brackishwater ones. All other measured chemical constitutents tended to be more abundant in the soils of brackishwater ponds than in those of freshwater ponds. For the most part, ranges of pond soil chemical properties were similar to those of terrestrial soils, with freshwater pond soils resembling terrestrial soils from humid areas and brackishwater soils being similar in many respects to soils of arid regions. However, some brackishwater pond soils were highly acidic, acid-sulfate soils. Data were arranged into concentration categories (very low, low, medium, high, and very high) to facilitate comparisons of the present data set with other data on soil chemical properties for aquaculture ponds. All ponds included in the present study were used for aquaculture, showing that it is possible to rear fish and shrimp across an extremely wide range of soil chemical properties.     

重组卡介苗感染树突细胞的研究

在体内外试验中 ,树突细胞 (DC)均能摄取表达大肠杆菌麦芽糖结合蛋白 (MalE)的重组卡介苗 (rBCG·MalE)。应用流式细胞术测得荧光标记的rBCG·MalE在体内感染DC的水平在 1 % 2 % ,与感染巨噬细胞 (MΦ)的水平相当。体外抗原提呈试验结果显示 ,DC和MΦ能吞噬、加工rBCG·MalE并向T细胞杂交瘤FBU·B1 1提呈MalE蛋白抗原表位 ,而在体内试验中 ,从rBCG·MalE免疫小鼠脾脏中纯化的DC ,可检测到MalE表位MHCⅡ复合物 ,而纯化的MΦs却测不到。这表明DC在起始抗分枝杆菌的免疫保护中发挥关键作用。     

Ionic Supplementation of Pond Waters for Inland Culture of Marine Shrimp

Saline well water used to fill ponds for inland culture of marine shrimp in Alabama often have low concentrations of potassium and magnesium. In 2002, pond waters on a shrimp farm were treated with enough muriate of potash and potassium-magnesium sulfate (K-Mag) to increase potassium concentration from 6.2 mg/L to about 40 mg/L and magnesium concentrations from 4.6 mg/L to about 20 mg/L. Salinity in ponds averaged 2.6 ppt at the time of mineral salt additions. The concentrations of potassium and magnesium remained fairly constant throughout the growing season without further applications of salts, and salinity increased to about 4 ppt mainly as a result of concentration through evaporation. Survival and production on the farm averaged 19% and 595 kg/ha, respectively, in 2001. In 2002, average survival improved to 67% and average production was 4,068 kg/ha. Ponds were stocked at similar rates and managed by similar procedures both years. Magnesium concentration was very low related to the concentration expected in normal seawater diluted to the same salinity as the pond water, while potassium was near the expected concentration. Thus, increased potassium concentration is thought to have influenced production much more than did the increase in magnesium concentration. K-Mag does not dissolve as readily as muriate of potash. Thus, K-Mag should not be dumped in shallow water areas of ponds to dissolve as can be done with muriate of potash. It should be broadcast over the pond surface, predissolved and splashed over the pond surface, or placed in porous bags suspended in front of aerators. Although a single application of mineral salts was effective, 2002 was a dry year. On a wet year, ions may be diluted or flushed out in overflow and more than one treatment with mineral salts might be necessary during the growing season.     

Original surgical treatment of thoracolumbar subarachnoid cysts in six chondrodystrophic dogs

Background

Subarachnoid cysts are rare conditions in veterinary medicine, associated with spinal cord dysfunction. Most of the 100 cases of subarachnoid cysts described since the first report in 1968 were apparently not true cysts. Reported cysts are usually situated in the cervical area and occur in predisposed breeds such as the Rottweiler. The purpose of this retrospective study, from May 2003 to April 2012, was to describe the distinctive features of thoracolumbar spinal subarachnoid cysts, together with their surgical treatment and outcome in 6 chondrodystrophic dogs.

Results

Five Pugs and 1 French Bulldog were examined. Images suggestive of a subarachnoid cyst were obtained by myelography (2/6) and computed tomography myelography (4/6), and associated disc herniation was observed in 3/6 dogs. A hemilaminectomy was performed. The protruding disc eventually found in 5/6 dogs was treated by lateral corpectomy. The ventral leptomeningeal adhesions observed in all dogs after durotomy were dissected. No or only mild post-operative neurological degradation was observed. Follow-up studies (7 months to 4 years) indicated good outcome and no recurrence.

Conclusions

All the thoracolumbar subarachnoid cysts described in these 6 chondrodystrophic dogs were associated with leptomeningeal adhesions. Good results seemed to be obtained by dissecting and removing these adhesions. A protruding disc, found here in 5/6 dogs, needs to be ruled out and can be treated by lateral corpectomy.     

Mercury in Northern Québec: Role of the Mercury Agreement and Status of Research and Monitoring

In order to determine the nature and extent of the problem caused by the presence of mercury in the environment of the James Bay territory a Mercury Agreement was signed in 1986 jointly by the Crees, the Govemment of Québec and Hydro-Québec. The objectives were to minimize potential hazards to human health arising from the presence of mercury in the environment, to alleviate negative impacts on the Crees, their way of life and their harvesting activities and to provide for remedial measures. Monitoring of mercury concentrations in fish show that, 15 years after impounding of La Grande-2 reservoir, the concentrations remain higher in reservoirs than in natural lakes but they are now decreasing in both predatory (Northern pike) and non-predatory (Whitefish) fishes. Monitoring of the mercury exposure among the Crees showed that concentrations in hair have decreased and are now stabilized, for most of the population, to concentrations that do not present a health risk. This decrease may be attributed to a reduction in fish consumption and/or a possible switch of the diet towards non-piscivorous fish, less contaminated by mercury.     

Soil organic matter quality as influenced by tillage,lime, and phosphorus

In Eastern Canada, cereal yields are often restricted by soil acidity and low fertility. Continuous cereal production can also lead to soil structural degradation. The addition of lime and fertilizers and the adoption of conversation tillage practices are proposed solutions which may have a positive impact on soil quality. The objective of the present work was to assess the impact of 3 years of different tillage practices and P additions, and of a single lime addition on organic C and total N, microbial biomass C, and on N mineralization at the surface layer (0–7.5 cm) of a Courval sandy clay loam (Humic Gleysol). The easily mineralizable N, total amount of N mineralized in 22.1 weeks, the rate of N mineralization, and microbial biomass C were significantly greater in the minimum tillage than in the moldboard plow treatment. Chisel plow treatment showed intermediate values. The ratios of potentially mineralizable N and of easily mineralizable to total soil N were also significantly larger under minimum tillage and chisel plowing than under moldboard plowing. The lime and P treatments had no significant effect on the measured soil quality parameters. The total amount of N mineralized per unit of biomass C decreased as the tillage intensity increased, suggesting a decrease in the efficiency of the biomass in transforming organic N into potentially plant-available forms and thus a loss in soil organic matter quality. The results of this study indicate that conservation tillage practices such as rototilling and chisel plowing are efficient ways of maintaining soil organic matter quality when old pastures are brought back into cultivation.     

Application of agro-ecological concepts and hierarchy theory in the design of databases for spatial and temporal characterisation of land and soil

A hierarchial system for integrating information on soil, climate, landscape and land use at various scales, is discussed. A series of nested data bases at various scales (1:5 million and larger) are prepared, according to the concepts of agro-ecological stratification in combination with the tenets of Hierarchy Theory. Each polygon at each scale is treated as a unique area with its own environmental envelope of integrated information. Transposition between scales and the scientific integrity of the data is accomplished through the nested databases, and by carefully matching the “grain” of the data to the scale of each database.

The nested databases are “matched” with a collection of crop growth models and other procedures of data analyses, each of which is specific to a general scale of application, and compatible to one of the available databases. The crop growth models are arranged in increasing detail, as reflected in the structure of the subroutines and time steps, and describe a variety of purposes from estimating yield potential to defining yield variability and production risk. The system is supported by a geographic information system.     

Sur une nouvelle methode de dosage du dioxyde d'azote present dans les atmospheres polluees,derivee de la methode de Griess-Saltzmann

This paper discusses a procedure involving absorption of NO₂ on triethanolamine impregnated-papers according to a recent study of Levaggi, Siu and Feldstein. The used solid surfaces are Millipore filters, first impregnated by stirring them in a solution containing triethanolamine, glycerol and acetone before drying in an oven. Storage is made in a closed glass container. For sampling, check air flow rate to be about 30 l h^?1 through filters. The sampling time depends on the actual concentration. Samples are then analyzed in a laboratory under Saltzman's colorimetric reaction. The composition of the reagents is slightly modificated (acetic acid is replaced by phosphoric acid to obtain pH 1). Color development needs 30 min and then absorbance is compared with a standardization curve built from dilute solutions of Na NO₂. Absorption efficiencies of over 95% are attained with two impregnated filters in a filter holder and at about 301 h^?1 flow rate. Stability of filters after sampling is evaluated at 2 or 3 weeks, so it is possible to store several filters before sending them (for example by mail) to the laboratory for analysis. The stoichiometric factor depends on the weight (expressed in μg) of NO₂ collected on the filters and varies between 1.0 and 0.84. To measure NO, oxidation into NO₂ is first required, for example with an O₃ lamp.