Prevalence of <Emphasis Type="Italic">Toxoplasma gondii</Emphasis> and <Emphasis Type="Italic">Neospora caninum</Emphasis> infections in sheep from Federal District,central region of Brazil

Serum samples from 1028 sheep were collected from 32 herds within Federal District, in the central region of Brazil. The samples were examined by indirect fluorescent antibody test (IFAT) using sera diluted 1:64 and 1:50 as cut-off values for the detection of antibodies against Toxoplasma gondii and Neospora caninum, respectively. The observed prevalence for T. gondii infection was 38.22% (26.81%<CI 0.95<49.62%), and the titers ranged from 64 to 65536. The observed prevalence for N. caninum infection was 8.81% (7.08%<CI 0.95<10.53%). The titers ranged from 50 to 51200. The reactant sera to both pathogens corresponded to 4.67% of the samples. The risk factors were not determined because of the absence of negative herds for T. gondii and the high proportion of positive herds for N. caninum (87.50%). The prevalence for T. gondii infection was significantly higher among males than in females. The present work is the first report on seroprevalence of T. gondii and N. caninum in sheep from Federal District and shows that infection by both parasites is widespread in the ovine population from this region.     

Influence of Plant Residues after Steam-Treatment with High Temperature and Pressure on Soil Microbial Biomass C and N, Water-Soluble C and N, and pH

Steam-treated grass trimmings (GrT), and wooden chips of pine (PnT) and walnut branches (WnT) or non-treated grass trimmings (GrNoT) and wooden chips of pine (PnNoT) and walnut branches (WnNoT) were mixed with soil (S) and then incubated for 10 weeks to measure microbial biomass C (MBC) and N (MBN), water-soluble C (WSC) and N (WSN), and soil pH. The results showed that there were a larger amount of MBC and WSC in steam-treated samples, principally in early period. It was probably due to the steam-treatment facilitating solubilization of organic C that served with substrate for microbial biomass. In grass trimming, the MBN and WSN had differences between treated and non-treated. No such differences in wooden chips was probably because the low total N content in these plants. The higher value of WSN showed in S+GnNoT showed more potential of nitrate pollution. The steam-treatment did not influence on soil pH after 1 week of incubation.     

Evaluation of bulk density of Albaqualf soil under different tillage systems using the volumetric ring and computerized tomography methods

The volumetric ring and the computerized tomography (CT) techniques were applied to study soil bulk density, in order to understand the compaction of an Albaqualf soil (Planosol) of the Rio Grande do Sul State, Southern Brazil (latitude 31°52′00″S and Longitude 52°21′24″W). Among six different tillage systems and crop rotations the greatest soil bulk density was measured for the continuous irrigated rice crop system and the lowest for the no-tillage treatment under rye grass straw. The CT method enabled the measurement of bulk density variations in the soil profile and indicated critical zones not observed by the volumetric ring method that measures only the mean sample soil bulk densities. A meaningful correlation between soil bulk densities measured by both methods was found, although the CT method presented more reliable results in comparison to the volumetric ring method. A 3% variation in bulk density was observed due to method intrinsic errors, probably also correlated to different samples sizes.     

Study of Pyrene Adsorption on Two Brazilian Soils

This study investigated pyrene adsorption on two contrasting Brazilian soils: a Kandiudult and a Vertisol. It was found that the time taken to reach thermodynamic equilibrium depended on the soil type. The curves for different pyrene-to-soil mass ratios for Vertisol soil showed significant differences. This is probably related to the presence of 2:1 clays that may increase the adsorption of pyrene due to the resulting interlamellar space. The adsorption of pyrene on the Kandiudult showed, in general, good agreement with the Langmuir isotherm. In the case of the Vertisol, there was good agreement with the linear isotherm. The kinetic model that best explains the adsorption in Kandiudult was the pseudo second-order model. For the Vertisol, the Morris Weber model best explains the behavior of pyrene.     

Effect of Water Stress in Maize Crop Production and Nitrogen Fertilizer Fate

ABSTRACT

Maize production is affected by water and nitrogen (N) deficit either separately or joined, but this fact is not completely defined. The aim was to evaluate the fate of N in maize fertilized and subjected to water stress in controlled conditions. A greenhouse experiment was carried out at the University of Buenos Aires campus. The design was a 2 × 2 factorial with four replications. The factors were N: 70 and 140 kg N ha^?1 as labeled urea (¹⁵N), and water: 100% or 50% of the potential evapotranspiration. The harvest of aerial and root biomass was carried out at R1 stage. Nitrogen in plants, soils nitrate, ammonia volatilization, and ¹⁵N percentage were determined. Obtained results only partially agree with previous research. Water stress depressed aerial biomass production independently of N doses. When water was limiting, the uptake of N from fertilizer was independent of N. When water was not limiting, N uptake increased with the higher N doses. Volatilization losses were 3.7 to 7.8% of N applied as fertilizer. Plant N recovers was around 45% of the N applied, except in treatment water stressed with high N rate (19%). Nitrate-N from the fertilizer in the soil at harvest and accumulated N from the fertilizer in plant were lineally related (r² = 0.54; p < 0.001). Important destinations of N were accumulation in plant, volatilization and incorporation into soil organic matter. However, residual nitrate was a main fate in heavily fertilized and water deficit treatment. This process could lead to the eventual nitrate leaching.     

Flow cytometric immune profiling of specific-pathogen-free chickens before and after infectious challenges

Broilers and layer chickens have been intensively selected for production parameters. This selection has affected immune capacity. Consequently, the fine-tuning of immune responses is becoming important for maximum productivity. Flow cytometry is a recurrent technology used for the immunophenotyping of birds. Studies, however, have focused on the mechanism of specific diseases or have used animals whose immunological condition could be biased-by vaccination or environmental stressors, for example. The aim of this study was to evaluate the immune status of specific-pathogen-free birds across different age ranges to characterize the natural changes that occur over time. Additionally, specific-pathogen-free chickens were challenged with four infectious agents, allowing identification of the subpopulations of peripheral blood immune cells that are consistently altered under various conditions. Several lymphocyte subsets vary naturally with aging, so the interpretation of results using animals of different age ranges must proceed with care. Parameters such as CD8(+)CD28(-), CD8αα(+), CD4(+)CD8(+), and CD8(+)TCRVβ1(+) have been shown to be valuable in understanding immune changes during disease. The use of these data allows a determination of the consistency of cytometric parameters under various conditions, which should ease the interpretation of immunophenotyping and the future application of cytometric analysis in the poultry industry.     

Occurrence of antibodies to Toxoplasma gondii and Lepstospira spp. in manatees (Trichechus inunguis) of the Brazilian Amazon

The presence of Toxoplasma gondii and Leptospira spp. antibodies was investigated in 74 manatees (Trichechus inunguis [Mammalia: Sirenia]) kept in captivity in two rescue units in the northern region of Brazil. Antibodies to T. gondii were detected in 29 (39.2%) of 74 animals by using the modified agglutination test (titer, 1:25). For antibodies against Leptospira spp., sera were diluted 1:50 and tested against 24 strains ofleptospires by microscopic agglutination microtechnique, and positive samples were end titrated. Twenty-three (31.1%) of 74 animals were reactive to four serovars (Patoc 21/23, Castellonis 2/23, Icterohaemorrhagiae 1/23, and Butembo 1/ 23), with titers ranging from 100 to 1,600. This is the first report of antibodies against T. gondii and Leptospira spp. in T. inunguis from the Brazilian Amazon.     

Biomass production and potential water stress increase with planting density in four highly productive clonal Eucalyptus genotypes§

The choice of planting density and tree genotype are basic decisions when establishing a forest stand. Understanding the interaction between planting density and genotype, and their relationship with biomass production and potential water stress, is crucial as forest managers are faced with a changing climate. However, few studies have investigated this relationship, especially in areas with highly productive forests. This study aimed to determine the interaction between biomass production and leaf water potential, as a surrogate of potential water stress, in different clonal Eucalyptus genotypes across a range of planting densities. Four clones (two clones of E. urophylla × E. grandis, one clone of E. urophylla, and one clone of E. grandis × E. camaldulensis) and four planting densities (ranging from 591 to 2 949 trees ha^?1) were evaluated in an experimental stand in south-eastern Brazil. Biomass production was estimated 2.5 years after planting and predawn (ψ_pd) and midday (ψ_md) leaf water potential were measured 2 and 2.5 years after planting, in February (wet season) and August (dry season) in 2014. For all clones, total stand stemwood biomass production increased and leaf water potential decreased with planting density, and their interaction was significant. Thus, wood biomass at tighter spacings was higher but exhibited lower leaf water potentials, resulting in a trade-off between productivity and potential water stress. These are preliminary findings and still need to be supported by more experimental evidence and repetitions. However, in light of the increased frequency of extreme climate events, silvicultural practices that are tailored to the potential productivity of each region and that result in low potential water stress should be considered.