Influence of soil properties on the adsorption-desorption of sulcotrione and its hydrolysis metabolites on various soils

The retention process of sulcotrione and its two hydrolysis products, 1,3-cyclohexanedione (CHD) and 2-chloro-4-methylsulfonylbenzoic acid (CMBA), were studied in four different soils (Belgium, Landes, Perpignan, and Martinique) under laboratory conditions. Adsorption isotherms were well fitted by a Freundlich relationship. The values of K(fa) ranged from 0.4 to 27.0, and the most adsorbed compound was CHD regardless the soil type. Sulcotrione and CMBA exhibited similar retention behaviors. According to adsorption and desorption results, sulcotrione presents a moderate affinity with soil components; however, its leaching capacity needs to be carefully assessed. Clay content seemed to be the most important factor influencing the adsorption capacity of each compound, whereas organic matter and pH had little influence. The soils were classified according to their adsorption capacity in the following decreasing order: Martinique, Belgium, Landes, Perpignan.     

Short-term browsing by roe deer has little effect on survival and growth of sessile oak seedlings

We studied the effect of roe deer (Capreolus capreolus) browsing on the growth and mortality of sessile oak (Quercus petraea) seedlings. First, we measured the height and basal diameter, and counted the number of shoots of the 849 seedlings of an experimental plantation, 60 of which were individually protected by fencing. We then introduced two tame roe deer females every day for three weeks from late May to mid-June. Measurements and counts were repeated after roe deer removal, then once again the following winter. We found no significant effect of browsing on mortality, total height, or basal diameter of the seedlings. However, the browsed seedlings exhibited a lower number of shoots despite regrowth observed after roe deer removal. We propose to use the tolerance of oak to deer browsing to promote natural and inexpensive methods, to protect oak during regeneration, such as the spatial arrangement of plants or the use of slash or surrounding vegetation in favourable environments.     

Topography and crop management are key factors for the development of american leaf spot epidemics on coffee in costa rica

ABSTRACT We monitored the development of American leaf spot of coffee, a disease caused by the gemmiferous fungus Mycena citricolor, in 57 plots in Costa Rica for 1 or 2 years in order to gain a clearer understanding of conditions conducive to the disease and improve its control. During the investigation, characteristics of the coffee trees, crop management, and the environment were recorded. For the analyses, we used partial least-squares regression via the spline functions (PLSS), which is a nonlinear extension to partial least-squares regression (PLS). The fungus developed well in areas located between approximately 1,100 and 1,550 m above sea level. Slopes were conducive to its development, but eastern-facing slopes were less affected than the others, probably because they were more exposed to sunlight, especially in the rainy season. The distance between planting rows, the shade percentage, coffee tree height, the type of shade, and the pruning system explained disease intensity due to their effects on coffee tree shading and, possibly, on the humidity conditions in the plot. Forest trees and fruit trees intercropped with coffee provided particularly propitious conditions. Apparently, fertilization was unfavorable for the disease, probably due to dilution phenomena associated with faster coffee tree growth. Finally, series of wet spells interspersed with dry spells, which were frequent in the middle of the rainy season, were critical for the disease, probably because they affected the production and release of gemmae and their viability. These results could be used to draw up a map of epidemic risks taking topographical factors into account. To reduce those risks and improve chemical control, our results suggested that farmers should space planting rows further apart, maintain light shading in the plantation, and prune their coffee trees.     

Administration of probiotics influences F4 (K88)-positive enterotoxigenic Escherichia coli attachment and intestinal cytokine expression in weaned pigs

ABSTRACT: This study evaluated the effect of the probiotics Pediococcus acidilactici and Saccharomyces cerevisiae boulardii on the intestinal colonization of O149 enterotoxigenic Escherichia coli harbouring the F4 (K88) fimbriae (ETEC F4) and on the expression of ileal cytokines in weaned pigs. At birth, different litters of pigs were randomly assigned to one of the following treatments: 1) control without antibiotics or probiotics (CTRL); 2) reference group in which chlortetracycline and tiamulin were added to weanling feed (ATB); 3) P. acidilactici; 4) S. cerevisiae boulardii; or 5) P. acidilactici + S. cerevisiae boulardii. Probiotics were administered daily (1 × 109 CFU per pig) during the lactation period and after weaning (day 21). At 28 days of age, all pigs were orally challenged with an ETEC F4 strain, and a necropsy was performed 24 h later. Intestinal segments were collected to evaluate bacterial colonization in the small intestine and ileal cytokine expressions. Attachment of ETEC F4 to the intestinal mucosa was significantly reduced in pigs treated with P. acidilactici or S. cerevisiae boulardii in comparison with the ATB group (P = 0.01 and P = 0.03, respectively). In addition, proinflammatory cytokines, such as IL-6, were upregulated in ETEC F4 challenged pigs treated with P. acidilactici alone or in combination with S. cerevisiae boulardii compared with the CTRL group. In conclusion, the administration of P. acidilactici or S. cerevisiae boulardii was effective in reducing ETEC F4 attachment to the ileal mucosa, whereas the presence of P. acidilactici was required to modulate the expression of intestinal inflammatory cytokines in pigs challenged with ETEC F4.     

Survey of Anaplasmataceae bacteria in sheep from Senegal

Purpose

The authors studied the role of bacteria belonging to Anaplasmataceae family as the causes of acute illnesses of sheep in West Africa.

Methods

We examined and sampled 120 febrile sheep in two regions of Senegal for this study. The DNA extracted from these blood samples was tested by PCR using two pairs of primers (groEL-based and 16S rRNA gene-based).

Results

In 52/120 samples, the microscopic examination revealed intraerythrocytic and/or intraphagocytic spherical inclusions. In 48/52 cases, we succeeded in identifying the bacterial agent: in 38 cases, it was Anaplasma ovis; in six cases, it was Ehrlichia ruminantium; in two cases, Anaplasma phagocytophilum; in one case, Anaplasma platys; and in one case, a yet uncultured Anaplasma sp. closely related to A. phagocytophilum.

Conclusions

Our studies demonstrated the great variety of pathogenic bacteria from the Anaplasmataceae family in the blood of clinically ill sheep. A. ovis was identified unexpectedly often. For the first time, A. phagocytophilum was found in sub-Saharan Africa, and its further epidemiology may be now reconsidered. The roles of canine pathogen, A. platys, and yet undescribed Anaplasma sp. “Badiouré” in ovine pathology should be more closely studied.     

Self-thinning dynamics in experimental scallop populations

Self-thinning-related mortality has been encountered in extensively cultured scallop populations. Here we report an experiment aimed at studying actual population dynamics of scallops undergoing self-thinning and develop a model of the process. Scallops were kept in small tanks at various initial population densities. Growth and survival were monitored for 39 months. Two cohorts were monitored (cohorts 1 and 2 were 1 and 2 years old, respectively). Growth was density-dependent in cohort 2. Survivorship was high in cohort 1 during the first summer but mass mortality occurred during the second summer. Mortality in cohort 2 peaked during the first summer. In both cohorts, peak mortality occurred at age 2+ years and thus was uncoupled among cohorts. Therefore, negative environmental factors are ruled out as explanations of mortality. Instead, it appears as if self-thinning interacted with some ontogenetic factor. Although cohort 1 was undergoing self-thinning, trends in biomass–density curves were non-monotonous because of mass mortality. In contrast, self-thinning in cohort 2 followed a classical pattern. One possible mechanism for such contrasting differences was that 1+-year-old scallops produced byssal threads and attached to one another during the first year, forming multilayered clumps. This behaviour disappeared during the second year and mass mortality was experienced as scallops adopted a single-layered arrangement. Although details may differ among species, the process depicted above provides a potential trigger to the sequence of events leading to mass mortality in scallop culture. Our model suggests that self-thinning occurred in all density groups, with a common slope but with different elevations in the biomass–density space.     

Monoclonal gammopathies in the dog: a retrospective study of 18 cases (1986-1999) and literature review

Eighteen dogs with monoclonal gammopathies were evaluated retrospectively. Most of the cases were associated with lymphoproliferative tumors (i.e., nine multiple myelomas, one Waldenstr?m's macroglobulinemia, one lymphoma, one chronic lymphocytic leukemia, and one mucocutaneous plasmacytoma). The prevalence of nonmyelomatous monoclonal gammopathies (28%) was also significant (three leishmaniasis and two ehrlichiosis). Presenting complaints and clinical signs often were nonspecific or related to bleeding diathesis. Significant laboratory findings included proteinuria, hypoalbuminemia, and anemia. Some unusual features were also observed: a multiple myeloma with immunoglobulin M secretion, another myeloma with two narrow spikes on the electrophoretic pattern, and a mucocutaneous plasmacytoma secreting an immunoglobulin G paraprotein.     

Soil sampling based on field spatial variability of soil microbial indicators

Microbial indicators exhibit a high spatial heterogeneity which often masks comparison of the effects of different soil management treatments. It is therefore desirable to use a proper sampling design which integrates spatial heterogeneity at field level. Thus, the objectives were: (1) to study the spatial heterogeneity of biological and chemical soil variables, and (2) with obtained maps of spatial variability to test different sampling strategies to assess the usefulness of this ‘new’ soil map unit. 63 soil samples were collected according to a 10 m × 10 m grid on a 0.48 ha plot. On each of these samples, 10 variables were measured: soil water content, cation exchange capacity (CEC), organic carbon (OC) and total nitrogen (N), C/N, soil microbial biomass (SMB), labile soil organic matter (LOM), mineralisable C (C_min) and N (N_min), inverse of specific respiratory activity (1/SRA = SBM/C_min). The spatial heterogeneity of each variable was charted with geostatistics. The biological variables exhibited spatial variability of the same order of magnitude as physicochemical parameters. From the maps, zones with different levels of organic matter, microbial biomass and specific respiratory activity were identified. The spatial patterns of SMB and SRA were related to CEC (positively for SMB and negatively for SRA), pointing out the effects of soil protection on microbial biomass and availability of organic substrates. The definition of these zones for a pool of variables (OC, N, SMB, LOM, CEC) is useful at 3 levels: (1) to record the initial values of the measured variables for each plot, (2) to integrate these zones as blocks in experimental design for future experiments, and (3) to focus analysis of specific biological mechanisms such as activity of micro-organisms.     

Leaf decomposition in two semi-evergreen tropical forests: influence of litter quality

Decomposition processes in tropical semi-evergreen forests are still poorly understood. The influence of soil properties and litter quality on decomposition rate was studied in two semi-evergreen forests of Guadeloupe, a forest plantation and a secondary forest, located on different soils. Leaf litter of four tree species was enclosed in litterbags for a 14-month period. Non-linear correlations were calculated between mass loss and the concentration of major leaf components (soluble C, N, lignin, cellulose, tannins, total soluble phenols) in order to determine the best predictor of leaf litter decomposition. Soil physico-chemical properties and ratios between some of the above-mentioned litter quality parameters were also examined as mass loss predictors. In addition, non-linear correlations were calculated between mass loss and litter quality parameters, at successive periods. Litter quality was the main determinant of litter decomposition in the studied forests. Several litter quality parameters were correlated with leaf disappearance, varying according to stages of decomposition. Between 1 month and 2.5 months, the mass loss was correlated negatively with the initial phenol content and with initial lignin:N and (lignin+phenol):N ratios. From 2.5 to 5.5 months, the mass loss was correlated negatively with the initial phenol content and positively with the initial cellulose content. At later stages of decomposition (9-14 months), the mass loss was correlated negatively with the initial tannin content. Differences in soil characteristics and fauna did not seem to be enough to affect decomposition.