Disposable cartridge extraction of retinol and alpha-tocopherol from feedstuffs

Automated determination of fat-soluble vitamins by modern methods such as liquid chromatography is hampered by the initial extraction step. A simple technique is proposed that allows an appreciable increase in the actual rates of determination. Feedstuff samples are first hydrolyzed in an aqueous alcohol (mainly methanol)-potassium hydroxide solution. Instead of extracting retinol and alpha-tocopherol from the hydrolysis solution by an organic solvent, an aliquot of the solution is mixed with a small volume of a strong antioxidant solution (ascorbic acid) and pipetted onto a kieselguhr disposable cartridge where it is adsorbed. Retinol and alpha-tocopherol are eluted with isooctane at normal pressure. The proposed method has been compared with conventional techniques on many feed samples.     

Concurrent overproduction of synapses in diverse regions of the primate cerebral cortex

Synapses develop concurrently and at identical rates in different layers of the visual, somatosensory, motor, and prefrontal areas of the primate cerebral cortex. This isochronic course of synaptogenesis in anatomically and functionally diverse regions indicates that the entire cerebral cortex develops as a whole and that the establishment of cell-to-cell communication in this structure may be orchestrated by a single genetic or humoral signal. This is in contrast to the traditional view of hierarchical development of the cortical regions and provides new insight into the maturation of cortical functions.     

La Stéatose Hépatique et la Cholestérolémie Chez le Caneton Domestique au Cours d'une Malnutrition Protéique en Régime Orizé

The object of this experiment was to study the influence of essential amino acids on the growth, fatty infiltration of liver and cholesterol level of the serum in ducklings.     

Seroprevalence of Rift Valley fever virus in cattle in the Democratic Republic of the Congo

Tropical Animal Health and Production - This study aimed at assessing the serological and virological status of Rift Valley fever virus (RVFV) in cattle from four climatically diverse zones of the...     

Ecological niche partitioning between Anopheles gambiae molecular forms in Cameroon: the ecological side of speciation

Background  

Speciation among members of the Anopheles gambiae complex is thought to be promoted by disruptive selection and ecological divergence acting on sets of adaptation genes protected from recombination by polymorphic paracentric chromosomal inversions. However, shared chromosomal polymorphisms between the M and S molecular forms of An. gambiae and insufficient information about their relationship with ecological divergence challenge this view. We used Geographic Information Systems, Ecological Niche Factor Analysis, and Bayesian multilocus genetic clustering to explore the nature and extent of ecological and chromosomal differentiation of M and S across all the biogeographic domains of Cameroon in Central Africa, in order to understand the role of chromosomal arrangements in ecological specialisation within and among molecular forms.     

Living at the edge: biogeographic patterns of habitat segregation conform to speciation by niche expansion in Anopheles gambiae

Background

Ongoing lineage splitting within the African malaria mosquito Anopheles gambiae is compatible with ecological speciation, the evolution of reproductive isolation by divergent natural selection acting on two populations exploiting alternative resources. Divergence between two molecular forms (M and S) identified by fixed differences in rDNA, and characterized by marked, although incomplete, reproductive isolation is occurring in West and Central Africa. To elucidate the role that ecology and geography play in speciation, we carried out a countrywide analysis of An. gambiae M and S habitat requirements, and that of their chromosomal variants, across Burkina Faso.

Results

Maps of relative abundance by geostatistical interpolators produced a distinct pattern of distribution: the M-form dominated in the northernmost arid zones, the S-form in the more humid southern regions. Maps of habitat suitability, quantified by Ecological Niche Factor Analysis based on 15 eco-geographical variables revealed less contrast among forms. M was peculiar as it occurred proportionally more in habitat of marginal quality. Measures of ecological niche breadth and overlap confirmed the mismatch between the fundamental and realized patterns of habitat occupation: forms segregated more than expected from the extent of divergence of their environmental envelope – a signature of niche expansion. Classification of chromosomal arm 2R karyotypes by multilocus genetic clustering identified two clusters loosely corresponding to molecular forms, with 'mismatches' representing admixed individuals due to shared ancestral polymorphism and/or residual hybridization. In multivariate ordination space, these karyotypes plotted in habitat of more marginal quality compared to non-admixed, 'typical', karyotypes. The distribution of 'typical' karyotypes along the main eco-climatic gradient followed a consistent pattern within and between forms, indicating an adaptive role of inversions at this geographical scale.

Conclusion

Ecological segregation between M and S is consistent with niche expansion into marginal habitats by chromosomal inversion variants during early lineage divergence; presumably, this process is promoted by inter-karyotype competition in the higher-quality core habitat. We propose that the appearance of favourable allelic combinations in other regions of suppressed recombination (e.g. pericentromeric portions defining speciation islands in An. gambiae) fosters development of reproductive isolation to protect linkage between separate chromosomal regions.     

Increased productivity through integrated soil fertility management in cassava–legume intercropping systems in the highlands of Sud-Kivu,DR Congo

Smallholder farmers in sub-Saharan Africa are confronted by low productivity and limited investment capacity in nutrient inputs. Integrated soil fertility management (ISFM) aims at increased productivity through the combined use of improved germplasm, judicious fertilizer application and organic matter management, adapted to the local farming conditions. We hypothesize that the application of these different ISFM components can result in significant increases in productivity and economic benefits of cassava–legume intercropping systems. Participatory demonstration trials were conducted in the highlands of Sud-Kivu, DR Congo with 12 farmer groups during 3 seasons. Treatments included the farmers’ common practice (local common bean and cassava varieties, seed broadcast and manure addition) and sequentially added ISFM components: improved bean and cassava germplasm, modified crop arrangements, compound NPK fertilizer application and alternative legume species (groundnut or soybean). The use of improved germplasm did not result in yield increases without simultaneous implementation of other ISFM components. Modifying the crop arrangement by planting cassava at 2 m between rows and 0.5 m within the row, intercropped with four legume lines, increased bean yields during the first season and permits a second bean intercrop, which can increase total legume production by up to 1 t ha⁻¹ and result in an additional revenue of almost 1000 USD ha⁻¹. Crop arrangement or a second legume intercrop did not affect cassava storage root yields. Fertilizer application increased both legume and cassava yield, and net revenue by 400–700 USD ha⁻¹ with a marginal rate of return of 1.6–2.7. Replacing the common bean intercrop by groundnut increased net revenue by 200–400 USD ha⁻¹ partly because of the higher market value of the grains, but mostly due to a positive effect on cassava storage root yield. Soybean affected cassava yields negatively because of its high biomass production and long maturity period; modifications are needed to integrate a soybean intercrop into the system. The findings demonstrate the large potential of ISFM to increase productivity in cassava–legume systems in the Central-African highlands. Benefits were, however, not observed in all study sites. In poor soils, productivity increases were variable or absent, and soil amendments are required. A better understanding of the conditions under which positive effects occur can enable better targeting and local adaptation of the technologies.     

Efficiency of working dogs undergoing a new Human Familiarization and Training Program

The study of human-dog interaction has increased over the past several years. It has been demonstrated that dogs can use a number of human social cues to successfully accomplish a task, and that they do so better than apes. Many authors agree that these abilities are a result of 10,000 years of domestication by humans. Domestication may have genetically predisposed dogs to accurately recognize human communication signals. However, only a few authors have studied the performance of working dogs, implying recognition of human communication signals. Haverbeke et al. (2008) found that military working dogs do not always perform as they are expected to. To investigate this finding, we studied the performance of obedience and protection work exercises between 2 groups of dog-handler teams: a control group (CG), trained using the current training method used by the Belgian Defense, and an experimental group (EG) that underwent a new human familiarization and training program. During obedience and protection work exercises, EG teams obtained better results than CG teams and EG dogs exhibited a higher body posture than CG dogs. The results suggest that even if dogs are genetically predisposed toward the recognition of human communication signals, this aptitude alone does not explain the dogs' performance and their interactions with humans in this study. Regular training combined with positive dog-handler interaction is also required to increase the dog-handler (DH) team's performances.     

GAMEDE: A global activity model for evaluating the sustainability of dairy enterprises Part I – Whole-farm dynamic model

 Crop-livestock farms are complex systems. The interactions operating in such systems involve decisional, biophysical, structural, and environmental factors. Moreover, as farmers face a large range of management options, tools are needed to support their decision-making to enable them to reach production levels meeting their objectives and compatible with their human and physical resources, while controlling their effects on the environment. Gamede, a whole-dairy-farm model, has been developed to explore this complexity and to represent dynamically the effect of management decisions on biomass and nitrogen flows and on numerous sustainability indicators, such as milk and forage crop productivity, labour requirements, nitrogen balance, and nitrogen efficiency.This article describes the integration of six modules accounting for biophysical processes in a dairy farm (forage production; forage conditioning; herd demography; milk, excreta and animal biomass productions; grazing, quality of fertilisers; and nitrogen gaseous emissions) together with a decision system accounting for the farmer’s strategy and technical operations. Most of the six biophysical modules incorporate mathematical models from the literature, but the decision system stems from our own original work.Six commercial farms with different structures, agro-climatic conditions and management strategies were used for validation. The model can explain the differences found in their sustainability indicators at the year scale. The intra-year variability of the main biomass stocks and flows is also well explained. This quantitative validation was completed by a qualitative validation from researcher, adviser and farmer points of view, including simulations of prospective scenarios.     

Xylella fastidiosa subspecies and sequence types detected in Philaenus spumarius and in infected plants in France share the same locations

In Europe, the meadow spittlebug Philaenus spumarius is the main known vector of the quarantine bacterium Xylella fastidiosa. So far detection and identification of X. fastidiosa has more often been performed from plant matrices than insects, mainly using a real-time PCR and multilocus sequence typing (MLST) approach. Detection of X. fastidiosa in its insect vectors would enhance knowledge of the epidemiologic situation in France, specifically in the already infected Corsica and Provence-Alpes-Côte d’Azur (PACA) regions. The aim of this study was to validate a methodological approach to detect X. fastidiosa in P. spumarius, analysed individually or in groups of 10, using real-time PCR and MLST, and to apply the approach to more than 4,000 individuals collected between 2015 and 2019 from infected areas. The corresponding results expanded our knowledge of the epidemiology of X. fastidiosa in France: (a) X. fastidiosa subsp. multiplex including the sequence types ST6 and ST7 were identified in the insect vector; (b) the rate of positive insects per infected area was as high as 33.3% in Corsica or 50% in the PACA region; (c) positive adults were found during winter; and (d) the bacterial load in P. spumarius (droplet digital PCR) usually ranged from 10³ to 10⁴ cells per insect, but could be as high as 10⁵ or 10⁶ cells per insect for some individuals (13%). The subspecies and sequence types detected in P. spumarius corresponded to the situation officially reported for plants in the same areas.