Effect of feeding fermentable fiber on synthesis of total and mucosal protein in the intestine of the growing pig

In a previous study, a reduced efficiency of ileal digestible threonine (THR) use for body protein deposition was observed in growing pigs when pectin was included in the diet. This response was not due to increased physical endogenous ileal THR loss. Our aim was to explore the contribution of diet-induced increases in protein synthesis in the colon, especially mucins, to dietary THR requirements. Twelve barrows (21 kg mean BW) were fed either a cornstarch–soybean meal-based diet (Control) or Control with 12% pectin (Pectin). Pigs were given intravenously 1.5 mmol/kg BW of L-1-¹³C valine (40 mol%) to measure fractional and absolute synthesis rates (FSR, ASR, respectively) of mucosal and whole intestinal protein in the jejunum and colon. Dietary pectin inclusion increased plasma levels of glucose, isoleucine and glutamine (P < 0.05) but had no effect on insulin or urea nitrogen (P > 0.10). There were no differences in FSR and ASR of whole intestinal protein in jejunum and colon (P > 0.10). The FSR of mucosal proteins in colon, not in jejunum, was increased with dietary pectin supplementation (P < 0.05). Assuming mucosal protein mass is constant, these results imply that the higher protein synthesis in colon mucosa contributes to the reduced THR efficiency observed in pectin-supplemented diet.     

Major gene resistance in Brassica napus (oilseed rape) is overcome by changes in virulence of populations of Leptosphaeria maculans in France and Australia

Resistance of Brassica napus (oilseed rape, canola) conferred by three different major resistance genes has been overcome by changes in virulence of Leptosphaeria maculans populations in France and Australia. In South Australia where B. napus cultivars with major gene resistance derived from Brassica rapa ssp. sylvestris were grown extensively, resistance was rendered ineffective within 3 years of commercial release of the cultivar. Disease severity was higher on cultivars with sylvestris-derived resistance than cultivars with polygenic resistance. This Australian situation is compared to that in France, where resistance conferred by the Rlm1 gene was overcome nation-wide in 5 years under commercial cropping practices, and also where a source of resistance introgressed into B. napus from B. juncea was rendered inefficient in 3 years in experimental field plots near Rennes.     

Accumulation of acaricide resistance mechanisms in Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) populations from New Caledonia Island

Rhipicephalus (Boophilus) microplus has been pesticide-controlled for several decades in the pacific island of New Caledonia. Since 1996, pesticide-control has been based on either deltamethrin (Butox) or amitraz (Taktic) in herds harbouring deltamethrin-resistant ticks. In this island, the first R. microplus deltamethrin- and amitraz-resistances were detected in 1992 and 2003, respectively. Using LPT bioassays, we have undertaken to update data regarding the geographical distribution and the physiological diversity likely to be involved in these resistances. We confirmed that after 17 years of intensive use of deltamethrin, several resistances of moderate levels (<30-fold) have evolved and/or diffused in any part of the island. We also evidenced that amitraz-resistant phenotypes have recently evolved in diverse western tick populations, although none has reached fixation in any tick population yet. According to synergists bioassays, the physiological changes involved in amitraz-resistance in New Caledonia would involve target modification and detoxifying P450 cytochrom oxydase(s). It may also involve detoxifying esterase(s) although this later point will need confirmation on samples bearing higher frequency of resistant phenotypes. Results are discussed with regard to the local evolutionary dynamics of resistance.     

Economies of scale for juvenile production of common snook (Centropomus undecimalis Bloch)

Abstract

Construction and operating costs for three common snook (Centropomus undecimalis) hatcheries in Florida, USA, are illustrated. Hypothetical capacities and targets of the three hatcheries (Scenarios I, II and III respectively) were 615, 000 juveniles (8 ‐ 10 g in weight) for stock enhancement, and 1, 275, 000 and 3, 000, 000 juveniles (1‐g in weight) for commercial grow‐out. Estimated production costs were lower than for many marine finfish species. The 20‐year mean costs per 1, 000 juveniles were estimated to be $324, $215, and $159, for hatcheries I, II, and III respectively, and the initial capital investments were $731, 660, $1, 162, 460, and $1, 896, 030¹, respectively. Major cost items of annual production were labor (22 ‐ 33%), supplies (14 ‐ 20%), fixed costs (15 ‐ 17%), and interest (13 ‐ 15%). The most profitable hatchery was the 3 million 1‐g juvenile hatchery due to the hatchery size effect, with a net present value (NPV) of $1, 760, 000, an internal rate of return (ERR) of 81%, a payback period of 3.6 years, and a profitability index of $2.86 for every dollar invested. Possible cost reductions to increase financial profitability were discussed.     

Developmental progression of immunoglobulin heavy chain diversity in sheep

In order to assess the respective impacts of combinatorial rearrangement, junctional diversification, somatic hypermutation and gene conversion in the generation of immunoglobulin heavy chain variable regions diversity, the sequences of 42 variable regions from late fetal, newborn and young sheep were determined and compared to those of adult animals. At earlier stages of development, the use of germline diversity segments appears restricted, junctional variability is already established, and somatic hypermutations are scarce. The sequence diversity in adults is much higher, which we suggest results from a higher hymermutation activity and possibly from the use of a variety of diversity segments. Altogether, this pattern is very reminiscent of the situation observed in cattle, except for the length of the third complementarity determining regions (CDR3) which are shorter in sheep than in bovine. Unlike the chicken and rabbit systems, it seems that new rearrangements continue to occur in sheep for at least several months after birth.     

A class of potent antimalarials and their specific accumulation in infected erythrocytes

During asexual development within erythrocytes, malaria parasites synthesize considerable amounts of membrane. This activity provides an attractive target for chemotherapy because it is absent from mature erythrocytes. We found that compounds that inhibit phosphatidylcholine biosynthesis de novo from choline were potent antimalarial drugs. The lead compound, G25, potently inhibited in vitro growth of the human malaria parasites Plasmodium falciparum and P. vivax and was 1000-fold less toxic to mammalian cell lines. A radioactive derivative specifically accumulated in infected erythrocytes to levels several hundredfold higher than in the surrounding medium, and very low dose G25 therapy completely cured monkeys infected with P. falciparum and P. cynomolgi.     

Mechanisms of resistance to fungicides in field strains of Botrytis cinerea

Field strains of Botrytis cinerea Pers ex Fr, the causal agent of grey mould diseases, were collected from French vineyards between 1993 and 2000. Several phenotypes have been characterized according to the inhibitory effects of fungicides towards germ-tube elongation and mycelial growth. Two types of benzimidazole-resistant strains (Ben R1 and Ben R2) could be detected; negative cross-resistance to phenylcarbamates (e.g. diethofencarb) was only found in Ben R1. Benzimidazole resistance was related to point mutations at codon 198 (Ben R1) or 200 (Ben R2) of the beta-tubulin gene. Most dicarboximide-resistant strains were also weakly resistant to aromatic hydrocarbon fungicides (e.g. dicloran) but remained sensitive to phenylpyrroles (e.g. fludioxonil). These resistant field strains (Imi R1) contained a single base pair mutation at position 365 in a two-component histidine kinase gene, probably involved in the fungal osmoregulation. Three anilinopyrimidine-resistant phenotypes have been identified. In the most resistant one (Ani R1), resistance was restricted to anilinopyrimidines, but no differences were observed in the amino-acid sequences of cystathionine beta-lyase (the potential target site of these fungicides) from Ani R1 or wild-type strains. In the two other phenotypes (Ani R2 and Ani R3), resistance extended to various other groups of fungicide, including dicarboximides, phenylpyrroles and sterol biosynthesis inhibitors. This multi-drug resistance was probably determined by over-production of ATP-binding cassette transporters. The hydroxyanilide fenhexamid is a novel botryticide whose primary target site is the 3-keto reductase involved in sterol C-4 demethylations. Apart from the multi-drug-resistant strain Ani R3, three other fenhexamid-resistant phenotypes have been recognized. For two of them (Hyd R1 and Hyd R2) fenhexamid-resistance seemed to result from P450-mediated detoxification. Reduced sensitivity of the target site could be the putative resistance mechanism operating in the third resistant phenotype (Hyd R3). Increased sensitivity to inhibitors of sterol 14 alpha-demethylase recorded in Hyd R1 strains was related to two amino-acid changes at positions 15 and 105 of this enzyme.     

The role of models for multicriteria evaluation and multiobjective design of cropping systems for managing weeds

Weeds are both harmful for crop production and important for biodiversity, while herbicides can pollute the environment. We thus need new cropping systems optimising all cultural techniques, reconciling agricultural production, herbicide reduction and biodiversity conservation. Here, we show how to (i) develop models quantifying the effects of cropping systems on weed dynamics, (ii) integrate interactions between weeds and other organisms, (iii) predict the impact on production and biodiversity and (iv) use the model for multicriteria evaluation and multiobjective design of cropping systems. Among the existing weed dynamics models, we chose the one closest to our requirements to illustrate these different steps, that is, FlorSys which predicts multispecific weed dynamics as a function of cultural techniques and pedoclimate. We have illustrated the development of interaction submodels with the example of a crop pathogen whose propagation is increased when infecting grass weeds. To evaluate the weed flora impact, predicted weed densities were translated into indicators of harmfulness (crop yield loss, technical harvest problems, harvest pollution, field infestation, crop disease increase) and biodiversity (weed species richness and equitability, trophic resources for birds, insects and pollinators). Simulations were run over several years and with different weather scenarios (i) to optimise cultural techniques to control harmful weeds, (ii) to analyse the impact of changing agricultural practices (e.g. simplified tillage and rotations, no‐till, temporary crops) on weed density, species and trait composition and (iii) to evaluate cropping systems for their ability to reconcile agricultural production and biodiversity, thus identifying levers for designing sustainable cropping systems.