Zootechnical and physiological responses of whiteleg shrimp (Litopenaeus vannamei) postlarvae reared in bioflocs and subjected to stress conditions during nursery phase     

Enrique Guemez‐Sorhouet  Humberto Villarreal  Ilie S. Racotta  Jos Naranjo  Laurence Mercier 《Aquaculture Research》2019,50(4):1198-1211

The objective of this study was to assess zootechnical and physiological performance of Litopenaeus vannamei postlarvae (PL) reared in three environments (CW, clear water; B, biofloc; BS, biofloc with artificial substrates) at three stocking densities (300, 600, 900 PL/m³) for 8 weeks. At the end of experimentation, shrimp were subjected to hypoxia, and physiological response was again assessed. During rearing, low levels of total ammonia nitrogen, nitrite (NO₂^?) and nitrate (NO₃^?) were observed in B and BS for 600 and 900 PL/m³. For 300 PL/m³, a slight accumulation of NO₂^? and NO₃^? was detected. For the same stocking density, shrimp reared in B and BS showed significantly higher weights than those grown in CW, except for final weight. No significant differences were observed in survival. The use of biofloc and artificial substrates permitted doubling density from 300 to 600 PL/m³ without affecting growth, survival, feed conversion rate and obtaining twice the biomass. Shrimp grown in B and BS stored a surplus of glycogen and carbohydrates in their hepatopancreas, which probably gave them a better physiological capacity to counteract high‐stocking densities and hypoxia. A tendency of a higher adenylate energetic charge was observed in shrimp maintained in B and BS.  相似文献   

"Two heads are better" stands to reason     

Mercier H  Sperber D 《Science (New York, N.Y.)》2012,336(6084):979

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Toxoplasma gondii infection in sheep from Haute-Vienne, France: seroprevalence and isolate genotyping by microsatellite analysis     

Dumètre A  Ajzenberg D  Rozette L  Mercier A  Dardé ML 《Veterinary parasitology》2006,142(3-4):376-379

Ingesting meat of free-range livestock, mainly sheep, is associated with human toxoplasmosis in European countries. Data on Toxoplasma gondii infection in French ovine livestock are relatively scarce. Sera from 164 lambs and 93 ewes slaughtered in Haute-Vienne district, France, were tested by a direct agglutination test. Antibodies to T. gondii were found in 36 (22.0%) lambs and in 61 (65.6%) ewes. In addition, to attempt parasite isolation for genotyping, hearts from 50 other ewes were obtained from a local slaughterhouse, and were screened by a direct agglutination test. T. gondii was isolated in 8 of 30 seropositive hearts bioassayed in mice. All isolates were type II by genetic characterization at five microsatellite loci (TUB2, TgM-A, W35, B17, B18). These results indicate that bovines slaughtered in France may be highly infected by T. gondii with a potential risk of parasite transmission to humans by consumption of undercooked meat. Multilocus microsatellite analysis shows the predominance of type II in sheep as previously described in humans.  相似文献   

Gene expression differences in the methionine remethylation and transsulphuration pathways under methionine restriction and recovery with D,L‐methionine or D,L‐HMTBA in meat‐type chickens          下载免费PDF全文

S. E. Aggrey  F. González‐Cerón  R. Rekaya  Y. Mercier 《Journal of animal physiology and animal nutrition》2018,102(1):e468-e475

This study examined the molecular mechanisms of methionine pathways in meat‐type chickens where birds were provided with a diet deficient in methionine from 3 to 5 weeks of age. The birds on the deficient diet were then provided with a diet supplemented with either D,L‐methionine or D,L‐HMTBA from 5 to 7 weeks. The diet of the control birds was supplemented with L‐methionine from hatch till 7 weeks of age. We studied the mRNA expression of methionine adenosyltransferase 1, alpha, methionine adenosyltransferase 1, beta, 5‐methyltetrahydrofolate‐homocysteine methyltransferase, 5‐methyltetrahydrofolate‐homocysteine methyltransferase reductase, betaine‐homocysteine S‐methyltransferase, glycine N‐methyltransferase, S‐adenosyl‐L‐homocysteine hydrolase and cystathionine beta synthase genes in the liver, duodenum, Pectoralis (P.) major and the gastrocnemius muscle at 5 and 7 weeks. Feeding a diet deficient in dietary methionine affected body composition. Birds that were fed a methionine‐deficient diet expressed genes that indicated that remethylation occurred via the one‐carbon pathway in the liver and duodenum; however, in the P. major and the gastrocnemius muscles, gene expression levels suggested that homocysteine received methyl from both folate and betaine for remethylation. Birds who were switched from a methionine deficiency diet to one supplemented with either D,L‐methionine or D,L‐HMTBA showed a downregulation of all the genes studied in the liver. However, depending on the tissue or methionine form, either folate or betaine was elicited for remethylation. Thus, mRNA expressions show that genes in the remethylation and transsulphuration pathways were regulated according to tissue need, and there were some differences in the methionine form.  相似文献   

Optimization of arsenic and pentachlorophenol removal from soil using an experimental design methodology     

Nicolas Reynier  Jean-François Blais  Guy Mercier  Simon Besner 《Journal of Soils and Sediments》2013,13(7):1189-1200

Purpose

In this study, a soil-washing process was investigated for arsenic (As) and pentachlorophenol (PCP) removal from polluted soils. This research first evaluates the use of chemical reagents (HCl, HNO₃, H₂SO₄, lactic acid, NaOH, KOH, Ca(OH)₂, and ethanol) for the leaching of As and PCP from polluted soils.

Materials and methods

A Box–Behnken experimental design was used to optimize the main operating parameters for soil washing. A laboratory-scale leaching process was applied to treat four soils polluted with both organic ([PCP] _i ?=?2.5–30 mg kg^?1) and inorganic ([As] _i ?=?50–250 mg kg^?1, [Cr] _i ?=?35–220 mg kg^?1, and [Cu] _i ?=?80–350 mg kg^?1) compounds.

Results and discussion

Removals of 72–89, 43–62, 52–68, and 64–98 % were obtained for As, Cr, Cu, and PCP, respectively, using the optimized operating conditions ([NaOH]?=?1 N, [cocamidopropylbetaine] _i ?=?2 % w w^?1, t?=?2 h, T?=?80 °C, and PD?=?10 %).

Conclusions

The use of NaOH, in combination with the surfactant, is efficient in reducing both organic and inorganic pollutants from soils with different levels of contamination.  相似文献   

Biofilm formation vs. PCB adsorption on granular activated carbon in PCB-contaminated aquatic sediment     

Anne Mercier  Guillaume Wille  Caroline Michel  Jennifer Harris-Hellal  Laurence Amalric  Catherine Morlay  Fabienne Battaglia-Brunet 《Journal of Soils and Sediments》2013,13(4):793-800

Purpose

Granular activated carbon (GAC) that is both an efficient polychlorinated biphenyl (PCB) adsorbent and a good growth support for microorganisms is considered suitable for in situ remediation of PCB-contaminated aquatic sediment. Here, the potential competition between biofilm formation and PCB (Aroclor 1260) adsorption on GAC in a PCB-contaminated aquatic sediment was investigated.

Materials and methods

GACs, both coated and uncoated with biofilm or PCBs, were incubated with sediment. Each was monitored for biofilm development and PCB adsorption by: (a) cryo-scanning electron microscopy, (b) real-time quantitative PCR analysis of the 16S rRNA, (c) terminal restriction fragment length polymorphism and (d) chemical analysis.

Results and discussion

Biofilm formation on the GAC by the sediment's bacteria was rapid and occurred in three stages: (1) initial adherence of discrete bacteria, (2) an increase in biomass associated with a shift in bacterial diversity and (3) exopolymeric matrix production. The density and biodiversity of the multispecies biofilm depended on the biofilm's age. The addition of Aroclor 1260 to the sediment resulted in a decrease of the biofilm biomass, whereas Aroclor 1260 previously adsorbed on the GAC prior to contact with the sediment did not influence the biofilm biomass or its formation dynamics. Similarly, a biofilm previously developed on the GAC did not significantly decrease PCB adsorption, although contact of the GAC with the sediment did hamper adsorption of the higher chlorinated PCB congeners.

Conclusions

A mature multispecies bacterial biofilm developed in 1 month on GAC in contact with aquatic sediment did not hamper PCB adsorption, and PCB adsorption did not influence biofilm formation. These findings are important for the application of remediation strategies.  相似文献   

In situ forcing of pollen maturation in Jack pine and Japanese larch male cones     

Stéphan Mercier 《New Forests》1995,9(3):261-272

Paper bags equipped with a polyethylene window were placed on branchlets 6 and 9 weeks before the time of pollen dispersal of Japanese larch and Jack pine, respectively. This technique produced a localized greenhouse effect around the branchlets, accelerating male cone development. For Jack pine trees, buds in bags with the window oriented upward had the shortest maturation time. In fact, it was possible to collect these pollen cones about 11 days before the unbagged control without decreasing the production of pollen. The mean germination rate of the pollen from the bags with the window pointed upward, however, was significantly lower than the control, by about 15%. Buds in bags with the window oriented downward had an accelerated development of about 9 days (compared to the control) but did not experience a decrease in pollen production or quality. This same technique caused the abortion of male cones of the Japanese larch trees. Thermal probes in the bags enabled us to follow the progression of temperature inside and outside the bags during the development of the male cone in each species. They revealed that the bags increased mean temperature, daily temperature range, and degree-day accumulation, and that this effect was most pronounced for Jack pine, when the polyethylene window was oriented upward.  相似文献   

Characterisation of Mycoplasma capricolum P60 surface lipoprotein and its evaluation in a recombinant ELISA     

Alberti A  Robino P  Chessa B  Rosati S  Addis MF  Mercier P  Mannelli A  Cubeddu T  Profiti M  Bandino E  Thiery R  Pittau M 《Veterinary microbiology》2008,128(1-2):81-89

This paper reports the identification and characterisation of a 60kDa surface protein antigen (P60) of Mycoplasma capricolum subspecies capricolum (Mcc), and describes its diagnostic application. Genomic localization and presence in P60 of conserved functional domains suggested a structural and functional relationship with the immunodominant antigen P48 of Mycoplasma agalactiae, a basic membrane protein. A rP60-ELISA was developed, and it resulted in a high specificity for Mcc infections after evaluation with 125 goat sera. The comparison with an existent ELISA based on whole Mcc cell lysates showed that the two assays have comparable sensitivities, but the rP60-ELISA has the significant advantage of a greater specificity. Results indicate that P60 is a potential marker of Mcc infection, especially useful in areas where the presence of M. capricolum subspecies capripenumoniae is also reported.  相似文献   

Perception of needs and responses in food security: divergence between households and stakeholders     

Hamelin AM  Mercier C  Bédard A 《Public health nutrition》2008,11(12):1389-1396

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Preventing transmission of sarcoptic mange from sows to their offspring by injection of ivermectin. Effects on swine production     

Mercier P  Cargill CF  White CR 《Veterinary parasitology》2002,110(1-2):25-33

A blind and controlled field study was conducted on a pig farm in Australia to evaluate the activity of 1% ivermectin solution when injected into pregnant sows that were naturally infested with mites. The study was designed to appreciate the tolerance of the product on sows (litter size, litter birth weights, litter weaning weights, pre-weaning mortality) and to show the effects of sarcoptic mange on the growth performances of their offspring. Twenty sows were selected and ranked on Day-10, prior to the start of the study, on the basis of positive mite counts and parity. Sows were randomly allocated into two groups, A and B. On Day-7, they were injected once with product A (1 ml/33 kg; yielding 300 microg ivermectin/kg BW) or product B (placebo), respectively and then moved to the farrowing unit. Mite counts, ear and body lesions were scored and recorded. The average daily weight gain (ADG) was calculated on piglets from birth to Day-45 (ADG(45)) and birth to Day-70 (ADG(70)). Ivermectin was 100% efficient in preventing the transmission of scabies mites and did not have negative effect on the pregnant sows. Growth performances (ADG(45) and ADG(70)) of piglets from treated sows were significantly higher (452 and 541.5 g per day) than that from untreated sows (433.5 and 518.4 g per day) respectively, confirming that sarcoptic mange is detrimental to the production performances of growing pigs.  相似文献