The study aimed to assess the nutritive value of 10 feeds (grains and forages) commonly used in horse nutrition in Mexico, on the basis of their chemical composition, in vitro organic matter digestibility (IVOMD) and in vitro gas production measurements with or without the supplementation of Saccharomyces cerevisiae (SC) at 4 mg/g DM. Fecal inoculum was obtained from 4 adult English Thoroughbred horses fed on restricted amount of concentrate and oat hay ad libitum. Substrates tested were: 6 concentrates (corn gluten meal, soybean meal, steam-rolled corn, steam-rolled barley, oat grain, and wheat bran) and 4 roughages (soybean hulls, corn stover, alfalfa hay, and oat hay). Gas production (GP) was recorded at 2, 4, 6, 8, 10, 12, 14, 24, 48, and 70 hours using the pressure transducer technique. Some ingredient × yeast interactions were observed (P ≤ .020) for the asymptotic GP and GP at 48 and 70 hours of incubation. Yeast addition increased (P < .001) the asymptotic GP of concentrates compared to roughages. Concentrate feeds had higher (P < .05) GP and lower (P < .001) rate of GP compared to roughages without yeast. From 24 to 70 hours of incubation, forages with or without yeast had lower (P < .05) GP compared to concentrates supplemented with SC. Forages had higher fermentation pH compared to concentrates but lower (P < .05) metabolizable energy, IVOMD, and microbial protein production compared to concentrates. Supplementation with SC increased (P < .05) the asymptotic GP of oat grain, soybean meal, soybean meal, steam-rolled barley, steam-rolled corn, wheat bran, corn stover, and oat hay, without affecting the rate of GP or lag time of oat grain, soybean meal, wheat bran, corn stover, and oat hay. Moreover, supplementation with SC increased (P < .05) metabolizable energy, IVOMD, and microbial protein production of steam-rolled barley, wheat bran, and corn stover, without affecting (P > .05) the fermentation of other feeds. Supplementation with SC improved fermentation of feeds with higher effects on concentrates compared to roughages. It was concluded that although SC mainly improves concentrate utilization by horses, it also improves fiber digestion when used on high-roughage diets fed to horses. 相似文献
Quinclorac is an effective herbicide, but its residue is known to be a major environmental pollutant. Therefore, isolating quinclorac-degrading bacteria, exploring the mechanisms of degradation and analyzing the proteins introduced by the pollutant, would have scientific value and practical importance. We used quinclorac-degrading bacteria WZ1 (an opportunistic pathogen with broad substrate characteristic) as the test strain, and used several techniques such as two-dimensional electrophoresis, gas chromatography-mass spectrometry and Northern Blotting to study the stress response of the strain upon environmental stress and the biodegradation of quinclorac. The results showed that strain WZ1 secreted some protective proteins such as Mn-SOD, Heat-shock protein and Taurine dioxygenase to deal with the stress of quinclorac; while the expression of proteins DsbA and Gmet_1484 related to bacterial pathogenesis decreased significantly when exposed to quinclorac (which could be used to indicate that bacterial pathogenicity was attenuated). At the same time, quinclorac also induced the expression of phthalate dioxygenase reductase and chlorocatechol 1, 2-dioxygenase. They are the key proteins participating in the degradation of quinclorac, which was proved by the Northern Blotting. With the information gathered, we attempted to define the degradation pathway of quinclorac. 相似文献
In the context of climate change, an increased frequency of drought stresses might occur at a regional scale in boreal forests. To assess photosynthetic responses to drought treatment, seedlings of 12 open-pollinated families of white spruce (Picea glauca (Moench) Voss) differing in their growth performance were grown in a controlled environment. Gas exchange and chlorophyll fluorescence parameters as well as shoot xylem water potential (WP) were measured for 21 successive days after watering was stopped. Net photosynthesis decreased as stomatal conductance decreased. Net photosynthesis was not affected by drought until WP reached –2.0 MPa when stomata were closed. Initial fluorescence (F and basic fluorescence after induction (F00) were not affected by drought. A progressive decrease in maximal (Fm) and variable fluorescences (Fv), maximum photosystem II (PS II) efficiency (Fv = Fm), effective quantum yield of PS II (FII), photochemical efficiency of open PS II (Fp), and photochemical quenching (qP) was observed at WP < - 1.0 MPa, whereas non-photochemical quenching (qN) remained high throughout the drought treatment. White spruce families with inferior growth performance showed higher values of Fm, Fv, Fv = Fm, Fp, and qN at WP< - 2.0MPa. The results indicated that chlorophyll fluorescence variables can be used as drought markers in relation to present or predicted climate conditions. These could be used for selecting planting stock adapted to drought periods or dry environments. These markers showed that slow-growing genotypes are better adapted to drought conditions than intermediate or fast-growing genotypes in present and predicted drought conditions. 相似文献
About 240 x 106 tonnes of industrial waste, 104 x 106 tonnes of municipal waste and more than 60 x 106 tonnes of sediment sludge are landfilled (65 per cent), incinerated (24 per cent) and partly recycled in Europe annually. About 60000-120000 landfill sites, occupying 800-1700 km2, are recorded in the EEC, of which a limited number are in operation. These sites generate 12.5 x 109 m3 of landfill gas annually, of which about 755 x 106 m3 are presently recovered, and 0-1-4-0 x 106 m3 of heavily polluted leachate, which is dispersed to ground and surface waters. the area with polluted groundwater increases annually by 1-10 per cent (1200-12000 km2 of contaminated land). Landfill gas contains carcinogenic and pathogenic components and contributes 2 per cent of the total emission of greenhouse gases; locally it is a potential hazard. Incinerators reduce the solid volume to about 30 per cent of the original but cause the atmospheric deposition of acids and dioxins. Emissions of landfill gas, leachate and atmospheric deposition have been recognized as potential chemical time bombs (CTBs). Models are currently available for the estimation of the time at which the effects of these CTBs will become manifest. It is recommended that an inventory of all landfills should be made to assess the potential hazards in detail, to encourage institutions to initiate the clean-up of contaminated sites and the aftercare of closed sites, and to set up a co-operative network within the EEC. 相似文献
Management of crop residues and soil organic matter is of primary importance in maintaining soil fertility and productivity and in minimizing agricultural impact on the environment. Our objective was to determine the effects of traffic and tillage on short-term carbon dioxide (CO2) and water (H2O) fluxes from a representative soil in the southeastern Coastal Plain (USA). The study was conducted on a Norfolk loamy sand (FAO classification, Luxic Ferralsols; USDA classification, fine-loamy siliceous, thermic Typic Kandiudults) cropped to a corn (Zea mays L.) — soybean (Glycine max (L.) Merr) rotation with a crimson clover (Trifolium incarnatum L.) winter cover crop for eight years. Experimental variables were with and without traffic under conventional tillage (CT) (disk harrow twice, chisel plow, field cultivator) and no tillage (NT) arranged in a split-plot design with four replicates. A wide-frame tractive vehicle enabled tillage without wheel traffic. Short-term CO2 and H2O fluxes were measured with a large portable chamber. Gas exchange measurements were made on both CT and NT at various times associated with tillage and irrigation events. Tillage-induced CO2 and H2O fluxes were larger than corresponding fluxes from untilled soil. Irrigation caused the CO2 fluxes to increase rapidly from both tillage systems, suggesting that soil gas fluxes were initially limited by lack of water. Tillage-induced CO2 and H2O fluxes were consistently higher than under NT. Cumulative CO2 flux from CT at the end of 80 h was nearly three times larger than from NT while the corresponding H2O loss was 1.6 times larger. Traffic had no significant effects on the magnitude of CO2 fluxes, possibly reflecting this soil’s natural tendency to reconsolidate. The immediate impact of intensive surface tillage of sandy soils on gaseous carbon loss was larger than traffic effects and suggests a need to develop new management practices for enhanced soil carbon and water management for these sensitive soils. 相似文献
Two field experiments were carried out to investigate the effects of terminal drought on chickpea grown under water-limited conditions in the Mediterranean-climatic region of Western Australia. In the first experiment, five desi (small angular seeds) chickpeas and one kabuli (large round seeds) chickpea were grown in the field with and without irrigation after flowering. In the second experiment, two desi and two kabuli cultivars were grown in the field with either irrigation or under a rainout shelter during pod filling. Leaf water potential (Ψl), dry matter partitioning after pod set and yield components were measured in both experiments while growth before pod set, photosynthesis, pod water potential and leaf osmotic adjustment were measured in the first experiment only.
In the first experiment, total dry matter accumulation, water use, both in the pre- and post-podding phases, Ψl and photosynthesis did not vary among genotypes. In the rainfed plants, Ψl decreased below −3 MPa while photosynthesis decreased to about a tenth of its maximum at the start of seed filling. Osmotic adjustment varied significantly among genotypes. Although flowering commenced from about 100 days after sowing (DAS) in both experiments, pod set was delayed until 130–135 DAS in the first experiment, but started at 107 DAS in the second experiment. Water shortage reduced seed yield by 50 to 80%, due to a reduction in seed number and seed size. Apparent redistribution of stem and leaf dry matter during pod filling varied from 0 to 60% among genotypes, and suggests that this characteristic may be important for a high harvest index and seed yield in chickpea. 相似文献