Significant portions of grain produced for livestock consumption are convened into ensiled forage. Silage producers have long recognized the positive effects of using an inoculant to insure the proper transformation of forage into a palatable and digestible feedstuff. When silage is fed from a storage structure, exposure to air stimulates the growth of epiphytic aerobes that may result in the loss of up to 50% of the dry matter. Moreover, fungi have been found to be associated with ensiled forage, but their growth is normally suppressed by the anaerobic conditions. However, the introduction of oxygen results in a fungal bloom, and the fungi and the associated metabolites may result in lost productivity in the livestock consuming the contaminated forage. In this study, we report on the diversity of the fungal community associated with whole plant corn silage during the ensiling process, and the effect of two different bacterial inoculants as compared with the uninoculated natural epiphytic fermentation on the distribution of the fungi associated with the silage. The fungal community from duplicate mini-silo packages of the same treatment was analyzed by denaturing gradient gel electrophoresis and direct sequencing of the resulting operational taxonomic units. This method proved useful in analyzing the complex microbial communities associated with the forage in that it was possible to determine that one inoculant dramatically influenced the fungal community associated with whole plant corn silage.
Significant portions of grain produced for livestock consumption are convened into ensiled forage. Silage producers have long recognized the positive effects of using an inoculant to insure the proper transformation of forage into a palatable and digestible feedstuff. When silage is fed from a storage structure, exposure to air stimulates the growth of epiphytic aerobes that may result in the loss of up to 50% of the dry matter. Moreover, fungi have been found to be associated with ensiled forage, but their growth is normally suppressed by the anaerobic conditions. However, the introduction of oxygen results in a fungal bloom, and the fungi and the associated metabolites may result in lost productivity in the livestock consuming the contaminated forage. In this study, we report on the diversity of the fungal community associated with whole plant corn silage during the ensiling process, and the effect of two different bacterial inoculants as compared with the uninoculated natural epiphytic fermentation on the distribution of the fungi associated with the silage. The fungal community from duplicate mini-silo packages of the same treatment was analyzed by denaturing gradient gel electrophoresis and direct sequencing of the resulting operational taxonomic units. This method proved useful in analyzing the complex microbial communities associated with the forage in that it was possible to determine that one inoculant dramatically influenced the fungal community associated with whole plant corn silage.
Kurochkin IO, Ivanina AV, Eilers S, Downs CA, May LA, Sokolova IM. Cadmium affects metabolic responses to prolonged anoxia and reoxygenation in eastern oysters (Crassostrea virginica). Am J Physiol Regul Integr Comp Physiol 297: R1262-R1272, 2009. First published September 2, 2009 doi:10.1152/ajpregu.00324.2009.-Benthic marine organisms such as mollusks are often exposed to periodic oxygen deficiency (due to the tidal exposure and/or seasonal expansion of the oxygen-deficient dead zones) and pollution by metals [e.g., cadmium, (Cd)]. These stressors can strongly affect mollusks' survival; however, physiological mechanisms of their combined effects are not fully understood. We studied the effects of Cd exposure on metabolic responses to prolonged anoxia and subsequent recovery in anoxia-tolerant intertidal mollusks Crassostrea virginica (eastern oysters). Anoxia led to an onset of anaerobiosis indicated by accumulation of L-alanine, acetate, and succinate. Prolonged anoxia (for 6 days) caused a decline in the maximum activity of electron transport chain and ADP-stimulated (state 3) oxygen uptake by mitochondria (MO 2), but no change in the resting (state 4) MO 2 of oyster mitochondria, along with a slight but significant reduction of mitochondrial respiratory control ratio. During reoxygenation, there was a significant overshoot of mitochondrial MO 2 (by up to 70% above the normoxic steady-state values) in control oysters. Mild mitochondrial uncoupling during prolonged shutdown in anoxic tissues and a subsequent strong stimulation of mitochondrial flux during recovery may help to rapidly restore redox status and protect against elevated reactive oxygen species formation in oysters. Exposure to Cd inhibits anaerobic metabolism, abolishes reoxygenation-induced stimulation of mitochondrial MO 2, and leads to oxidative stress (indicated by accumulation of DNA lesions) and a loss of mitochondrial capacity during postanoxic recovery. This may result in increased sensitivity to intermittent hypoxia and anoxia in Cd-exposed mollusks and will have implications for their survival in polluted estuaries and coastal zones. air exposure; recovery; mitochondrial function; oxidative damage; mollusks PERIODICAL OXYGEN DEFICIENCY is an important environmental stressor in intertidal and coastal habitats. Short-term intermittent hypoxia/anoxia (from several hours to several days, depending on the state of the tides) often occurs in intertidal invertebrates during the low tide, and may also occur in tidal pools and shallow lagoons with limited water exchange (8,36,49). Furthermore, long-term severe hypoxia and anoxia triggered by anthropogenic release of nutrients has become a serious issue in many estuaries and coastal zones rivaling the climate change (18,22). In the coastal dead zones, benthic invertebrates including mollusks can be exposed to severe hypoxia or anoxia for prolonged periods (from weeks to up to several months) (10,22,34,46). Long-term oxygen deficiency often leads to the massive die-offs in species with limited or...
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