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We examined photopigment degradation and transformation in sediment microcosms that received different detrital source materials (planktonic, littoral, terrestrial) in the presence or absence of amphidpods (Gammarus sp.). Additions of realistic quantities of particulate organic matter resulted in detectable changes in pigment concentration and composition despite insignificant changes in total organic matter. The transformation of chlorophyll a to total phaeophorbide was significantly higher in all high quality (high nitrogen) detritus treatments containing amphipods. The highest production of phaeophorbide was in the higher quality detritus (blue-green algae, Anabaena cylindrica, and macrophyte, Vallisneria americana) when compared to red maple (Acer rubrum). Phaeophytin formation was not related to amphipod grazing and thus may be determined more by microbial heterotrophic processes. The degradation product of the carotenoid lutein, lutein 5,6 expoxide, was formed in all treatments. Phaeopigment composition can be used to infer differences in heterotrophic activity and will help in the interpretation of photopigment distribution in field samples. 相似文献
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《Animal : an international journal of animal bioscience》2019,13(5):968-974
Stressful situations may result in serum chromium (Cr) depletion with increased urinary excretion of the mineral and increased Cr requirements. The objective of this study was to investigate the effects of Cr supplementation on growth performance, feeding behavior, blood metabolites and hormones, indicators of oxidative stress and glucose-insulin kinetics of summer-exposed weaned dairy calves. In total, 48 Holstein female calves (63 days of age; 77.0±1.45 kg of BW) were assigned randomly to one of two treatments: (1) a control group with no supplemental Cr (Cr−), and (2) a supplemental Cr group (Cr+) to supply 0.05 mg Cr as Cr-methionine/kg of BW0.75. Chromium was provided in the starter feed and adjusted weekly based on BW over the experimental period. All calves were on experiment for 4 weeks after weaning. The average maximum temperature–humidity index was 76.1 units during the study period, indicating a mild degree of environmental heat load. Results indicated that in summer-exposed dairy calves, increased dietary Cr provision tended to decrease fecal score, tended to change rumination pattern, increased antioxidant capacity by increasing serum concentration of catalase, but had no effects on growth performance, metabolic status or peripheral glucose and insulin metabolism. 相似文献
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