Browsing by Subject "Amino acid"

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Effects of elevated atmospheric CO2 concentrations on insects and pathogens of spring wheat (Triticum aestivum L. cv. Triso) and oilseed rape(Brassica napus cv. Campino)
(2012) Oehme, Viktoriya; Fangmeier, Andreas
It is suggested that plants, herbivore insects and pathogens will be affected by rising atmospheric CO2. The working hypothesis of this study was that elevated CO2 will affect plant composition and will thus exert influence on plant-insect interactions by changing the nutritive value for insects feeding on phloem sap. To test this hypothesis, experiments were carried out on wheat and oilseed rape in two different systems: controlled environment chambers (climate chamber system) and an open field exposure system with natural climatic and soil conditions (Mini FACE system). The abundance of detrimental insects from different feeding guilds and plant damage by parasitic organisms were examined in a Mini FACE system, while the consequences of elevated CO2 on aphid performance and potential correlations to phloem sap composition of host plants were observed in controlled environment chambers. The concentrations of amino acids and carbohydrates in the phloem of host plants were analysed by high?performance liquid chromatography (HPLC), using a fluorescence detector for amino acids and the evaporative light scattering detector for carbohydrates. In a Mini-FACE system, phenological development of spring wheat and OSR was not significantly changed due to CO2 enrichment. However, elevated CO2 induced changes in plant chemistry (increased carbon:nitrogen ratio and defensive compounds), which resulted in changes in population densities of some pest species. In order to monitor alterations in insect population density, two different methods were applied: direct counts (method 1) and using of yellow sticky traps (method 2). These methods showed both increases and decreases of insect numbers due to elevated CO2, depending on species and on the period of observation. Concerning plant pathogens, leaves of spring wheat were only slightly and not significantly damaged by Erysiphe graminis, Puccinia striiformis, Puccinia recondita and Septoria tritici during the 2006/2008 years in all treatments. Also the OSR was not significantly damaged by Peronospora parasitica. The frequency and severity of disease infestation on spring wheat and OSR was not significantly impacted by elevated CO2. In controlled-environment chambers, the phenology, above ground biomass and RGR of OSR were not significantly impacted due to elevated CO2. And although the phenology of spring wheat was not influenced by raised CO2, significant increases were observed for plant above ground biomass and RGR. The aphid presence significantly reduced the aboveground biomass and RGR of spring wheat, while no effects due to aphids were observed in OSR. High-CO2 treatment differently impacted the performance of aphids. Slight and non-significant increases due to elevated atmospheric CO2 conditions were observed for the aphid relative developmental stages and intrinsic rates of increase, while the weight and RGR were significantly increased for Rhopalosiphum padi and decreased for Myzus persicae. In order to clear CO2-impacts on the insect performance, phloem sap from host plants was analysed for the composition and concentration of amino acids and carbohydrates. In summary, although the phenological development of spring wheat and OSR was not affected due to elevated CO2, significant changes were found for the concentration of carbohydrates in the phloem sap of spring wheat and individual amino acids in both host plants. These alterations in plant chemistry affected the performance and abundance of herbivore insects.
Escherichia coli O157:H7 und seine Adaption an verschiedene Wachstumsbedingungen in vitro : Untersuchung des intrazellulären Proteoms und Kohlenhydratmetabolismus
(2014) Polzin, Sabrina; Schmidt, Herbert
The aim of this study was to investigate the linkage of metabolism and pathogenicity of EHEC bacteria under certain environmental conditions in vitro. During the investigations the influence of environmental conditions could be shown on the protein as well as on the gene expression level. In experiments using the culturel media SIEM and SCEM compared to TSB as a reference, differential expression of proteins and genes were shown. For example, decreasing motility and the formation of biofilm-like substances were observed. Furthermore, differences in metabolism and expression of chaperons and stress response systems were detected. After culturing EHEC bacteria in experimental media, increased glucose and pyruvate metabolism, increased amino acid biosynthesis, as well as increased chaperon levels were found, in contrast to decreased expression levels of stress associated proteins. The experimental procedure also affected the presence of pathogenicity factors, like EspP and EspB. Notably, the environmental conditions induced the glutamic acid resistance, providing the EHEC bacteria an unhindered passage through the human gastrointestinal tract, especially the acidic environments like the stomach. Additionally, the sialic acid esterase Z1466 along with shiga toxin, was strongly expressed. This could provide an advantage over the intestinal micro flora, in respect of growth. Effects onto glucose metabolism and amino acid biosynthesis were investigated by isotopoloque profiling experiments, prepared thankworthy by Dr. rer. nat. Wolfgang Eisenreich (Munich). To conclude, stress response and expression of pathogenicity factors could be induced in vitro in the cultural media elected, and without the need of a human host. The experiment also advices the complex regulation of different processes in bacterial cells as response to external factors.
Factors influencing the response of broiler chicken to glycine supplements in low crude protein diets
(2016) Siegert, Wolfgang; Rodehutscord, Markus
The increasing demand for meat and other animal products along with the global limitation of arable land for crop production is expected to result in a shortage of protein-rich feedstuff. Furthermore, the excretion of nitrogenous compounds has negative effects on the environment because of the risk of nitrogen (N) leakage into the groundwater. Ammonia emissions from livestock enterprises have been associated with environmentally damaging effects. The biggest determinant of ammonia emissions associated with livestock farming is excretion of N. Excretion of N in part is inevitable but N excretion can be reduced by avoiding excessive intake of feed protein. At present, there is a substantial lack of knowledge about the requirement of nitrogenous nutrients except for essential amino acids (AA) and the influence of these nutrients on animal physiology. As reported in the literature, this has often led to undesirable effects of low crude protein (CP) diets on growth. This partly is due to a deficient glycine (Gly) and serine (Ser) supply in low CP diets. This thesis focused on factors influencing the response to Gly and Ser in low CP broiler feed because growth response to these AA was inconsistent in the literature. In the first study, a meta-analysis was conducted to investigate the response of broilers to dietary levels of Gly equivalents (Glyequi) of Gly and Ser in existing literature. A curvilinear relationship between Glyequi and daily gain (ADG), daily feed intake (ADFI) and feed efficiency (G:F) was found. The impact of dietary Glyequi on ADFI was low, but G:F and ADG varied markedly at different levels of Glyequi. The effect of dietary Glyequi depended on the supply of both methionine (Met) and cysteine (Cys). The G:F and ADG response to dietary Glyequi was different for different Met:(Met+Cys) ratios and Cys concentrations. This was explained by a decreased necessity of conversion of Met to Cys, for which Ser is needed. Adequate concentrations of both Met and Cys probably reduced the necessity of the conversion of Met to Cys. The second study investigated the effect of threonine (Thr) and choline, which are endogenous precursors of Gly, on the response to dietary Glyequi. An increase in Thr concentration reduced the Glyequi concentration required to achieve certain response levels of G:F and ADG. Choline also exerted a considerable effect, but the Glyequi replacing effect of choline was less pronounced than Thr. The observed replacement values of dietary Thr and choline for dietary Glyequi exceeded the possible replacement values calculated by considering endogenous conversion. This likely originated from an excess supply of other essential AA than Thr. If Thr and, to a lower extent, choline limited growth, then excessive intake of other AA had to be catabolized, resulting in an increased need for Glyequi for uric acid formation. It was concluded that further studies should take Glyequi, choline, and Thr together into consideration when determining the requirements for these nutrients. The third study aimed to investigate whether the growth performance and N utilization of broilers are influenced by different proportions of free and peptide-bound AA in diets, and if his influences Glyequi requirements. The hypothesis was that an increased oxidation of free AA leads to an increased ammonia production, which must be detoxified to uric acid in a Gly-dissipating process. 2×2 factorial arrangements were used where one factor was AA from soy protein isolate or from a free AA mix. The other factor was a low and high level of Glyequi. Replacing AA from the soy protein isolate with free AA reduced ADG and G:F, mainly due to reduced ADFI. Reasons for that cannot be identified clearly. The N efficiency on day 21 was not different between the AA sources, possibly due to the lower AA digestibility of the soy protein isolate and higher urinary excretion of nitrogenous substances in the treatments with the AA mix. Thus, availability of AA for protein synthesis after ingestion probably did not limit broiler growth. The ADG of the treatments with the high Glyequi concentration was higher for both AA sources. This increase was due to higher ADFI by broilers in the treatments with soy protein isolate and due to the increased G:F in the treatments with the AA mix. Contrary to the hypothesis, these responses did not give an indication of different utilization of Glyequi for uric acid synthesis. In conclusion, the response of broiler chicken to dietary Glyequi depends on other dietary characteristics, like the concentrations of Cys, Thr, and choline. The information described in this thesis contribute to enable further optimization of the dietary Glyequi concentration as well as the other dietary characteristics influencing the response to Glyequi. This enables reducing the CP concentration in diets without adverse effects on growth and, therefore, diminishing the negative effects of broiler production on the environment.
Morphological and chemical plant properties mediate host plant selection of whiteflies (Hemiptera: Aleyrodidae)
(2021) Stoll, Nina Sara; Zebitz, Claus P. W.
Whiteflies are among the most important pests causing severe damage to numerous cultivated and ornamental plants worldwide. The present dissertation comprises four studies and contributes to the knowledge of the host plant selection process by whiteflies. In the first study, host preferences were determined in dual choice tests for Aleyrodes proletella (L.), Bemisia tabaci (Genn.), and Trialeurodes vaporariorum (Westw.) on several host plants. On the one hand, this study extends the knowledge on the food spectrum of these economically important pests; on the other hand, the results highlight the host adaptation of whiteflies. The second study elucidated potential sources of host plant resistance against A. proletella, B. tabaci, and T. vaporariorum by recording their probing and feeding behaviour on two host plants each using the electrical penetration graph (EPG) method. It is concluded that whiteflies decide upon host plant acceptance by evaluation of multiple plant factors located in epidermal and/or mesophyll tissues of leaves as well as in the phloem sap of plants. Moreover, epicuticular leaf waxes are a key factor in the host selection process of A. proletella. It is hypothesized that constituents of the leaf surface wax act as stimulants promoting leaf penetration and phloem accession. The findings of this study shed light on the whitefly-host adaptation. The goal of the third study was to identify the role of epicuticular leaf waxes of several Brassica cultivars in the host selection process of A. proletella. For this purpose, dual choice tests were carried out on both waxy and dewaxed plant leaves as well as on Parafilm® treated with different leaf wax extracts. Also, life-history traits were monitored on waxy and dewaxed leaves, and the feeding activity of A. proletella was recorded on Parafilm® with and without leaf wax extracts. Scanning electron microscopy (SEM) imaging was used to visualize epicuticular leaf waxes on the plant surface. Finally, it was proved that leaf surface waxes of host plants promote feeding and act as phagostimulants. Although the wax compounds mediating host plant selection remain unknown, these findings offer breeding potential for resistant crop cultivars. In the fourth study, the influence of free phloem amino acids on the host plant selection of T. vaporariorum was investigated. Via liquid chromatography-mass spectrometry (LC-MS), the amino acid profiles in the phloem sap of six vegetable crops varying in their host plant attractiveness were analysed. Subsequently, stepwise multiple regressions of the relative amino acid compositions and the pre-determined host plant preferences were performed. To verify the contribution of single amino acids on host choice, dual choice tests on sucrose media with and without added single amino acids were carried out. Single amino acids play an active role in phagostimulation, whereas some amino acids exert strong inhibitory effects. This indicates that the dominant presence of such amino acids might reduce phloem sap uptake, thus contributing to host plant resistance towards T. vaporariorum. Overall, this research compared the host selection process of three whitefly species to identify their underlying mechanisms. It is hypothesized that the observed host selection strategies are the result of evolutionary adaptations between whiteflies and their host plants. Depending on the occupied ecological niche, species-specific host plant ranges of varying complexity were formed. Accordingly, the host selection process of the more specialised species A. proletella is particularly efficient by consideration of characteristic leaf surface wax stimuli. In contrast, host selection of the extreme generalists B. tabaci and T. vaporariorum is regulated by simple gustatory stimuli in order to take advantage of the host diversity they are offered. The findings of this research provide the basis for new approaches to optimizing breeding programs for whitefly resistant crops.
Variability of the protein and energy values of European dried distillers´ grains with solubles for ruminants
(2013) Westreicher Kristen, Edwin; Rodehutscord, Markus
The increasing demand of energy together with the implementation of the European Program for the use of energy from renewable sources are favourable scenarios to increment the ethanol production in the coming years in the EU. Ethanol production yields dried distillers´ grains with soluble (DDGS) as the main by-product, a valuable feedstuff for ruminants. A great number of publications mainly form USA and Canada has demonstrated the great variability of the feed value of corn-DDGS, the main by-product from ethanol production in these countries. In the EU, different and diverse technological conditions predominate and little was investigated to evaluate the feed value of DDGS. The variability of feeding value in conjunction with expected increase of DDGS production demands for further and more specific characterization of this by-product in the EU. Therefore, a project was conceived to characterize the chemical composition and evaluate the protein and energy value for ruminants of DDGS from different European countries. Thirteen samples of DDGS originating from wheat, corn, barley, and blends of different substrates were used. In the first study, the objective was to characterize variations in the composition and nutritive value of DDGS, and to estimate the undegradable crude protein (UDP) in DDGS. The rumen degradation of crude protein (CP) was determined using the nylon bag technique. Samples were incubated for 0, 1, 2, 4, 8, 16, 32, and 72 h, and in situ degradation kinetics were determined. UDP was estimated using a passage rate of 8 %/h. In vitro gas production was measured to estimate the metabolizable energy (ME), net energy for lactation (NEL) and in vitro digestibility of organic matter (IVDOM). Chemical profiles varied among samples (in g/kg dry matter (DM) ± standard deviation, the values were 310 ± 33 CP, 86 ± 37 ether extract, 89 ± 18 crude fibre, 408 ± 39 neutral detergent fibre, 151 ± 39 acid detergent fibre, and 62 ± 31 acid detergent lignin), as well as in protein fractions according to the Cornell Net Carbohydrate and Protein System (in g/kg CP, the values were 161 ± 82 for fraction A, 24 ± 11 for fraction B1, 404 ± 105 for fraction B2, 242 ± 61 for fraction B3, and 170 ± 87 for fraction C). ME, NEL (MJ/kg DM) and IVDOM (%), also varied among samples: 12.1 ± 0.59, 7.3 ± 0.39, and 72.5 ± 4.30, respectively. The in situ rapidly degradable CP fraction (a) varied from 10.2 to 30.6%, and the potentially degradable fraction (b) averaged to 66.8%. UDP varied from 8.6 to 62.6% of CP. This first study suggests significant variations in composition and nutritive value among different sources of DDGS. UDP could be predicted on the basis of analysed CP fractions, but the accuracy of UDP prediction improved upon the inclusion of neutral-detergent insoluble nitrogen, explaining 94% of the variation in the UDP values. To conclude, chemical protein fractions may be used to predict the UDP values of DDGS and the variability in the protein fractions of DDGS should be considered when formulating diets for dairy cows. To provide additional information on the nutritional value of DDGS, a second study was carried out to determine and compare the in situ ruminal degradation of CP and amino acids (AAs) of DDGS and to characterize the in vitro pepsin-pancreatin solubility of CP (PPS) from dietary DDGS (d-DDGS) and DDGS residue (DDGS-r) obtained after 16-h ruminal incubation. The rumen degradation of AAs and CP was determined using nylon bag incubations in the rumen of cows. Lysine and methionine content of d-DDGS varied from 1.36 to 4.00 and 1.34 to 1.99 g/16 g N, respectively. The milk protein score (MPS) of d-DDGS was low and ranged from 0.36 to 0.51, and lysine and isoleucine were estimated to be the most limiting AAs in d-DDGS and DDGS-r. DDGS-r contained slightly more essential AAs than did the d-DDGS. Rumen degradation of CP after 16 h varied from 44% to 94% between DDGS samples. Rumen degradation of lysine and methionine ranged from 39% to 90% and from 35% to 92%, respectively. Linear regressions showed that ruminal degradation of individual AAs can be predicted from CP degradation. The PPS of d-DDGS was higher than that of DDGS-r and it varied from 70% to 89% and from 47% to 81%, respectively. There was no significant correlation between the PPS of d-DDGS and PPS of DDGS-r (R2 = 0.31). The estimated intestinally absorbable dietary protein (IADP) averaged 21%. Moderate correlation was found between the crude fibre content and PPS of DDGS-r (R2 = 0.43). This study suggests an overestimation of the contribution of UDP of DDGS to digestible protein supply in the duodenum in currently used protein evaluation systems. More research is required and recommended to assess the intestinal digestibility of AAs from DDGS. Finally, in a third study, three sources of DDGS were evaluated in diets of mid-lactating dairy cows on milk production and milk composition and on digestibility in sheep. DDGS from wheat, corn and barley (DDGS1), wheat and corn (DDGS2) and wheat (DDGS3) were studied and compared with a rapeseed meal (RSM). RSM and DDGS were characterized through in situ CP degradability. Nutrient digestibility was determined in sheep. Twenty-four multiparous cows were used in a 4 × 4 Latin square design with 28-day periods. Treatments included total mixed rations containing as primary protein sources RSM (control), DDGS1 (D1), DDGS2 (D2) or DDGS3 (D3). RSM contained less rapidly degradable CP (fraction a), more potentially degradable CP (fraction b) and more UDP than the three DDGS. In vivo organic matter digestibility of RSM was similar to DDGS. Calculated NEL was lower for RSM (7.4 MJ/kg DM) than for DDGS, which averaged 7.7 MJ/kg DM. Cows? dry matter intake did not differ between diets (21.7 kg/d). Cows fed D1 yielded more milk than those fed D3 (31.7 vs. 30.4 kg/d); no differences were found between control and DDGS diets (31.3 vs. 31.1 kg/d). Energy-corrected milk was similar among diets (31.2 kg/d). Diets affected neither milk fat concentration (4.0%) nor milk fat yield (1.24 kg/d). Milk protein yield of control cows (1.12 kg/d) was significantly higher than D3 (1.06 kg/d) but not different from D1 and D2 (1.08 kg/d each). Feeding DDGS significantly increased milk lactose concentration (4.91%) compared to control (4.81%). DDGS can be a suitable feed compared to RSM and can be fed up to 4 kg dry matter per day in rations of dairy cows in mid-lactation. To conclude, DDGS is a suitable feedstuff for ruminants in terms of chemical composition, energy and protein value. However, the variability should be considered when included in diets of ruminants, especially in animals with high performance. For this purpose, prediction approaches initated in this study should be further developed into tools for routine application for rapid DDGS evaluation and estimation of feed values. These approaches might also be usefull for the evaluation of other feed protein sources and taked into consideration for practical feeding and diets formulation.