Mutton meat was tested in different products in order to obtain prototype products in which mutton can effectively be used without the objectionable mutton off flavor. Mutton flavor reduction was achieved in the processed meat products by: (a) lowering mutton fat to a level of 10% or less, (b) using spices, smoking and/or curing, (c) substituting fat from beef or pork for mutton fat, and (d) the action of microbial starter cultures. Four taste panel sessions were set up to rate these products against an all beef or all pork control for consumer acceptability. Taste panel results indicate that flavor had the greatest effect on overall acceptability of these products, compared to texture and appearance. Proximate meat analysis for fat, protein, moisture and ash were performed using the Technicon InfraAlyzer 400R and the results were compared with values obtained by reference AOAC methods. Correlation coefficients of 0.992, 0.867, 0.992 and 0.511 were obtained for fat, protein, moisture and ash respectively. The two methods were not significantly different (p = .05). These results indicate that the InfraAlyzer may be used as a rapid method for proximate analysis of fat, protein and moisture.

In a series of indoor and outdoor experiments with young sheep, feed supplements having different protein content were investigated. The supplements were chosen as those likely to elicit different Protein:Energy (P/E) ratios in the nutrients absorbed by the animal. The objective was to identify and characterize those that would support faster growth rate, bigger and leaner carcass production for the meat market, in different seasons in Southern Victoria, Australia (35-37° South, 141-143° East). Throughout, the GrazFeed model provided a reference system chosen for prediction of performance, with which the results of grazing experiments could be compete. / Supplementary feeding experiments were undertaken in the field (Experiments 1 and 4) in seasonal periods in which the pasture base found to poorly support high growth rates of weaned lambs. These experiments were supported by nutritional studies in pens (Experiments 2, 3 and 5) and supplement effects were evaluated in terms not only of liveweight but carcase and meat characteristics. Supplements used were evaluated and selected for use in further experiments on the basis that they would provide additional metabolisable energy but also would differ in the amount and nature of the crude protein they supplied and thus deliver different balances of absorbed nutrients, in particularly different P:E ratios. / Fish meal, with a high content of rumen undegradable protein of high biological value was used in each of these experiments to provide a test of the hypothesis that slow ruminal degradation and additional protein digested in the small intestine can influence animal response. In Experiment 1 and the related pen Experiment 2, comparing a lower to a higher P (CP%):E(MJ/kg) ratio feeds (barley, 12:13 P:E ratio) to (fishmeal / lucerne meal, 1/2 w/w, 35:10 P:E ratio), barley resulted in higher fat and lower protein amounts deposited as carcass components (P<0.01). The animals consuming extra protein were larger, leaner and became more uniform as a flock in terms of the range in LW and fat content at slaughter than those provided with supplements that are classed as energy feeds. / In Experiment 3 a range of alternative protein rich feeds and composite supplements was assembled that are cheaper and more readily available than fishmeal, with the idea that different patterns of ruminal degradation, intra-ruminal N availability and amounts of RUP could be created that would be beneficial in terms of the overall animal response. The paths of rumen protein degradability was determined with nylon bag techniques, and this was used to select feeds for investigation in a field and indoor experiments, Experiments 4 and 5. / In Experiment 4, grazing animals supplemented with lupines; (P:E 32:12), fishmeal / wheat bran 1/2 w/w (P:E 35:12) and formaldehyde treatment protected sunflower meal / wheat bran 1/2 w/w (P:E 24:11) responded poorly to the supplements where quality and quantity of pasture was such that unsupplemented growth rates were predicted to be poor by the decision support model, GrazFeed. In this and the supporting pen Experiment 5, the liveweight gain, final weight and dressing percentage of all supplemented lambs were significantly better than those of control (grazing only) animals (P<0.05). High and low commencing LW animals responded to protein supplements differently when these were fed at 1% BW with ad libitum medium quality roughage diet in indoor conditions. The heavier subgroup of fish meal / wheat bran (P:E 35:12) animals were significantly fatter than the heavy subgroup of wheat bran (P:E 17:10) animals (P<0.001). Lighter subgroup of animals were leaner and became more uniform (less variable) in weight and composition as a flock. Both the heavy and the light liveweight subgroups of fish meal grew faster but were fatter at slaughter than any other sub-groups. Lightest lambs fed bran grew from 26 to 36 kg in 10 weeks and had the most suitable carcase with the lowest priced supplement tested in the experiment. / Though protein supplementation had a positive effect on lamb performance; the advantage of high RUP was not consistent or always statistically significant. Compared to the alternative protein rich feeds, fish meal showed no cost effective advantage. The consequence of this current or possible future market conditions for feeding strategies for high quality lamb production are considered.

Cette thèse est une contribution au développement d'un procédé tactile acoustique basé sur la perturbation des ondes de Lamb, permettant de détecter un toucher simple ou des touchers multiples sur des objets minces de forme quelconque. Après avoir étudié la propagation des modes de Lamb dans les objets minces par exemple les plaques de cuivre d'épaisseur 450 µm, nous avons observé, que l'énergie des ondes de Lamb antisymétriques était essentiellement due à la composante normale de déplacement et qu'il était aisé de perturber un mode de flexion par un toucher surfacique réalisé avec le doigt ou ponctuel avec la pointe d'un stylo, tandis que dans le cas d'un mode symétrique, l'énergie était essentiellement distribuée sur la composante de déplacement tangentielle et en conséquence plus difficilement perturbée par une interaction tactile. Nous avons en conséquence exploité le toucher sur une plaque mince perturbant le rayonnement d'une onde acoustique dans l'objet et réalisé en pratique une mesure de la perturbation d'un signal de diffraction des ondes de Lamb en un ou deux points récepteurs d'une plaque. Ainsi, une méthode de localisation basée sur la diffraction des ondes a été proposée, pour obtenir une interface tactile compacte, performante et faible coût. Cette méthode nommée méthode de la Figure de Diffraction Perturbée en Amplitude (FDPA) peut rendre une surface tactile avec une résolution spatiale de l'ordre du millimètre et un temps de réponse inférieur à 10 ms. Deux méthodes d'optimisation sont proposées pour obtenir un taux de localisation correcte proche de 100%. Le procédé tactile et les méthodes d'optimisation présentés dans cette thèse ont été testés sur plusieurs types d'objets, réalisés dans des matériaux différents et sous différentes formes géométriques. Ces réalisations ont montré des performances satisfaisantes en termes d'encombrement, de consommation et de fiabilité de localisation pour des touchers simples et multiples.

Today’s MEMS technology allows manufacturing of miniaturized, low power sensors that sometimes exceeds the performance of conventional sensors. The pressure sensor market today is dominated by MEMS pressure sensors. In this thesis two different pressure sensor techniques are studied. The first concerns ways to improve the sensitivity in the most commonly occurring pressure sensor, namely such based on the piezoresistive technique. Since the giant piezoresistive effect was observed in silicon nanowires, it was assumed that a similar effect could be expected in nano-thin silicon films. However, it turned out that the conductivity was extremely sensitive to substrate bias and could therefore be controlled by varying the backside potential. Another important parameter was the resistivity time drift. Long time measurements showed a drastic variation in the resistance. Not even after several hours of measurement was steady state reached. The drift is explained by hole injection into the buried oxide as well as existence of mobile charges. The piezoresistive effect was studied and shown to be of the same magnitude as in bulk silicon. Later research has shown the existence of such an effect where the film thickness has to be less than around 20 nm.  The second area that has been studied is the pressure sensitivity of in acoustic resonators. Aluminium nitride thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes have been theoretically and experimentally studied in a comparative manner. The S0 Lamb mode is identified as the most pressure sensitive FPAR mode. The theoretical predictions were found to be in good agreement with the experiments. Additionally, the Lamb modes have been tested for their sensitivities to mass loading and their ability to operate in liquids, where the S0 mode showed good results. Finally, the pressure sensitivity in aluminium nitride thin film bulk wave resonators employing c- and tilted c-axis texture has been studied. The c-axis tilted FBAR demonstrates a substantially higher pressure sensitivity compared to its c-axis oriented counterpart.

Au cours de ces travaux, nous avons effectué une étude théorique et expérimentale d'un dispositif destiné à la génération et détection des ondes de Lamb sur un substrat non piézoélectrique, avec pour objectif des applications industrielles, parmi elles la mesure de densité de liquide en continu. Ce dispositif est constituée de deux lames piézoélectriques identiques à base de P(VF2-VF3) et d'épaisseur 110~m, posées sur un substrat en aluminium d' épaisseur 90~. Sur chaque lame est gravé un réseau d'électrodes métalliques. La présence d'un liquide sur un coté du substrat change la fréquence de synchronisme du dispositif. Pour mesurer cette variation de la fréquence de synchronisme, nous avons développé un système électronique dédié au contrôle de la génération et de l'acquisition du signal. La modélisation complète du dispositif, qui comprend la génération, la propagation et la détection de l'onde, nous a pennis de relier la variation de la fréquence de synchronisme mesurée avec la densité du liquide en contact avec la plaque. Si la vitesse longitudinale dans le liquide en contact avec la plaque est connue, nous pouvons donc utiliser ce dispositif pour mesurer la densité absolue des liquides avec une incertitude d'environ 5%.

Ce travail de recherche est dédié à la simulation de la réponse transitoire des assemblages de poutres soumis à des chocs. De tels chargements entraînent la propagation d'ondes haute fréquence dans l'ensemble de la structure. L'énergie qu'elles transportent peut être dommageable pour son fonctionnement ou celui des équipements embarqués. Dans des études précédentes, il a été observé sur des structures expérimentales qu'un régime vibratoire diffusif tend à s'installer pour des temps longs. Le but de cette étude est donc de développer un modèle robuste de la réponse transitoire des assemblages de poutres soumis à des chocs permettant de simuler, entre autres, cet état diffusif. Les champs de déplacement étant très oscillants et la densité modale élevée, la simulation numérique de la réponse transitoire à des chocs peut difficilement être menée par une méthode d'éléments finis classique. Une approche utilisant un estimateur de la densité d'énergie de chaque mode de propagation a donc été mise en œuvre. Elle permet d'accéder à des informations locales sur les états vibratoires, et de contourner certaines limitations intrinsèques aux longueurs d'onde courtes. Après avoir comparé plusieurs modèles de réduction cinématique de poutre à un modèle de Lamb de propagation dans un guide d'ondes circulaire, la cinématique de Timoshenko a été retenue afin de modéliser le comportement mécanique haute fréquence des poutres. En utilisant ce modèle dans le cadre de l'approche énergétique évoquée plus haut, deux groupes de modes de propagation de la densité d'énergie vibratoire dans une poutre ont été isolés : des modes longitudinaux regroupant un mode de compression et des modes de flexion, et des modes transversaux regroupant des modes de cisaillement et un mode de torsion. Il peut être également montré que l''evolution en temps des densités d'énergie associées obéit à des lois de transport. Pour des assemblages de poutres, les phénomènes de réflexion/transmission aux jonctions ont du être pris en compte. Les opérateurs permettant de les décrire en termes de flux d''energie ont été obtenus grâce aux équations de continuité des déplacements et des efforts aux jonctions. Quelques caractéristiques typiques d'un régime haute fréquence ont été mises en évidence, tel que le découplage entre les modes de rotation et les modes de translation. En revanche, les champs de densité d'énergie sont quant à eux discontinus aux jonctions. Une méthode d'éléments finis discontinus a donc été développée afin de les simuler numériquement comme solutions d''equations de transport. Si l'on souhaite atteindre le régime diffusif aux temps longs, le schéma numérique doit être peu dissipatif et peu dispersif. La discrétisation spatiale a été faite avec des fonctions d'approximation de type spectrales, et l'intégration temporelle avec des schémas de Runge-Kutta d'ordre élevé du type "strong stability preserving". Les simulations numériques ont donné des résultats concluants car elles permettent d'exhiber le régime de diffusion. Il a été remarqué qu'il existait en fait deux limites diffusives différentes : (i) la diffusion spatiale de l''energie sur l'ensemble de la structure, et (ii) l'équirépartition des densités d'énergie entre les différents modes de propagation. Enfin, une technique de renversement temporel a été développée. Elle pourra être utile dans de futurs travaux sur le contrôle non destructif des assemblages complexes et de grandes tailles.

Nondestructive testing (NDT) uses different wave propagation modes to evaluate the internal structure of materials, revealing internal damage such as corrosion and fracturing that cannot be detected by traditional methods. Civil infrastructures are considered high priority assets in Ontario and Canada because of their value, high consequence of failure, and the continual influence of aging effects. Unexpected failure of infrastructure not only costs more than planned replacements but also results in increased safety risks. The in-situ condition assessment of civil infrastructure is critical for the successful implementation of maintenance and safety programs. Therefore, reliable nondestructive methods of inspection are required for the implementation of economical and efficient maintenance and asset management programs. Continuing technological developments in data collection, acquisition equipment, and data processing techniques have provided useful applications of nondestructive methods in many engineering fields. Among the many applications, this research study examines three applications of nondestructive testing in civil engineering: (1) condition assessment of construction joints in asphalt pavements, (2) average thickness evaluation of steel pipes, and (3) void and debonding detection in grouted steel tanks. The study on asphalt focuses on the improvement of the coupling system between the transducers and the asphalt surface, and the development of a new data processing technique to reduce user input and increase the reliability of the condition assessment of longitudinal joints. The current wavelet transmission coefficient (WTC) method requires user input, making the automatic data processing difficult. In the WTC method, the coupling between the transducers and the asphalt surface requires the use of epoxy and aluminum plates. This procedure is not practical for testing in-service roads. A new coupling mechanism using polyurethane foam to provide a spring action on the transducers and calibrated weights to generate a compression force was developed and showed good results, reducing the testing time by up to 50%. A new and robust data analysis methodology, called instantaneous transmission coefficient (ITC), is proposed based on measured instantaneous frequencies and damping ratios. The main advantage of the ITC procedure is that it can be performed automatically, reducing user input. A laboratory scale asphalt slab is used to evaluate the new methodology. Results show good agreement between the WTC and ITC measurements for both jointed and joint-free areas. The second study investigates the feasibility of the multichannel analysis of surface waves (MASW) technique for the evaluation of the average wall thickness of steel pipes. Electromagnetic NDT methods, such as the eddy current and the remote field testing, are common tools for thickness measurement of conductive materials. However, these methods give only localized results where measurements are made, making the process time consuming and inaccurate for assessing the full cross-sectional area of the pipe. Lamb waves have been used previously in the evaluation of steel pipes; however, the existing techniques require prior calibration to a theoretical wave mode, and their accuracy decreases with the length of the pipe evaluated due to wave attenuation effects. Preliminary results show the capability of the MASW test for providing reliable thickness information. The measured dispersion curves include information of fundamental modes and the higher modes, providing an improved characterization of the medium. Thicknesses between 3.2 mm and 12.7 mm are tested with an error of less than 2%. The third study explores the detection of voids in a steel tank filled with lightweight grout. A joint analysis of surface waves and Lamb waves is used for void detection and the identification of debonding conditions in a laboratory scale model of a steel tank filled with grout. Different configurations of the MASW method are conducted using an instrumented hammer (large wavelengths, 10 cm < λ < 25 cm) and a 50 kHz piezoelectric transmitter (small wavelengths, 5 cm < λ < 9 cm) as sources. The attenuation coefficient computed from the Fourier spectra of the measured signals indicates that the presence of a void has an effect on the propagation of the wave. The comparison between experimental and theoretical dispersion curves show that mainly Lamb waves are generated during the testing of the steel tank; thus, detecting the debonding conditions between the steel plate and the grout. Lamb modes are used successfully for detecting the presence of a void beneath the steel wall. The laboratory measurements are effective in the detection of the void, showing amplitudes up to 50% higher, likely because the deformation of the wall is attenuated by the grout.

Material damage such as dislocations and microcracks are characteristic of early stages of fatigue. Accumulation of these nascent cracks leads to non-linear elastic response of the material. These non-linearities can be detected from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. An existing linear code was progressively modified to take into account a different constitutive law. Also the boundary conditions need to be reviewed to ensure free stress with the non-linear behavior. The propagation of the longitudinal wave is investigated in detail. Numerical accuracy is validated from comparison with a closed, for both linear and non-linear code. The reflection of the non-linear P-wave gives confirmation for the correct treatment of the boundary condition. Finally the capabilities of the Cellular Automata code are underlined for reflection of Lamb waves for various boundary conditions.

Structural health monitoring (SHM) is an active research area devoted to the assessment of the structural integrity of critical components of aerospace, civil and mechanical systems. Guided wave methods have been proposed for SHM of plate-like structures using permanently attached piezoelectric transducers, which generate and sense waves to evaluate the presence of damage. Effective interrogation of structural health is often facilitated by sensors and actuators with the ability to perform directional scanning. In this research, the novel class of Frequency Steerable Acoustic Transducers (FSATs) is proposed for directional generation/sensing of guided waves. The FSATs are characterized by a spatial arrangement of the piezoelectric material which leads to frequency-dependent directionality. The resulting FSATs can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. Because there is no need for individual control of transducer elements, hardware and power requirements are drastically reduced so that cost and hardware limitations of traditional phased arrays can be partially overcome. The FSATs can be also good candidates for remote sensing and actuation applications, due to their hardware simplicity and robustness. Validation of the proposed concepts first employs numerical methods. Next, the prototyping of the FSATs allows an experimental investigation confirming the analytical and numerical predictions. Imaging algorithm based on frequency warping is also proposed to enhance results representation.

Stoffwechsel und antioxidativer Status bei Merinofleischschafen im peripartalen Zeitraum Medizinische Tierklinik, Veterinärmedizinische Fakultät, Universität Leipzig Eingereicht im Juni 2010 (99 Seiten, 28 Abbildungen, 38 Tabellen, 357 Literaturangaben) Problem- und Zielstellung: Dem antioxidativen System wird im Rahmen von Stoffwech-seluntersuchungen bei Schafen nur wenig Bedeutung geschenkt, jedoch gewinnt es als Schutz- und Regulationssystem zunehmend an Bedeutung. Besonders die Trächtigkeit und die Frühlaktation bei Mutterschafen sowie die postnatale Entwicklung der Lämmer stellen enorme Anforderungen an die Energieversorgung und an das antioxidative System. Das Ziel dieser Arbeit ist, die Bewältigung dieser Anforderungen darzustellen und zu zei-gen, ob und wie stark Zwillingsträchtigkeiten ein Belastung für Mutterschafe darstellen, und ob Lämmer aus einer Zwillingsträchtigkeit möglicherweise benachteiligt sind. Tiere, Material und Methoden: Untersucht wurden insgesamt 23 trächtige Merinofleisch-schafe und zwölf Merinofleischschaflämmer. Bei 13 Muttertieren wurde sonografisch eine Einlingsträchtigkeit (M1) und bei zehn eine Zwillingsträchtigkeit (M2) festgestellt. Bei den Lämmern stammten sechs Tiere aus einer Einlingsgeburt (L1) und sechs aus Zwillingsge-burten (L2). Den Muttertieren wurden von der 5. Woche a.p. bis 1 Woche a.p. wöchentlich sowie 2 Wochen p.p., den Lämmern eine, vier und zwölf Wochen post natum Blutproben entnommen. Im Serum wurden die Konzentrationen von Betahydroxybutyrat (BHB), Glu-cose, Bilirubin, freien Fettsäuren (FFS), Gesamtprotein und Albumin, die Aktivitäten der Glutamatdehydrogenase (GLDH), sowie im Vollblut die Aktivitäten der Superoxiddismutase (SOD) und der Glutathionperoxidase (GPX) gemessen. Ergebnisse: Die SOD- und GPX-Aktivitäten stiegen gleichermaßen bei einlingsträchtigen und zwillingsträchtigen Muttertieren signifikant an. Die SOD-Aktivitäten stiegen bei M1 von 488,2 ± 28 vier Wochen a.p. auf 524,8 ± 96,1 U/g Hb eine Woche a.p. und bei M2 von 447,4 ± 65,1 fünf Wochen a.p. auf 619,4 ± 141,1 U/g Hb zwei Wochen p.p. an. Die GPX-Aktivitäten bei M1 stiegen von 782,1 ± 220,5 eine Woche a.p. auf 1037,62 ± 382,9 U/ml Hk zwei Wochen p.p.. M2 zeigten eine tendenziell niedrigere Aktivität, welche von 641,8 ± 118,4 auf 911,8 ± 168,5 U/ml Hk anstieg. Es bestanden signifikante Zusammenhänge der SOD mit FFS, BHB und Gesamtprotein sowie der GPX mit Bilirubin, FFS und GLDH. Für die SOD-Aktivität wurde ein Referenzbereich von 328,10 bis 837,25 U/g Hb und für die GPX-Aktivität von 473,38 bis 1259,05 U/ml Hk bei Muttertieren ermittelt. Ausgenommen die Glucosekonzentration eine Woche a.p. bestanden keine signifikanten Differenzen zwi-schen M1 und M2. Die BHB-Konzentrationen zeigten bis zur Lammung einen konstanten Verlauf und stiegen bei M1 eine Woche a.p. auf 0,59 ± 0,27 mmol/l sowie bei M1 und M2 zwei Wochen p.p. auf 0,76 ± 0,29 mmol/l (M1) bzw. 0,77 ± 0,25 mmol/l (M2) signifikant an. Gesicherte Korrelationen bestanden zu FFS, Gesamtprotein und Glucose. Die Gesamtprotein- und Albuminkonzentrationen verliefen über den gesamten Untersuchungszeitraum nahezu konstant. Die Albuminkonzentration sank bei M1 nach einem kontinuierlichen An-stieg von einer Woche a.p. (37,2 ± 2,9 g/l) zu zwei Wochen p.p. (35,3 ± 3,6 g/l) signifikant ab. Gesicherte Korrelationen bestanden zu Glucose, SOD, BHB, Bilirubin und FFS. Die Glucose- Konzentrationen stiegen bei M1 bis eine Woche a.p. auf 4,84 ± 1,17 mmol/l sig-nifikant an, korrelierten neben den Proteinen mit Bilirubin und fallen 2 Wochen p.p. wieder auf ihren Ausgangswert ab, der bei M2 konstant blieb. Die Bilirubinkonzentrationen verlie-fen konstant, die der FFS fielen nach einem Anstieg eine Woche a.p. (M1) signifikant ab. Die GLDH-Aktivitäten zeigten a.p. einen konstanten Verlauf und p.p. einen signifikanten Anstieg auf 20,61 ± 14,11 U/l bei M2. Zwischen L1 und L2 bestanden zu keinem Zeitpunkt signifikante Unterschiede. Die SOD zeigte abnehmende Aktivitäten mit zunehmendem Lebensalter, - bei L1 von 757,7 ± 94,4 eine Woche p.p. auf 597,8 ± 255,0 U/g Hb 4 Wochen p.p. und bei L2 von 487,17 ± 353,3 auf 464,0 ± 330,9 U/g Hb. Sie korrelierte gesichert mit Albumin und Glucose in der ersten Lebenswoche. Die GPX-Aktivitäten stiegen mit zunehmendem Lebensalter bei statistisch gesicherter Korrelation mit Glucose von 724,3 ± 199,8 auf 1011,5 ± 132,9 U/ml Hk bei L1 und von 693,3 ± 120,8 auf 1052,0 ± 146,9 U/ml Hk bei L2. Für Lämmer wurden als Refe-renzwerte 43,00 bis 932 U/g Hb für die SOD bzw. 406,00 bis 1321,00 U/ml Hk für die GPX berechnet. Die Albumin- und BHB-Konzentrationen stiegen zur vierten bzw. zwölften Le-benswoche an, die Glucose-, Bilirubin- und FFS-Konzentrationen im Serum sanken zur 12. Lebenswoche ab. Die Gesamtproteinkonzentration und die Aktivität der GLDH verlie-fen konstant. Es bestanden signifikante Korrelationen zwischen BHB und Gesamtprotein, FFS, GLDH sowie zwischen Gesamtprotein und Glucose, Albumin sowie FFS. Des Weite-ren bestanden gesicherte Korrelationen zwischen Bilirubin und FFS sowie FFS und GLDH. Fazit: Die Aktivitäten der antioxidativen Enzyme SOD und GPX sowie die Konzentrationen der klinisch-chemischen Parameter zeigen mit dem Anstieg der SOD-Aktivität von 447 auf 619 U/g Hb bei M2 einerseits die peripartalen Belastungen und andererseits mit dem An-stieg der GPX-Aktivität von 782 auf 1038 U/g Hk bei M1 die Kompensations- und Regel-mechanismen bei dieser Belastungssituation auf. Die Untersuchungen entsprechen dem Zustand einer ausgeglichen Energiebilanz und gesundheitlich stabilen Bedingungen. Ein Einfluss der Lämmerzahl auf das antioxidative System bzw. den Stoffwechsel kann weder bei Mutterschafen noch bei Lämmern statistisch signifikant belegt werden. / Metabolism and antioxidative status of merino sheep for meat production in the peripartum time period Large Animal Clinic for Internal Medicine, Faculty of Veterinary Medicine, University of Leipzig Submitted in June 2010 (100 pages, 28 figures, 38 tables, 357 references) Definition of the problem and objective: Until now, the research regarding the metabol-ism of sheep focussed very little on the importance of the antioxidative system, but the significance of its function as a protective and regulative system is increasing. Especially the pregnancy and the early lactation of the ewes as well as the postnatal development of the lambs places enormous demands upon the energy supply and the antioxidative sys-tem. The objective of this study is to show how these demands are met and to determine whether a twin-pregnancy represents an additional stress for the ewes, and whether lambs from a twin-pregnancy are possibly disadvantaged. Animals, materials and methods: 23 pregnant merino ewes and twelve merino lambs were analyzed. Sonographic tests showed that 13 ewes were pregnant with one lamb (M1), and ten showed a twin-pregnancy (M2). Six of the lambs were born as single lambs (L1), six as twins (L2). Blood samples were taken from the ewes every week from the fifth until the week before the birth, as well as two weeks after birth, the blood samples from the lambs were taken one, four and twelve weeks postpartum. The concentration in the serum of the following components was measured: betahydroxybutyrate (BHB), glucose, biliru-bine, free fatty acids (FFS), total protein and albumine, the activity of the glutamatedehy-drogenasis (GLDH), as well as the activity in whole- blood of superoxidedismutasis (SOD) and glutathionperoxidasis (GPX). Results: The SOD- and GPX-activities rose significantly at the same rate for mother sheep pregnant with one lamb or with twins. The SOD-activity rose for M1 from 488,2 +/- 28 four weeks prepartum to 524 +/- 96,1 U/g Hb one week prepartum, and for M2 from 447,4 +/- 65,1 five weeks prepartum to 619,4 +/- 141,1 U/g Hb two weeks prepartum. The GPX-activity for M1 rose from 782,1 +/- 220,5 one week prepartum to 1037,62 +/- 382,9 U/ml two weeks postpartum, while M2 showed a tendency towards lower activity, which rose from 641,8 +/- 118,4 to 911,8 +/- 168,5 U/ml Hk. There were significant correlations between the SOD and the FFS, the BHB and the total protein as well as the GPX with bili-rubine, FFS and GLDH. For the ewes, an SOD-activity reference range between 328,10 and 837,25 U/g Hb was determined, and a GPX-activity reference range between 473,38 and 1259,05 U/ml Hk. There were no significant differences between M1 and M2 except for the concentration of glucose. The BHB-concentration stayed constant up to birth and then rose significantly to 0,59 +/- 0,27 mmol/l for M1 one week postpartum and for both M1 and M2 to 0,76 +/- 0,29 mmol/l (M1) and 0,77 +/- 0,25 mmol/l (M2) two weeks postpartum. A reliable correlation could be determined with FFS, total protein and glucose. The total protein and the albu-mine concentration stayed almost constant during the whole analyzed time period. After a continuous increase between one week prepartum (37,2 +/- 2,9 g/l) and two weeks post-partum (35,3 +/- 3,6 g/l), the albumine concentration dropped considerably. Here, reliable correlations could be determined with glucose, SOD, BHB, bilirubine and FFS. For the group M1, the glucose concentrations rose significantly until one week prepartum to 4,84 +/- 1,17 mmol/l, correlated with both the proteins and bilirubine, then fell back to their initial level two weeks postpartum, while they did not change for M2. The concentrations of bili-rubine stayed constant, the FFS-concentrations fell significantly after an increase one week prepartum (M1). The GLDH-activities showed a constant trend prepartum, then rose significantly postpartum to 20,61 +/14,11 U/l for M2. There were no significant differences between L1 and L2 at any time. The SOD showed decreasing activity with increasing age, from 757,7 +/- 94,4 one week prepartum to 597,8 +/- 255,0 U/g Hb four weeks postpartum for L1 and from 487,17 +/- 353,3 to 464,0 +/- 330,9 U/g Hb for L2. A reliable correlation was determined with albumine and glucose in the first week after birth. The GPX-activities rose with increasing age with a statistically reliable correlation with glucose from 724,3 +/- 199,8 to 1011,5 +/- 132,9 U/ml Hk for L1 and from 693,3 +/- 120,0 to 1052,0 +/- 146,9 U/ml Hk for L2. The calculated reference val-ues for lambs were 43,00 to 932 U/g Hb for SOD and 406,00 to 1321,00 U/ml Hk for GPX. The concentrations of albumine and BHB rose towards the fourth and respectively the twelvth week of life, the levels of glucose, bilirubine and FFS dropped towards the 12th week. The total protein concentration and the GLDH-activities stayed constant. There were significant correlations between BHB and total protein, FFS, GLDH as well as between total protein and glucose, albumine and FFS. In addition, there were reliable correlations between bilirubine and FFS and FFS and GLDH. Conclusion: The activities of the antioxidative enzymes SOD and GPX as well as the concentrations of the clinical-chemical parameters show the prepartum stress on one side with the rise of the SOD-activity from 447 to 619 U/g for the group M2, and the compensa-tion and regulation mechanisms during this stress period on the other side with the in-crease of the GPX-activity from 782 to 1038 U/g Hk for the group M1. The results of the tests correspond to the status of a well-regulated energy balance and stable health condi-tions. An influence of the number of lambs on the antioxidative system or the metabolism for both lambs and ewes can not be shown with statistical significance.