Newest publications
Evaluation of fresh and preserved sheep faeces as an inoculum source in in vitro gas production assays
(2025) Rippstein, Lena; Rodehutscord, Markus
In order to meet the animals’ requirements of energy and nutrients, knowledge of the feed value of individual feed components is essential. In this context, information on ruminal degradability of feeds is crucial for formulating rations for ruminants. Information of this kind can be obtained using in vitro methods, such as the Hohenheim gas test (HGT). This method allows for the estimation of the organic matter digestibility and the energy value, as well as the protein value of ruminant feeds when applying the extended HGT (eHGT). In vitro methods provide a cost-efficient, rapid, and standardisable alternative to in situ and in vivo approaches, while contributing to reducing animal burden and the number of experimental animals. However, the HGT currently depends on using rumen fluid, which is commonly obtained from rumen-cannulated animals. Due to ethical concerns related to animal welfare and practical considerations, there is growing interest in replacing rumen-cannulated animals for the in vitro feed evaluation in the HGT and eHGT systems. However, the use of individual enzymes or enzyme mixtures for in vitro evaluation of feeds has not yet proven suitable for adequately representing the complex microbial activity of a rumen fluid inoculum (RI). In contrast, several findings in the literature indicate the potential of faeces as an alternative inoculum source to rumen fluid. However, to date, this approach has not been established in the routine analysis of ruminant feeds. The overarching aim of the present thesis was to systematically evaluate the suitability of sheep faeces as an alternative inoculum source to rumen fluid in the HGT. To this end, in vitro gas production (GP) was compared between faecal inoculum (FI) and RI. Additionally, the potential of using preserved faeces as an alternative inoculum source to fresh faeces, as well as the application of FI in the eHGT system, was evaluated. To compare faeces and rumen fluid as inoculum sources in the HGT and eHGT, RI was prepared according to the standard procedure using rumen fluid obtained from two rumen-cannulated lactating dairy cows and FI was prepared from rectally collected faeces of three adult wether sheep. The objective of Manuscript 1 was to examine whether FI and RI generally follow similar GP kinetics and to assess whether feed-specific variation could be observed. Furthermore, there was considerable interest in determining whether FI-GP and RI-GP are related to each other, as this could provide the basis for the future applicability of FI. A total of 90 currently relevant ruminant feeds from various categories and differing nutrient compositions were incubated in vitro with both FI and RI for 72 h, with multiple readings in the HGT. By using FI, lower GP kinetics were observed across all feed categories compared to RI. On average of all feeds, the potential GP was 9 mL/200 mg dry matter (DM) lower and the GP rate was 3.1%/h lower with FI than RI. Additionally, a lag phase of 1.51 h was estimated with FI, whereas no lag phase was observed for RI. The results indicate an overall lower fermentation activity of FI compared to RI. Despite these differences, the GP kinetic curves of the two inocula exhibited a very similar progression. Moreover, strong linear relationships were found between RI-GP at 24 h, the common incubation time of RI in the HGT, and FI-GP at both 24 h (Slope = 1.02, R² = 0.97) and 48 h (Slope = 1.1, R² = 0.97). Additionally, within the scope of this thesis, linear regression analyses were conducted based on a combined dataset from Manuscript 1 and previous studies. By using data from more than 400 different feeds in these analyses, the strong linear relationships between RI-GP at 24 h and FI-GP at 24 h (Slope = 0.98, R² = 0.93) as well as 48 h (Slope = 1.02, R² = 0.96) were confirmed. Dividing the dataset into the feed categories roughages and concentrates for the calculation of separate regression equations did not provide a clear advantage over using a single equation for all feeds. Despite the lower GP observed with FI, a consistent relationship was evident between the GP of both inocula across the different feeds, enabling a reliable estimation of RI-GP from FI-GP in the HGT. The use of preserved instead of fresh faeces would allow for a centralised housing of donor sheep, thereby reducing the number of animals required and improving standardisation. The aim of Manuscript 2 was to investigate the effect of differently preserved sheep faeces on the in vitro GP of nine different feeds and the microbiome in the HGT, intending to maintain a high level of microbial activity during incubations. Seven different freezing and freeze-drying treatments were applied. On average across all feeds, the potential GP of the frozen treatments (61 mL/200 mg DM) was comparable to that of the fresh faeces (62 mL/200 mg DM), whereas the freeze-dried treatments accounted for only 71-85% of the fresh faecal value. The results were confirmed by metaproteome analyses, as the microbiomes of the fresh and frozen treatments were significantly different from that of the freeze-dried treatments based on the relative abundance of the core proteins (p < 0.001). This demonstrated that stress factors associated with the freeze-drying process significantly impaired the microbiome, consequently affecting fermentation activity and GP. By contrast, the freezing process appeared more gentle on the microbiome, preserving a high microbial activity. Furthermore, strong relationships were found between RI-GP at 24 h and GP of the frozen treatments at 48 h of incubation (Slope = 1.27, R² = 0.96). Additionally, the effect of storage on freeze-dried and frozen treatments was investigated, revealing a considerable negative impact on GP and its relationship with RI-GP for both treatments. This limits the high potential for estimating RI-GP, which was particularly demonstrated with frozen faeces, and therefore requires further research. Manuscript 3 aimed to investigate the potential suitability of FI in the eHGT for estimating the protein value of ruminant feeds. The eHGT is used to estimate ruminally undegradable crude protein (RUP) and microbial crude protein. Ammonia-nitrogen (NH3-N) is a key parameter in this context, as it is released during microbial crude protein degradation and provides a nitrogen source for the microbes. FI and RI were therefore compared based on NH3-N and calculated microbially bound nitrogen (mN) following in vitro incubation of six different feeds for 8, 24, and 48 h. The NH3 N content was 17 and 23% lower with FI than with RI after 24 and 48 h, respectively. With RI, mN values decreased over the incubation time for most feeds, whereas with FI, mN initially increased before declining at later incubation times. This suggests that crude protein degradation and microbial binding of nitrogen occur more slowly and to a lesser extent with FI. However, both inocula demonstrated a comparable response to an additional energy source and showed strong linear relationships for NH3-N, particularly after 24 h (Slope = 1.39, R² = 0.98), indicating similar microbial mechanisms in faeces and rumen fluid. The RUP was also estimated for both inocula in this thesis, and the results showed an inconsistent ratio between FI and RI incubations across the six feeds. Similarly, an inconsistent ratio between the two inocula was observed for the mN data. Therefore, further studies involving a larger number of feeds, as well as the testing of mathematical approaches, are necessary to better evaluate the suitability of FI for estimating the protein value of ruminant feeds with the eHGT. In conclusion, the use of sheep faeces as an inoculum source for the in vitro analysis of ruminant feeds can be considered suitable for replacing rumen fluid and thus rumen-cannulated animals in the HGT. By reliably predicting the RI-GP from FI-GP, the predicted RI-GP can be used in the official and validated equations to estimate organic matter digestibility and metabolisable energy of ruminant feeds. The methodological approach applied in this thesis, including sheep feeding, faeces collection, and inoculum preparation, appeared appropriate in achieving a high and consistent microbial activity in the FI. Furthermore, a high potential was demonstrated for using preserved, particularly frozen, sheep faeces for application in the HGT, as well as the use of FI for estimating the protein value of feeds in the eHGT. However, further investigations are required for the two application fields to assess the suitability of FI comprehensively.
Design and development of an accessible open-source augmented reality learning authoring tool for applications in agroecological settings
(2024) Shidende, Deogratias; Treydte, Anna
Augmented Reality (AR) has emerged as a transformative educational technology, offering immersive, multisensory learning experiences that enhance engagement, conceptual understanding, and contextualization. In agroecology, where students must grasp complex ecological interactions and context-dependent knowledge, AR can bridge the gap between classroom instruction and field-based learning. However, the creation of AR content remains largely inaccessible to many educators in higher learning institutions (HLIs), particularly those without programming skills and individuals with disabilities such as the deaf and hard of hearing (DHH), and the blind and low vision (BLV). This dissertation addresses the central question: How can an accessible AR learning authoring tool enable non-technical educators and users with disabilities to create AR learning experiences for agroecology education in HLIs?
To address this question, the study employed a design-based research (DBR) methodology, integrating Agile Scrum for iterative, inclusive tool development. Seven research questions (RQ1–RQ7) guided the investigation. First, a document-based analysis (RQ1) compared open-source software licenses (OSLs) to determine their suitability for academic–industry collaboration. Permissive licenses (e.g., MIT, BSD) were found to offer more flexibility in code reuse and integration, thereby promoting long-term project sustainability, although they require supplementary legal mechanisms to ensure reciprocity.
Next, functional and non-functional software requirements (RQ2) were elicited through stakeholder workshops, interviews, surveys, and accessibility evaluations. These requirements informed the selection and redesign of MirageXR, an open-source AR platform. Key accessibility features were specified for DHH users, such as customizable captioning of audio augmentations, and for BLV users, such as voice navigation and spatial audio cues. These enhancements underscored the dual instructional and assistive roles of AR tools.
In response to RQ3, a modular, component-based software architecture was designed using the C4 model. This enabled seamless integration of external services (e.g., 3D object repositories, learning management systems, and automatic speech recognition) and ensured that features could be added or updated without disrupting system stability. This modularity was essential given the evolving nature of AR technologies.
The design and implementation phases (RQ4 & RQ5) employed participatory iterative prototyping with user feedback throughout the development process. Accessibility features were integrated into image, audio, and video augmentations, with functionalities such as caption editing, playback speed control, and 3D spatial positioning. These solutions directly addressed gaps in existing AR authoring tools, particularly for DHH and BLV users.
The sixth research question (RQ6) investigated usability and applicability through an AR creation workshop involving 24 agroecology educators. Findings revealed that although participants initially encountered difficulties, they gained proficiency over time. UMUX scores showed a correlation between AR experience and perceived usefulness. Participants highlighted AR's potential to visualize complex concepts and engage students in experiential learning. However, limitations in 3D content availability and customization highlighted the need for integrated 3D content creation and editing tools specifically tailored to agroecology.
To answer RQ7, the study conducted a systematic literature review of 60 studies to identify current accessibility evaluation methods in AR. Most evaluations employed task-based scenarios, utilizing metrics such as time on task, error rate, and user satisfaction. The study's own evaluation validated that DHH users could independently author AR content using the developed tool. In contrast, BLV users could navigate the authoring functionalities but were unable to fully author AR content, indicating that further design improvements and assistive functionalities are required for full inclusion.
Methodologically, this study contributes a novel integration of DBR and Agile Scrum for inclusive educational technology design. This hybrid framework facilitated rapid prototyping, iterative refinement, and participatory co-design, and is recommended for broader application in accessibility-focused educational innovation. Future research should document and validate this methodological approach across additional contexts and user groups.
The study makes the following contributions: (1) provision of an open-source, extensible AR authoring interfaces and codebase for public use; (2) improved AR accessibility for AR for DHH and BLV users; (3) development of modular architectural and algorithmic solutions to enable multimodal accessibility; (4) empirical validation of AR’s pedagogical value in agroecology education; and (5) identification of optimal open-source licensing models for collaborative educational software development.
In sum, the findings demonstrate that an accessible, open-source AR authoring tool can empower diverse educators, including those with disabilities, to create inclusive and contextually relevant learning experiences. The research affirms the importance of universal design, participatory development, and modularity in educational technology design and concludes with strategic recommendations: integrating AI-assisted 3D content generation, expanding accessibility to additional user groups, and establishing communities of practice to support sustainable AR content development in agroecology.
Effects of herbal feed additives and processing methods on the concentration of skatole in the adipose tissue of pigs
(2024) Marro, Philipp; Stefanski, Volker
Die betäubungslose Kastration männlicher Ferkel ist seit 2021 verboten; Alternativen wie die Ebermast bergen jedoch das Risiko von Ebergeruch, der hauptsächlich durch Androstenon und Skatol verursacht wird. Da ein ausreichender Schutz der Verbraucher vor geruchsbelastetem Fleisch bislang nicht gewährleistet ist, werden sowohl fütterungsbasierte Maßnahmen zur Reduktion der Skatolbildung als auch verarbeitungstechnische Ansätze diskutiert. Ziel der Arbeit war es daher, den Einfluss verschiedener Pflanzenextrakte und ätherischer Öle aus Oregano, Schisandra chinensis und Knoblauch auf die Bildung und den Abbau von Skatol zu untersuchen und gleichzeitig die Wirksamkeit der Fleischverarbeitung zur Reduktion von Skatol und Androstenon zu bewerten.
Die Untersuchungen zum Skatolstoffwechsel bei kastrierten männlichen Schweinen zeigten, dass die Supplementierung der Zusätze in die Aktivität des Cytochrom-P450-Enzymkomplexes (CYP2E1 und CYP2A) eingreifen kann. Knoblauchöl senkte die Aktivität von CYP2A und führte zu erhöhten Skatolkonzentrationen in Plasma und Fettgewebe. Oregano und Schisandra chinensis hatten dagegen keinen Einfluss auf die enzymatische Aktivität oder die Skatolkonzentrationen. Die Analyse des Darminhalts entlang des Dickdarms zeigte ebenfalls keine reduzierende Wirkung der Zusätze; zudem gab es keine Unterschiede in der Skatolproduktion zwischen Caecum, Colon und Rektum. Eine Korrelationsanalyse machte deutlich, dass bei Zugabe von Knoblauch und Schisandra chinensis positive Zusammenhänge zwischen den Skatolkonzentrationen in Plasma, Fett und Darminhalt bestehen. Insgesamt konnten die eingesetzten Zusätze unter den verwendeten Bedingungen – einschließlich Konzentration, Darreichungsform und Anwendungsdauer – die Skatolkonzentration nicht senken, während Knoblauch sie sogar erhöhte.
Die Untersuchung der Fleischverarbeitung anhand von Salami, Wiener Würstchen und Leberwurst ergab, dass Androstenon durch Hitzeeinwirkung reduziert werden kann, während Skatol insbesondere durch Räucherung verringert wurde. Eine Kombination beider Verfahren erscheint somit als geeignetes Mittel, um stark geruchsbelastetes Fleisch weiterzuverarbeiten und verbrauchertaugliche Produkte herzustellen.
Insgesamt zeigt die Arbeit, dass die getesteten ätherischen Öle und Pflanzenextrakte unter den untersuchten Bedingungen nicht zur Senkung der Skatolkonzentration beitragen. Gleichzeitig wird deutlich, dass spezifische Verarbeitungsschritte ein wirkungsvolles Instrument darstellen, um die Geruchsbelastung von Fleisch mit erhöhtem Androstenon- und Skatolgehalt zu reduzieren.
Emotions and entrepreneurial finance: analysis of venture capitalists’ and business angels’ digital footprints on Twitter
(2024) Kaiser, Manuel; Kuckertz, Andreas; Kaiser, Manuel; Entrepreneurship Research Group, University of Hohenheim, Wollgrasweg 49, 70599, Stuttgart, Germany; Kuckertz, Andreas; Entrepreneurship Research Group, University of Hohenheim, Wollgrasweg 49, 70599, Stuttgart, Germany
Emotions are a central concept in previous entrepreneurship research, but this is mainly related to entrepreneurs and their entrepreneurial journey. However, venture capitalists (VCs) and business angels (BAs), two critical investors in the entrepreneurial finance literature, are essential actors in the entrepreneurial process. Still, little is known about investor emotions in this context. Therefore, in this study, we ask how venture capitalists differ from business angels in terms of their expressed emotions. To this end, we use an increasingly familiar research approach by examining the digital footprints of these investors on Twitter. For this purpose, we identify 822 investors from Crunchbase and analyze their 994,969 Tweets with Linguistic Inquiry and Word Count (LIWC) as a text analysis tool. Our results show that venture capitalists display more positive emotions on Twitter than angel investors, meaning that we find an association between VCs and emotional tone. Furthermore, in our post-hoc analysis, we explore further explanations for the differences between VC and BA. In doing so, we show differences in their expressed cognitive processes as well as in their communicated drivers. In both concepts, we find positive associations with the investor type of VC. To conclude this paper, we develop implications for practice and further research based on the results.
Complex European invasion history of Anoplophora glabripennis (Motschulsky): new insights in its population genomic differentiation using genotype-by-sequencing
(2024) Haeussermann, Iris; Hasselmann, Martin; Haeussermann, Iris; Institute of Animal Science, Department of Livestock Population Genomics, Centre for Biodiversity and Integrative Taxonomy (KomBioTa), University of Hohenheim, Stuttgart, Germany; Hasselmann, Martin; Institute of Animal Science, Department of Livestock Population Genomics, Centre for Biodiversity and Integrative Taxonomy (KomBioTa), University of Hohenheim, Stuttgart, Germany
Anthropogenic activities like trade facilitate increasing rates of biological invasions. Asian long-horned beetle (ALB), which is naturally distributed in eastern Asia (China, Korean peninsula), was introduced via wood packing materials (WPM) used in trade to North America (1996) and Europe (2001). We used 7810 single nucleotide polymorphisms (SNPs) derived by a genotype-by-sequencing (GBS) approach to decipher the introduction patterns into Europe. This is applied for the first time on European ALB outbreaks from Germany, Switzerland, and Italy, both from still active and already eradicated infestations. The genome-wide SNPs detected signs of small and highly structured populations within Europe, showing clear founder effects. The very high population differentiation is presumably derived from multiple independent introductions to Europe, which are spatially restricted in mating. By admixture and phylogenetic analyses, some cases of secondary dispersal were observed. Furthermore, some populations suggest admixture, which might have been originated by either multiple introductions from different sources into the new sites or recurrent introductions from an admixed source population. Our results confirmed a complex invasion history of the ALB into Europe and the usability of GBS obtained SNPs in invasion science even without source populations.