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The Economics of Replacement Decisions in Swiss Dairy Farming

Doctoral Thesis

Schlebusch, Simon (2026)

Deciding when and which dairy cows to replace is one of the most economically impactful decisions in herd management, yet also one of the most complex. In Switzerland, 20% to 40% of cows are replaced annually, often after only three to four lactations—well below the economically optimal lifespan of five to six lactations. This gap suggests room for improvement in culling strategies, particularly under increasing pressure to balance farm profitability with animal welfare, environmental sustainability, and genetic progress. The goal of this dissertation is to better understand and improve the economics of replacement decisions in Swiss dairy farming through a combination of modeling, simulation, and empirical analysis. The core of this work is the development of a flexible decision-support model using a Markov Chain framework. The model estimates cow survival probabilities and monthly profit margins, producing an economic indicator—referred to as the “cow value”—which reflects the expected economic contribution to overall farm profitability of each individual cow. By integrating cow-specific parameters such as milk yield, breed, pregnancy status, and replacement costs, the model allows for a tailored assessment of optimal replacement decisions. This cow-level approach offers a novel, data-driven alternative to herd-wide average indicators and creates a foundation for precision herd management. The thesis consists of seven chapters, including three peer-reviewed manuscript chapters. The first chapter is the general introduction to the topic; the first study then (Chapter 2) presents the methodology of the cow value model and demonstrates its functionality using real data from Swiss farms. The model enables the identification of underperforming cows and supports individualized culling decisions based on expected lifetime profitability. The second study (Chapter 3) explores how market conditions—particularly milk, heifer, and carcass prices—affect optimal replacement strategies across 181 Swiss farms. The results highlight the economic sensitivity of replacement rates to external price shifts and show how factors like breed and herd-level productivity influence the optimal timing of culling. The third study (Chapter 4) compares farmers’ actual replacement decisions with those recommended by the model, using data from 29 dairy farms. While most decisions align broadly with economic logic, the analysis also reveals excessive culling in lower parities, often due to fertility or health problems, resulting in measurable economic losses. The general discussion (Chapter 5) synthesizes these findings, suggesting that Swiss farmers generally make rational decisions under the constraints they face, but that targeted improvements—particularly in fertility and health management—could extend cow longevity and improve farm profitability. The cow value model, with its modular and customizable design, provides a foundation for a practical decision-support tool and can be extended in future work to incorporate environmental costs, policy incentives, or animal welfare metrics.

Comparative characterization of mitochondrial components across size-defined extracellular vesicle populations derived from HaCaT keratinocytes

Data Collection

Brigger, Finn; Kitanovic, Ana; Meurant, Sébastien; et al. (2026)

Human-Based Placenta-Embryo Microfluidic Co-Culture Platform for Developmental Toxicity Assessment of Drugs and Nanoparticles

Doctoral Thesis

Murdeu, Manon (2026)

There is a general lack of human-based developmental and reproductive toxicology (DART) studies regarding effects and mechanisms of drugs, nanoparticles (NPs) and environmental pollutants on the developing human embryo. Furthermore, conventional animal testing in DART does not fully recapitulate the complex physiology of human development, leading to species-specific differences in placentation, xenobiotic metabolism and developmental timing limiting the predictive values of the toxicological outcomes. This limitation arises from ethical and safety constraints surrounding the inclusion of pregnant women in clinical trials, together with the continuously expanding number of chemicals and nanomaterials ex-ceeding the capacity of conventional animal-based testing. As a result, this data gap creates significant safety concerns and evidences the need for advanced models that accurately mimic the maternal-embryonic axis. Current in vitro approaches to study embryotoxicity mostly focus on the direct effects of xenobiotics on the developing embryo, often overlook-ing the maternal-foetal interaction and the important role of placental factors that can indi-rectly influence embryo-foetal development. Advanced culture systems, particularly organ-on-chip technologies, provide a powerful plat-form for the integration of multiple human tissues within a single, controlled microphysio-logical environment. By enabling the co-culturing of different cell types in spatially orga-nized and perfused compartments, these systems allow for recapitulation of key aspects of tissue architecture and function that are difficult to achieve in conventional static in vitro models. Importantly, organ-on-chip platforms facilitate not only the independent study of individual tissues, but also the investigation of their mutual interactions under physiologi-cally relevant conditions, including the ability to monitor inter-tissue communication mak-ing them particularly well suited for modelling complex biological systems, such as the ma-ternal-foetal axis, and for studying their crosstalk including drug response, transport and developmental toxicity. To allow for evaluation of both, direct and indirect effects, this thesis is aimed at establishing a human-based co-culture on chip combining a placental barrier model and an embryoid body (EB) within a single microfluidic platform. It includes the following major sections. 1. A study describing the establishment of a human-based model of the maternal-em-bryonic interface. The microfluidic device included maternal and embryonic com-partments in which a primary derived placental barrier and a human induced pluripo-tent stem cell (hiPSC)-derived EB were cultured in close vicinity. 2. A proof-of-concept study with a known embryotoxic compound. Valproic acid (VPA), a known teratogen compound, was used to assess the effects on morphology, viability and disruption of ectodermal differentiation of EBs in presence or absence of the placental barrier, showing the important role of the placenta in the modulation of developmental toxicity. 3. A section describing the safety assessment of therapeutic nanoparticles. Prussian Blue (PB)-Mn engineered nanozymes for the treatment of inflammation during preg-nancy were evaluated in the newly developed microfluidic system. Placental trans-location of NPs was assessed in presence or absence of inflammatory conditions, and two different exposure scenarios were examined, demonstrating the suitability of the model for nanomedicine safety evaluation. Overall, the developed platform was shown to accurately recapitulate placental physiology and morphology as well as human relevant physiological processes, such as hormone secre-tion, polarization and human-relevant foetal transfer rates of drugs and NPs. The EB model, capable to differentiate into all three germ layers, showed early ectodermal features that are important for the assessment of neurodevelopmental adverse outcomes. The suitability of the platform for studying different compounds places it within the framework of new ap-proach methodologies (NAMs) to gain early-stage data for drug and NP hazard assessment. The platform will contribute to the progress in the field of nanomedicine and to the protection of sensitive populations like pregnant women and developing foetuses, while reducing the need for extensive animal testing.

Probing flavour deconstruction via primordial gravitational waves

Journal Article

Fabri N.; Isidori G.; Racco D. (2026)

European Physical Journal Plus

We study the production of primordial gravitational waves (GWs) from first-order phase transitions (FOPTs) in extensions of the Standard Model based on Flavour Deconstruction (FD). The link fields inherent to FD generically form a rich scalar sector, with sizeable couplings at the TeV scale, providing natural conditions for strong FOPTs and correspondingly large GW emission. We identify the key parameters controlling the GW spectrum and enabling its detection at future GW observatories. In particular, we find that while FD scenarios can yield detectable signals, the resulting spectra typically peak at higher frequencies than the millihertz range. As a consequence, a positive observation at LISA is possible but not guaranteed, while the signal falls in the range of mid-band proposals, making FD models an intriguing target for upcoming GW searches.

Multisensor Edge Angle Detection for Performance Analysis in Ski Jumping

Journal Article

Simeonov I.; Schulthess L.; Mueller H.; et al. (2026)

IEEE Sensors Journal

In ski jumping, performance during the gliding phase depends on achieving an aerodynamic posture that maximizes the lift-to-drag ratio. In the V-style technique, the ski edge angle is a key determinant. Reducing the edge angle flattens the skis, increases their effective surface area, and improves aerodynamic lift, ultimately contributing to longer flight distances. Ski edge angles are biomechanically constrained by the limited range of ankle inversion. Increasing ankle inversion initially reduces the ski edge angles, thereby improving aerodynamic efficiency. However, inversion beyond the controllable biomechanical range may result in unstable edge configurations and asymmetric pressure distributions, thereby degrading aerodynamic efficiency and flight stability. Current sensing solutions widely quantify these angles using multisystem approaches that combine sensor signals through geometric relations. Such configurations require instrumentation on both the boot and the ski, altering mass distribution, affecting balance during flight, and increasing system complexity. To overcome these limitations, this work presents a wearable sensing system that measures both boot inclination and ski edge angle without modifying the ski surface. Two ultrasonic time of flight (ToF) sensors and an in-shoe inertial measurement unit (IMU) are integrated into a single boot-mounted unit. Edge angles are estimated by combining ultrasonic distance measurements with Inertial Measurement Unit (IMU) data through geometric reconstruction of the boot-ski configuration. Laboratory experiments demonstrate an angle resolution of 0.4500°, a mean absolute error (MAE) of 0.2640°, and a coefficient of determination exceeding 99% when compared with reference measurements, indicating strong linear agreement between the two modalities. The system achieves an end-to-end latency of 30.31 ms, enabling real-time feedback suitable for athlete training while consuming 1.28 mW of power. With a total weight of only 18.6 g, the proposed system enables unobtrusive measurement of ski edge angle and boot orientation.