ORIGINAL RESEARCH article
Front. Anim. Sci.
Sec. Animal Nutrition
Volume 6 - 2025 | doi: 10.3389/fanim.2025.1620969
Optimization of RUSITEC Model Adaptations for In vitro Simulation of Subacute Ruminal Acidosis and Evaluation of Saccharomyces cerevisiae Supplementation on Microbial Fermentation and Stability
Provisionally accepted
- 1Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre, Quebec, Canada., Quebec, Canada
- 2dsm-firmenich, Animal Nutrition and Health R&D-Center, Tulln, Austria., Tulln, Austria
- 3Clinical Center for Ruminant and Camelid Medicine, University of Veterinary Medicine, Vienna, Austria, Vienna, Austria
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There is a growing need for alternative research models to reduce or replace animal use in feed and feed additive testing. In vitro model development could provide value added data in the assessment of feed additives for microbial modulation in cattle where animal variation in intake can impact results. This study aimed to refine and evaluate the in vitro model of subacute ruminal acidosis (SARA) and assess how variations in buffer and feed additive supplementation could influence microbial fermentation and community composition. We hypothesized that using a different reactor agitation style would provide more consistent results for fermentation and community composition when using a SARA model. As well we hypothesized that supplementation with Saccharomyces cerevisiae (AY) could mitigate the negative effects of SARA by stabilizing rumen pH and supporting microbial balance. Using the rumen simulation technique (RUSITEC) with a SARA model, buffer dilution and feed additive supplementation were compared for their influence on microbial fermentation and community composition. Results showed that buffer dilution, combined with dietary changes, effectively induced SARA in vitro, with a significant impact on ruminal pH and fermentation parameters. Acetate production and pH were lower in reactors supplemented with Saccharomyces cerevisiae (AY), especially under low buffering conditions, suggesting AY's potential to mitigate ruminal dysbiosis. Microbial protein and protozoa abundance also changed in response to dietary and buffer adjustments. This study supports the use of in vitro models for more controlled, reproducible testing of feed additives, with potential applications in improving nutritional interventions and rumen microbial stability. Future work should explore RUSITEC models for metabolomics and bacterial function studies.
Keywords: in vitro, RUSITEC, Acidosis, feed additive, yeast, diversity, Fermentation
Received: 30 Apr 2025; Accepted: 29 Jul 2025.
Copyright: © 2025 Petri, Antlinger, Khol, Gruber and Kesselring. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Jutta C Kesselring, dsm-firmenich, Animal Nutrition and Health R&D-Center, Tulln, Austria., Tulln, Austria
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