Loading...
Effects of isoleucine and valine supplementation on the biosynthesis of branched-chain fatty acids by ruminal microorganisms in continuous culture fermenters
Matthews, Lily
Matthews, Lily
Citations
Altmetric:
License
License
DOI
Abstract
Branched-chain fatty acids (BCFAs) are a unique class of saturated fatty acids with methyl branches, found primarily in ruminant-derived foods such as milk and meat, and are thought to offer potential health benefits to humans. While BCFA biosynthesis from branched-chain amino acids (BCAAs) is well established in certain bacterial species, it remains poorly characterized in the rumen environment. Accordingly, the overarching goal of this thesis was to investigate how supplementation with two BCAAs, isoleucine and valine, influences the microbial synthesis of their structurally related BCFAs: odd-chain anteiso-BCFAs and even-chain iso-BCFAs, respectively.First, to better support continuous culture fermenter (CCF) studies, a previously described filter design was modified to improve protozoal retention and maintain community structure. A novel reusable 3D-printed filter system was developed and validated over a 10-day period, in which models fitted with either a nylon bag or a polyurethane sponge were compared. The sponge filter maintained a protozoal composition more similar to the rumen inoculum, with entodiniomorphid protozoa comprising 85% of the total population compared to only 10% with the nylon bag and proved structurally stable and reusable. Subsequently, using this improved filter system, two 4 x 4 Latin square experiments were conducted, each with four 10-day periods and increasing doses of either isoleucine (0.65 –2.60 g/day) or valine (1.03–4.12 g/day). Fermenter contents and overflow effluent were analyzed to assess the fatty acid profile in bacterial and protozoal membranes, microbial community structure, fermentation parameters, and digestibility. Isoleucine supplementation resulted in a quadratic increase in total odd-chain anteiso-BCFAs and anteiso-15:0 in bacterial membranes. In contrast, only anteiso-15:0 showed a quadratic increase in protozoal membranes. Synthesis in both microbial membranes peaked at 1.95 g/d. Valine supplementation led to a linear increase in total even-chain iso-BCFAs, iso-14:0, and iso-16:0 in bacterial membranes, while in protozoal membranes only iso-14:0 increased linearly. Peak levels of BCFAs in both microbial membranes occurred at 4.12 g/d. Microbial community structures within CCFs were largely unaffected by BCAA supplementation, and no changes were observed in fermentation parameters or digestibility. Together, this work refines CCF methodology and advances the understanding of ruminal BCFA synthesis, establishing an experimental framework for dietary strategies to enhance BCFA content in ruminant products. Future research should validate these findings in vivo and explore interactions with other dietary components, informing precision feeding approaches to improve the nutritional quality and potential health benefits of dairy and meat products.
Description
Date
2025-01-01