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Abstract

Our objective was to evaluate the influence of substrate dispersion method and particle size on in vitro digestibility, gas production kinetics and composition, and fermentation characteristics of different feed types. Alfalfa hay, tall fescue hay, ground corn, soybean meal, and a total mixed ration (TMR) were used as substrates. Treatments were designed according to a 2 × 2 × 5 factorial arrangement: two substrate dispersion methods (loose substrate and in filter bags), two particle sizes (1 mm and 2 mm), and five feeds. Filter bags decreased (P ≤ 0.001) digestibility and gas production compared with loose samples. Filter bags decreased digestibility and total gas production to a greater extent for forages, whereas the effects on concentrate feeds were less pronounced. Using filter bags decreased (P ≤ 0.015) both methane production and methane concentration in headspace gas across all feeds. Substrates incubated in filter bags showed a lower molar proportion of acetate and a greater molar proportion of propionate than loose substrates (P< 0.001). In general, energy-rich feeds incubated using filter bags had a decreased (P ≤ 0.036) acetate-to-propionate ratio, while substrate dispersion method did not influence (P ≥ 0.16) the VFA profile of protein-rich feeds. Incubating substrates in filter bags alters in vitro digestibility, gas production, and fermentation characteristics regardless of particle size. However, the magnitude of responses is greater for forage-based feeds than concentrate feeds.

Document Type

Article

Publication Date

2026

Notes/Citation Information

© 2026 Sousa, Matos, Trotta, Detmann and Harmon. 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) and the copyright owner(s) 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.

Digital Object Identifier (DOI)

https://doi.org/10.3389/fanim.2026.1749974

Funding Information

The author(s) declared that financial support was received for this work and/or its publication. This work is funded by Hatch Capacity Grant Project no. KY007088 from the USDA National Institute of Food and Agriculture and Project 201807121511 from USDA/ARS and the University of Kentucky Agricultural Experiment Station.

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