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Published on: July 31, 2019
In vitro Inoculation of Fresh or Frozen Rumen Fluid Distinguishes Contrasting Microbial Communities and Fermentation
Zhi Yuan Ma1,2, Ju Wang Zhou1, Si Yu Yi1
1Chinese Academy of Sciences (CAS) Key Laboratory for Agro-Ecological Processes in Subtropical Region, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Processes, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China.
Frozen inocula (INO) can be used in in vitro rumen batch cultures, as their effects on fermentation and microbial communities are independent of substrate type. This allows for reliable studies on rumen fermentation and microbial diversity.
Area of Science:
- Rumen microbiology
- Animal nutrition
- In vitro fermentation technology
Background:
- In vitro rumen batch culture simulates rumen fermentation using rumen microorganisms.
- Frozen inocula (INO) offer advantages for storage and transport but their impact on fermentation relative to substrate type is unclear.
Purpose of the Study:
- To investigate if rumen fluid treatments (fresh vs. frozen INO) interact with different concentrate-to-forage ratios (C/F) in in vitro rumen batch cultures.
- To assess the effects of INO type and C/F on rumen fermentation and microbial community composition.
Main Methods:
- A complete block design with fractional arrangement was employed.
- Treatments included fresh or frozen INO and two C/F ratios (1:4 and 1:1).
- Evaluated dry matter (DM) degradation, volatile fatty acids (VFA) concentration, VFA profile, and bacterial community diversity.
Main Results:
- Increasing C/F ratio typically increased DM degradation and total VFA, decreased the acetate to propionate ratio, and reduced bacterial diversity.
- Frozen INO decreased DM degradation and altered VFA profiles compared to fresh INO.
- Crucially, no significant interaction between INO type and C/F ratio was observed for substrate degradation, VFA profile, or bacterial community (P ≥ 0.20).
Conclusions:
- The effects of concentrate-to-forage ratios on rumen fermentation and bacterial diversity are not influenced by the type of inocula (fresh or frozen).
- Frozen inocula are a viable alternative to fresh inocula for in vitro studies, enabling reliable assessment of substrate effects, including starch content.
