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Modeling the distribution of ciliate protozoa in the reticulo-rumen using linear programming
S E Hook1, J Dijkstra, A-D G Wright
1Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of Guelph, Guelph, Canada. shook@uoguelph.ca
Journal of Dairy Science
|December 24, 2011
Summary
Rumen protozoa numbers are maintained by attachment to feed particles and the rumen wall, not just free-living populations. A new model shows 63-90% of protozoa are attached, suggesting fluid sampling underestimates total populations.
Area of Science:
- Rumen microbiology
- Mathematical modeling
- Animal nutrition
Background:
- Rumen ciliate protozoa flow is lower than expected based on total density.
- Protozoa numbers are maintained via selective retention with feed particles and the rumen wall.
- Existing mathematical models lack comprehensive representation of both free-living and attached protozoa phases.
Purpose of the Study:
- To develop an updated mathematical model for rumen protozoa.
- To accurately represent protozoa distribution, sequestration, and generation times.
- To quantify protozoa populations in both liquid and attached phases.
Main Methods:
- Development of a linear programming model for rumen protozoa in a steady state.
- Distinguishing protozoa in the liquid phase from those attached to particulate matter or the rumen wall.
- Incorporating growth, passage, death, and transfer rates between protozoa pools.
Main Results:
- The majority of rumen protozoa (63-90%) reside in the attached phase.
- A higher proportion of attached protozoa was observed in animals fed a hay diet compared to a starch diet.
- The model indicates that attached protozoa are a significant component of the total rumen protozoal community.
Conclusions:
- Rumen protozoa populations are predominantly attached to feed particles or the rumen wall.
- Experimental protocols sampling only rumen fluid may significantly underestimate total protozoal populations.
- Further research on ciliate protozoa distribution is needed to refine rumen microbial models.
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