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Dilution effects on magnesium efflux from the rumen

Allen, M.S. and Russell, J.B. and Mayland, H.F. (1988) Dilution effects on magnesium efflux from the rumen. In: Proc. Tetany Times VIII Biannual Workshop. Magnesium Metabolism in Soils, Plants and Animals. USA-NJ-New Brunswick, 1988/07/19. 1 pp.

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Factors affecting magnesium absorption from the rumen are integrally
involved in grass tetany because most of the absorbed Mg passes through
the rumen wall. Recent work has shown that ruminal Mg absorption occurs
by a sodium-linked active transport following saturation kinetics. The dilution
effects on Mg absorption were evaluated by a dynamic simulation of Mg
flow in the rumen. As several factors in the rumen influence Mg availability,
a simple rumen submodel was developed to predict rumen parameters (fiber
content, microbial mass, liquid dilution rate, particulate passage rate) for
different conditions. Cation-exchange capacity of fiber and the microbial
mass as well as insoluble Mg complex formation reduce the available Mg
pool for absorption in the model. Preliminary results for 500 kg cattle grazing
crested wheatgrass (DMI = 1.2 % BW / day), indicate that efficiency of
magnesium absorption from the rumen was greatly affected by liquid dilution
rate. Without considering insoluble Mg precipitate formation, the efficiency
of Mg absorption from the rumen ranged from .41 to .31 as the rumen liquid
fractional passage rate varied from .08/h to .14/h. Factors affecting the
rumen liquid dilution rate include rumen water holding capacity, saliva
secretion, rumen osmolarity, and water intake from drinking and eating.
Kinetic factors may be responsible for the poor efficiency of absorption of
Mg under conditions when rumen liquid dilution rates are high.

Item Type: Conference or Workshop Item (Paper)
NWISRL Publication Number: 0662
Subjects: Animal > Animal health
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:56
Last Modified: 05 Jan 2017 19:18
Item ID: 922