Posted: 19:00:00, Thursday, Mar 22, 2007 Expiration: 19:00:00, Thursday, Mar 29, 2007
Source Rumen Microbiology and its Role in Ruminant Nutrition by James Russel.
Monensin (Brand name Rumensin)
- Antibiotic initially developed as a coccidiostat (antiprotozoan for chicken)
- It's a Ionophore, by definition these are hydrophobic molecules produced by Streptomyces species, that are able to dissolve in membranes and destroy ion gradients.
Effects on cattle:
- Feedlot cattle fed monensin consumed less feed and had 6% greater feed efficiency.
- Grazing animals gained weight 15% faster.
- Prevents bloating, mechanism not determined.
- Gram positive bacteria (generally more sensitive)
Effects on ruminal fermentation:
| Inhibition of H2 Producers
|| Inhibition of NH3 Producers
|| Inhibition of Lactate Producers
| ↑ Propionate:acetate
↑ Protein availability
- Methane production declines 30 to 50%.
- decreases acetate:propionate ratio (depending on diet as follows: forage fed cattle normal 4:1 monensin 2.5:1 grain fed cattle 1:1 normal (already a low ratio) monensin doesn't have a big effect)
Mechanisms of action:
The structure looks like a "donut" (see structure below)
Once bound to a metal ion or proton, the molecule can move accros the membrane, and shuttles into the cell Sodium and out of the cell Potassium ions.
Because the sodium gradient is larger than the potassium gradient, there is a net accumulation of protons and intracellular pH declines. The cell uses its membrane bound ATPase to re-establish the gradient, depleting the ATP the cell gets de-energized and stops growing.
Monensin Structure 3D image in www.accelrys.com
A review paper