Brown Midrib Corn
March 6, 1997 4(3):16-18
Joe Lauer and Jim Coors
Corn Agronomist and Corn Breeder
Currently there is much interest in the dairy industry about brown midrib corn.
Brown midrib corn was first discovered in dent corn at St. Paul, MN in 1924. It
was thought to occur as a natural mutation of regular dent corn. Since its initial
discovery a total of four brown midrib mutants have been identified:
- bm1 (Jorgenson, 1931)
- bm2 (Burnham and Brink, 1932)
- bm3 (Emerson et al., 1935)
- bm4 (Burnham, 1947)
Brown midrib corn plants exhibit a reddish-brown pigmentation of the leaf midrib
at V4 to V6. The pigmentation is also seen in rind and pith. Coloring eventually
disappears on leaves, but remains in the stalk. The brown midrib phenomenon is also
found in sorghum, sudangrass, and pearl millet.
About 40 years after the initial discovery, bmr mutations were found to have
a drastic effect on lignin (Lechtenberg et al., 1972) and that digestibility of
corn silage was improved in ruminants. Below are the initial studies involved with
- sheep (Muller et al., 1972)
- goats (Gallais et al., 1980)
- heifer cattle (Colenbrander et al., 1972, 1973, 1975)
- beef cattle (Keith, 1981)
- dairy cows (Frenchick et al., 1976)
A total of 18 agronomic and dairy cattle feeding trials comparing brown midrib corn
and regular dent corn were summarized (Fig. 1). Usually either yield or quality
results were published, rarely both. In these studies, brown midrib corn produced
on average 6% less yield than regular dent corn. Fiber as measured by ADF and NDF
was 3 and 2% lower for brown midrib than regular dent corn. Using MILK91 (Undersander
et al., 1993), milk per ton and milk per acre were calculated and brown midrib corn
increased milk per ton 4%, but decreased milk per acre 2%.
In the U.S. results of feeding bmr corn are either inconclusive or trended
slightly in favor. A significant increase in milk production was observed only once
(Keith et al., 1979). Increased body weight was noted every time bmr was
fed. Energy intake was not limiting in these studies and it seems that extra nutrients
digested in bmr corn are partitioned into meat or fat body tissues rather
than milk. Feeding results from England (Weller and Phipps, 1986) and France (Hoden
et al., 1985) indicate increased milk production. Some things to think about as
you consider using brown midrib corn as a corn silage in your dairy operation:
Advantages include:sadvantages include:
- Lower yields: Whole plant silage and Grain
- Susceptibility to lodging
- Poor early season vigor
- Delayed flowering
- Slower early season growth rates
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