The Real Scoop on Brown Midrib Corn Silage
Written by Ev Thomas and Dan Wiersma*
Two seed companies market brown midrib (BMR) corn hybrids for use as silage in dairy rations. Breeders use both bm1 and bm3 genes to produce the various BMR hybrids. For the purpose of this column, we’ll make (what we consider quite reasonable) the assumption that there’s more difference in yield, starch content, and fiber digestibility between silage made from BMR and non-BMR corn hybrids than there is between BMR hybrids bred with different brown midrib genes.
Why assumptions and not facts?
Because there’s not enough data from university silage hybrid trials comparing the yield and quality of BMR hybrids with different brown midrib genes to make a definitive determination. BMR hybrids are frequently not included in university hybrid testing programs. In other variety testing programs (including trials at Penn State), the BMR hybrids are analyzed separately from non-BMR hybrids using wet chemistry rather than NIR. This can result in an “apples to oranges” comparison.
The First Take Away
What we can say about BMR corn silage: It puts milk in the tank!
Compared to normal hybrids, BMR hybrids produce forage that has reliably lower lignin content. BMR forage is typically about 10 percentage points higher in fiber digestibility than non-BMR corn hybrids since lignin is completely indigestible. Higher fiber digestibility often results in higher feed intakes and greater milk production by dairy cows.
There have been many trials comparing silage from BMR to normal and leafy corn hybrid types. Almost all have found higher milk production with BMR forages. Milk production responses vary depending on how much BMR is in the ration as well as the production level of the cows in the trial.
Higher-producing cows typically have a greater response to BMR corn silage. This is logical since adequate dry matter intake and high forage digestibility becomes a limiting factor as milk production goes up. Milk production responses to BMR silage tend to be greatest in high corn silage rations where BMR silage is at least 10 to 12 pounds of dry matter intake. Feeding a low rate of BMR corn silage may not result in any milk production response . . . BMR requires commitment!
The Matter of Lodging
One of the claimed disadvantages of BMR corn is poor standability. It’s true that BMR hybrids have less lignin and those plants are more susceptible to lodging. However, when managed properly — including not pushing plant populations too far and timely harvest — lodging is seldom a problem.
In the many years that Cornell University ran its New York statewide corn silage hybrid testing program, Bill Cox never reported significant lodging in the trials, including the BMR hybrids. In fact, standability data isn’t included in any of the state university corn silage hybrid trials we reviewed for non-BMR or BMR hybrids..
Much of what we know about BMR standability is from field experience. Occasional lodging problems are often associated with severe weather. In other cases, BMR hybrids may lean over but they seldom lodge to such an extent that harvest is difficult. Plant BMR corn at the seed company-recommended population, maintain good soil fertility, and harvest at the proper stage of maturity to avoid significant lodging issues.
HIGHER YIELDING COWS TYPICALLY HAVE A GREATER RESPONSE to BMR corn silage. This becomes logical since adequate dry matter intake and high forage digestibility becomes a limiting factor as milk production goes up. That means it is logical to store BMR in a separate silo, bag or drive-over pile and feed to high-producing groups of cows.
The Elephant in the Room
Speaking of “issues,” there’s the yield drag that seed company representatives selling against BMR hybrids seem to be so fond of mentioning. It is true; BMR hybrids can yield less than non-BMR silage hybrids. Again, university data is rather sparse, but it appears that when harvested for silage, BMR corn yields about 10 percent less than the best non-BMR corn silage hybrids planted. (It should be noted that BMR is intended only for silage harvest, not for grain.)
In addition, BMR corn silage hybrids have traditionally been more susceptible to drought stress as compared to non-BMR hybrids. Plant your BMR hybrids on fields with good moisture-holding capability.
Some farmers will never plant BMR because of the yield drag. Another way of looking at it is to consider BMR corn to be an entirely different crop from non-BMR corn. BMR corn is just different: the seed costs more, recommended plant population is often less, the crop looks different growing in the field, and some crop consultants even claim that it tastes different.
The combination of higher seed cost and lower yield means that every pound of BMR corn silage costs more to produce. To get the greatest benefit from BMR’s superior digestibility, ensile the BMR forage in a separate silo, bag or drive-over pile and feed to high-producing groups of cows.
We don’t get upset when our alfalfa, oats, or triticale doesn’t yield as much as our normal corn. Why should it bother us when a crop with such unique properties — both in the field and in the feedbunk — doesn’t yield quite as much as “normal” corn hybrids?
*Ev Thomas is retired from the William H. Miner Agricultural Research Institute and president of Oak Point Agronomics Ltd. Dan Wiersma is the alfalfa business manager with DuPont Pioneer.
Used by permission from the May 10, 2016, issue of Hoard’s Dairyman. Copyright 2016 by W.D. Hoard & Sons Company, Fort Atkinson, Wisconsin.