One of the largest breakthroughs in corn silage quality has been the identification of the Brown MidRib (BMR) gene in corn and the development of hybrids that carry the gene. BMR hybrids generally have better fiber digestibility and lower levels of UNDF (undigestible fiber) than their conventional counterparts. This can allow dairy farmers to feed more forage in their diets and potentially get higher milk production. While the benefits of BMR corn are well documented I have been seeing a shift away from BMR corn the last few years.
Ask these questions to see if BMR is a good fit for your farm:
1. How much do you want to feed? A dairy cow has a minimum and maximum amount of UNDF240 that it can utilize. Too little can impact animal health and rumination. Too much can limit DMI and production. BMR corn has about 2% less uNDF240 (as a percent of dry matter) than conventional corns. If you are planning of feeding 80%+ of your forage as corn silage, BMR may benefit you because it will help keep the UNDF in a workable range.
2. Will you be feeding much alfalfa in the diet? While most rations are 6-7% UNDF240, average quality alfalfa may be 15%+ UNDF240. This can make it very hard to keep the overall ration low enough in UNDF. BMR can help with that and pairs nicely with alfalfa in a ration.
3. Do you have above average soil fertility and adequate moisture? While BMR corn may average 10-15% less yield than conventional corn, it is not as consistent. That means on good ground with adequate moisture, the yield drag may be negligible, but when BMR fails it generally does so spectacularly. It is just not a great agronomic fit on farms that are drought prone or have more marginal soils.
4. Do you have a large land base? The challenge with heavy BMR corn diets is that it not only yields less, but intakes also usually go up. High forage diets are wonderful if we have the forage, but if those inventories are tight, they can really be a challenge to make things work. The other issue is that BMR corn does best on a tight rotation with minimal corn-on-corn. If the whole farm is planted in corn, it can make crop rotation nearly impossible.
5. Can you wait to feed it? While Brevant’s Unified and the Kingfisher BMRs are floury, the majority of BMR corn has flinty starch and should ferment 3-6 months before feeding. Because BMR tends to have a little lower starch levels than convention corn, it is important to get the most out of the starch that it has.
While BMR has benefited many farms, it is not a magic bullet or even a requirement to gain high milk production or profitability. On my client farms that don’t use BMR corn, we focus on bringing digestible fiber into the diet with other forages like grasses and small grains. These can fill the digestible NDF requirement of the ration while keeping UNDF levels down. Grasses and small grains also give us crops to utilize manure and provide a healthy crop rotation.
