Dr. John Goeser
Questions continue coming in about BMR corn silage despite the hybrids being on the market and in the field for the past decade. You need to make seed corn decisions, but what’s the best corn silage?
The market has changed with BM-3 and BM-4 mutants on the market. “Brown midrib” is actually caused by a single gene mutation. The mutation can actually be inserted into any hybrid out there. However licensing restricts which hybrids hit the market. There are several BM mutations; the current mutations on the market are the 3 and 4 type. Regardless of type, the mutation stops the plant from thoroughly lignifying; making the fiber much more digestible, but also leaves a weaker stalk and lighter yield. The yield drag varies, but the BM corn silage entries published by the University of Wisconsin and Michigan State University hybrid trials lagged behind conventional hybrids by approximately 10 to 15% over the past several years (data not shown but is available upon request). So with this yield drag, is BM the right choice? I think so, at least in some capacity, as long as we understand what we’re working with.
As a grad student working in the UW Corn Silage Breeding program under Prof. James Coors, I experimented with various BM mutants. These plants were awesomely different and are hands down more digestible; easily capable of more milk if starch levels are relatively similar to conventional. I am a believer.
Through the lab, using our TTNDFD (Combs, 2012) tool which estimates how much fiber cows can actually digest, we’re seeing some overlap between BM and conventional hybrids. Clearly, however, commercial BMs are still a cut above for fiber digestibility (Figure 1). Each 1% increase in fiber digestibility (or TDN) yields about ½ lb milk (Oba and Allen (1999) and Schalla et al. (2012)) and we’re seeing 4.5% units higher NDFD for BMRs this year despite the abnormally high NDFDs we’re seeing for conventional corn silages. The one word of caution I’ll throw out is to make sure we still have adequate starch and overall energy levels. Higher fiber digestibility will never make up 5 or 10 % less DM in starch.
Figure 1: Total tract NDF Digestibility estimates for late 2012 customer submitted samples labeled as conventional or BM corn silages
Outside of BM hybrids, Conventional hybrids are making strides in fiber and starch digestibility. The corn germplasm (gene pool) is more diverse than any other plant out there, meaning there are big differences in hybrids. Seed companies have figured this out over the past decade and are giving us better and better hybrids. I have worked with several nutritionists and forage growers over the past several years and we’ve recognized the differences in conventional hybrids – gaining digestibility and milk with the right seed choices.
Since there is not an unbiased authority for seed corn, the best way to choose hybrids is to combine information sources (I call this cross referencing). I like to use University hybrid trials, seed company representatives and information and then any hybrid data from the farm we’re consulting for. Then we can sort out the top performing hybrids with confidence.
There’s one more option out here too: blending conventional and BM hybrids in the field. For example, 4 rows conventional and 4 rows BM throughout the field. This approach can result in intermediate yield and digestibility (University of Delaware work, Prof Kung) and might be a reasonable way to start getting experience with BM hybrids.
References are available upon request.