University of Illinois Extension

Illini DairyNet Papers

BMR — Questions and Concerns
Michael F. Hutjens
07/08/1998

A "hot topic" at World Dairy Expo was field observations and questions about BMR. Brown midrib corn (BMR) is the new corn silage on the block. Michigan State researchers reported that BMR is lower in lignin content (about half of normal corn silage), 6 to 8 percentage units higher in total plant digestibility, 5 pounds higher feed intake, and 5.5 pounds more milk per cow per day. Higher plant digestibility and dry matter intake are advantages when feeding high producing cows. Farmers questioned high seed prices last winter ($240 per bag) and lower corn silage yields (from 8 to 20 percent). The following comments and questions were raised.

  1. The BMR corn silage is wet. Dairy producers have delayed chopping 1 to 2 weeks waiting for it to dry down. In northern regions, dairy managers are anxious as cold weather and poor harvest conditions could develop.
  2. The height of BMR corn silage varied from 2 foot shorter to taller than control corn silage. Ears were shorter, the same sized, fully pollinated, or partially pollinated.
  3. The windy day (Sept 29th) caused damage to all corn silage, with the BMR taking a bigger hit or no difference.

To answer some of these questions, Illinois dairy extension workers had seven Illinois dairy farmers volunteer last winter to collect data on their farms comparing BMR to their best corn silage hybrids (control corn silage). Dry matter yield, plant population, standability, digestibility (to be determined at Michigan State University), and milk production response will be collected. Preliminary data is summarized in Table 1 (all farms had not finished at this time).

For farmer with BMR corn silage, the following strategies can be considered.

  1. New York DHI has announced that they can determine the in vitro dry matter ($19 per sample) and NDF + dry matter ($23 per sample) digestibility for forages. Samples are incubated in rumen fluid for 30 hours to simulate rumen retention time. Because the plant is more digestible, traditional ADF and NDF values will not reflect higher energy values. A digestibility test of your BMR corn silage would be solid investment along with your traditional corn silage variety for comparison.
  2. Assign an additional 3 to 5 energy units (TDN or net energy-lactation) for higher digestibility. If your normal corn silage has 0.70 Mcal of net energy-lactation per pound of dry matter, plug in .74 or .75 for BMR in your computer. This shift will lower the amount of grain energy and increase forage levels.
  3. Because the fiber is higher in digestibility, monitor total ration ADF and NDF levels. Higher levels of fiber may be needed to maintain optimal rumen function and pH.

BMR is a new forage! Adjust for digestibility and nutrient differences. Watch your cows, they will be "talking" to you (manure changes, dry matter intake, body condition score, signs of acidosis, and milk yield and component shifts). We will know more in the next six months.

RESULTS

Table 1 lists the results obtained from the seven cooperator farms. Generally, BMR corn silage was lower in ADF and dry matter content and higher in crude protein content compared to high yield corn silage control corn silage brands. Dry matter yields were lower with BMR corn silage and were shorter compared to the control. A milk increase (estimated to be 2 to 3 pounds more milk per cow) will be needed to cover higher seed costs and reduced yield. Appreciation is expressed to Illinois dairy farmers who cooperated with this field demonstration: Brian Woker, Ed Schumacher, Mark Erdman, Gerald Poppe, Keith Landis, Rodney Fuchs, and Doug Scheider.

Table 1. Preliminary Illinois dairy farm results comparing BMR and control high yielding corn silage (values separated with a diagonal indicates two different samples on the farm).

Herd A BMR Silage Control Silage
Dry matter (%) 36.9 42.8
Crude protein (%) 8.97 6.93
ADF (%) 26.5 28.6
Plant height (inch) 80 90
Ear length (inch) 10 11
Plants per acre 24,412 24,045
Yield (ton DM/acre) 5.4 6.5
Herd B BMR Silage Control Silage
Dry matter (%) 27.1/28.6 29.6/36.4
Crude protein (%) 9.7/10.2 10.5/9.5
ADF(%) 21.8/26.3 27.6/21.9
Plant height (inch) 96/88 98/106
Ear length (inch) 7 8
Plants per acre 27,000 25,000
Yield (ton DM/acre) 6.1 7.2
Herd C BMR Silage Control Silage
Dry matter (%) 31.2 27.8/31.5
Crude protein (%) 12.2 12.5
ADF (%) 23.7 24.6
Yield (ton DM/acre) 5.2 4.6/6.1
Herd D BMR Silage Control Silage
Dry matter (%) 31.7 32.9/38.2
Crude protein (%) 9.7 9.5/9.4
ADF (%) 14.5 17.7/11.5
Yield (ton DM/acre) 8.3 9.3/8.7
Herd E BMR Silage Control Silage
Dry matter (%) 33.0 34.8
Crude protein (%) 9.0 8.7
ADF (%) 27.3 29.0
Plant Height (in) 89 102
Planting Population 31,500 31,500
Harvest Population 27,200 27,650
Yield (ton DM/acre) 6.0 6.9
Herd F BMR Silage Control Silage
Dry matter (%) 41.2 40.1
Crude Protein (%) 9.3 9.0
ADF (%) 24.2 22.6
Plant Height 91 96
Planting Population 31,500 31,500
Harvest Population 28,900 24,400
Yield (ton DM/acre) 6.3 7.2
Herd G BMR Silage Control Silage
Dry Matter (%) 38.2 43.6
Crude Protein (%) 9.9 8.7
ADF (%) 20.9 21.7
Plant Height 81 97
Planting Population 27,000 27,000
Harvest Population 22,000 24,625
Yield (ton DM/acre) 7.6 8.4