Managing Corn Silage Variability

Posted: July 2, 2012

Corn silage quality changes more than the weather at the Penn State Dairy Farm.
Penn State Dairy Cows

Penn State Dairy Cows

The challenge with 2013 corn silage is not only the low fiber digestibility and starch, but the variability in starch content moving from structure to structure. This has meant more frequent forage testing along with ration adjustments to accommodate the variability. For the first time we utilized BMR corn silage in May to off-set the less than stellar analysis on the conventional silage.

Corn silage quality has been a moving target. The analysis of the next upright at the end of April was similar to the bag being fed to the herd, which was low in starch. Maintaining cow performance would be a challenge especially with warmer temperatures coming. Our strategy the last few years has been to save BMR corn silage for July to help keep cows milking during the months with the highest heat and humidity. We were fortunate last year to get a bunk and 1.5 bags of BMR. After talking with the assistant managers and evaluating our options, we decided to open the bag with half BMR and conventional. Our plan was to open the bag at the BMR end and feed 50/50 BMR and the other structure of conventional corn silage. The bag was marked so we would know when transitioning into the conventional end. At that time we would open the full bag of BMR and continue feeding a 50/50 mix. If things worked out according to plan, cows would get the 50/50 mix through the end of June and then switch to the BMR bunk. The bunk typically lasts close to 3 months, which would still allow us to feed a highly digestible forage during the worst part of the summer.

Table 1 shows the difference between the BMR and conventional corn silage fed in May. Both have similar fiber content with the fiber digestibility being very high in the BMR, which should be expected. The starch level in the BMR was low along with a low starch digestibility compared to the conventional.

Table 1. Comparison of BMR vs. conventional corn silage.

BMR Conventional
NDF, % DM 41.9 40.4
NDFD, 30 hr, % NDF 68.9 51.1
Starch, % DM 26.4 33.2
Starch digestibility, 7 hr, % starch 69.8 81.9

The BMR corn silage was lower in dry matter compared to what had previously been fed. Tracking our components I noticed when starting the BMR milk fat and especially milk protein started to slip. Beginning on the 20th, the herd was switched from 7.2 pounds of ground corn as-fed to 3.6 pounds each of coarse and ground corn. As soon as that change was made the response in components was immediate. Averaging the components pre/post change, milk fat percent was 3.67%/3.75% and milk protein percent 3.06%/3.12%, respectively. Milk production remained the same.

There was another noticeable change in May and that was the feed cost per cow. Based on market prices of forages and home raised grains (corn and soybeans) feed prices are still relatively high. Additionally dry matter intakes increased when BMR corn silage was started. The combination of these two factors substantially increased the feed cost in May compared to the previous months. The good news is that even with the higher feed cost, cow performance was maintained and a good IOFC was achieved. Feed cost as a percent of milk income was a bit higher at 34% compared to the previous months of 29-30%. For the month of May the herd averaged 85.2 pounds with a 3.69% milk fat, 3.08% milk protein, 146,000 SCC and 7.7 mg/dl MUN.

IOFC Results
Month and Year Gross Milk Price/cwt Milk income/cow Feed cost/cow IOFC Average milk lbs Low Benchmark High benchmark
M-13 $20.60 $17.78 $7.23 $10.55 86.3 $7.11 $10.67
J-13 $20.49 $17.91 $7.16 $10.75 87.4 $7.16 $10.74
J-13 $20.54 $16.43 $6.56 $9.87 80 $6.57 $9.86
A-13 $20.47 $16.38 $6.99 $9.39 80 $6.55 $9.83
S-13 $21.06 $17.56 $7.09 $10.47 83.4 $7.03 $10.54
O-13 $21.55 $18.53 $6.57 $11.96 86 $7.41 $11.12
N-13 $21.97 $18.24 $6.66 $11.58 83 $7.29 $10.94
D-13 $22.83 $19.63 $6.51 $13.12 86 $7.85 $11.78
J-14 $24.53 $21.10 $6.17 $14.93 86 $8.44 $12.66
F-14 $26.09 $22.05 $6.90 $15.15 84.5 $8.82 $13.23
M-14 $27.01 $23.31 $6.81 $16.50 86.3 $9.32 $13.99
A-14 $27.03 $23.35 $6.75 $16.60 86.4 $9.34 $14.01
M-14 $26.30 $22.41 $7.70 $14.71 85.2 $8.96 $13.44

IOFC Graph

May 2014

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Managing Corn Silage Variability

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Contact Information

Virginia A. Ishler
  • Extension Dairy Specialist
Phone: 814-863-3912