Managing Starch Digestibility Changes in Corn Silage

Careful planning keeps milk production high when the Penn State Dairy transitions to new corn silage.
Managing Starch Digestibility Changes in Corn Silage - Articles

Updated: August 8, 2017

Managing Starch Digestibility Changes in Corn Silage

Last year ended on a positive note in regards to animal performance. Research projects were finished and 2013 corn silage was started. Based on the silage analysis a new feeding strategy was required. Many dairy operations across Pennsylvania experienced reduced production when feeding corn silage harvested in 2013. My quandary was how to keep the Penn State herd from experiencing the same production loss.

A bag of 2013 corn silage was started in the middle of the month. It was the last corn harvested. It had the distinction of being one of the lowest quality samples I have observed compared to what other dairy producers had shared with me. On a dry matter basis it tested 44.4% neutral detergent fiber (NDF) with a 30 hour NDF digestibility of 50.7% (%NDF). The starch was 27% with a 7-hour starch digestibility of 70.4 (% starch). Compared to how our corn silage typically tests this had to rank as the worst analyses to date.

Table 1 lists the ration changes throughout December and the production response by the herd. Since the corn silage was high in fiber, low in starch and low in digestibility, I needed to focus on keeping adequate energy in the ration and to keep the ration as digestible as possible. For that reason I eliminated the hay and cottonseed hulls from the diet.

Table 1. Ration changes during transition from 2012 to 2013 corn silage.
Ingredient (DM Basis, lbs)Dec
1-16
Dec
17-23
Dec
24-31
Roasted soybeans3.73.163.1
Mineral + Optigen ®2.152.152
Grass hay2.61.30
Canola meal3.653.13.3
Candy meal3.64.54.5
Fine ground corn5.46.578.1
Cottonseed hulls1.500
Corn silage - 201226.214.30
Corn silage - 201301324.1
Alfalfa haylage9912
Liquid sugar2.5233
Percent forage in ration6562.560
Average milk production (lbs/cow/day)85.28786
Average milk fat, %3.533.573.7
Average milk protein, %3.133.163.15
Ration starch, %262522
Ration protein, %1514.514.5
Metabolizable protein deficiency (lbs.)-0.19-0.24-0.28

The other challenge was how to balance the ration for both protein and carbohydrates when dealing with a very low quality forage. My focus has always been on optimizing microbial protein and providing a diverse carbohydrate profile. Instead of manipulating the corn grain I focused on the sugar content of the diet. I increased the amounts of the candy meal and liquid sugar. I examined the impact of these diets on the metabolizable protein content in the ration using the 2001 NRC model. My diets were deficient by 0.28 pounds with the ration protein at 14.5% on a dry matter basis. Cows have been averaging 86 pounds consistently since starting the ration with 2013 corn silage. Fat test increased to 3.70% and protein is continuing to climb.

For the month of December the herd averaged 86 pounds with a 3.59% milk fat, 3.13% milk protein, 136,000 SCC and 7.5 mg/dl MUN.

IOFC Results

Month and YearGross Milk Price/cwtMilk income/cowFeed cost/cowIOFCAverage milk lbsLow BenchmarkHigh benchmark
D-12$22.17$18.62$6.65$11.9784$7.45$11.17
J-13$21.19$18.44$7.03$11.4187$7.37$11.06
F-13$20.64$18.58$7.58$11.0090$7.43$11.15
M-13$20.79$17.26$6.99$10.2783$6.90$10.35
A-13$20.57$17.28$7.23$10.0584$6.91$10.76
M-13$20.60$17.78$7.23$10.5586.3$7.11$10.67
J-13$20.49$17.91$7.16$10.7587.4$7.16$10.74
J-13$20.54$16.43$6.56$9.8780$6.57$9.86
A-13$20.47$16.38$6.99$9.3980$6.55$9.83
S-13$21.06$17.56$7.09$10.4783.4$7.03$10.54
O-13$21.55$18.53$6.57$11.9686$7.41$11.12
N-13$21.97$18.24$6.66$11.5883$7.29$10.94
D-13$22.83$19.63$6.51$13.1286$7.85$11.78

IOFC Graph

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