A new laboratory test measures the amount of starch that rumen fluid digests in 12 hours.

The test can be used to analyze samples of corn silage, high-moisture corn and corn grain, explains Dave Taysom, director of Dairyland Labs, Arcadia, WI. Dairyland developed the test along with Donald Sapienza of Sapienza Analytica, a testing lab at Slater, IA.

“Starch is 45% of the total energy contribution or feeding value in corn silage,” says Taysom. “This test looks at how digestible that starch contribution is, providing additional information to help fine-tune rations.”

To date, the starch digestibility of several corn silage samples analyzed with the new test has ranged from 70% to 94%.

“The higher the percentage of starch digestibility in that feed, the more energy or utilization the animal can get from it,” he says.

Here's how the test works: When a silage sample arrives at the lab, it's ground until 70% of the particles are 6-8 mm long. Next, the sample is placed in a specially designed Dacron bag and incubated in a flask of rumen fluid for 12 hours.

“Twelve hours was selected as the time period to use because other research tells us that's the probable amount of time starch is digested once it enters the rumen,” points out Taysom.

The rumen fluid, which is collected one hour after feeding, is pooled from four cows. “That's an important step because the fluid might vary somewhat from one cow to another.”

Each sample is tested four times and the values are averaged.

Taysom recommends that producers or nutritionists send in a sample right after a silo is opened.

“Once they get that initial value, they may want to test it again three to six weeks later to see if it's changed,” he says. “We speculate that the digestibility will increase the longer it's in the silo. That's because the fermentation acids continue to work on the kernels, softening them up and making them more digestible.”

The test costs $55/sample and takes up to seven days. Taysom says Dairyland-Sapienza also has a test that measures the digestibility of starch that passes undigested from the rumen to the intestines. He calls the two tests the total-tract starch digestibility package.

For more information, contact Dairyland Laboratories, Inc., 217 E. Main, Arcadia, WI 54612. Phone: 608-323-2123.