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Cut the corn High-quality forage allows less corn in diets

15:32PM Jun 16, 2008
Photo courtesy of Deere & Co.
Feeding higher levels of highly-digestible corn silage can reduce the need for corn grain in rations.

When corn was $1.80/bu., you could feed it like there was no tomorrow. Except tomorrow came.

With corn prices now reaching the stratosphere, focusing efforts on highly digestible forages—be they grass, alfalfa or corn silage—will pay big dividends in both rumen health and milk production.

"These high corn prices give us an  opportunity to reduce starch from corn in the diet without negative consequences," says Randy Shaver, a University of Wisconsin Extension dairy nutritionist.

"With low, neutral detergent fiber (NDF) hay crops and highly-digestible corn silage, we can feed a higher forage ration and therefore really feed a lot less corn."

And save big dollars. Shaver assumes a blended concentrate price of 15¢/lb. of dry matter (DM) for corn, soybean meal and minerals/vitamins. If you can feed highly digestible, low NDF forages, concentrate amounts can be as low as 20 lb. DM/cow/day (at 50 lb./cow/day total DM intake) and concentrate costs can be as low as $3/cow/day.
But if you're forced to feed high NDF, low digestibility, forage rations, concentrate requirements can jump an additional 12 lb. DM/cow/day, or an extra $1.80/cow/day in feed costs. "You can see a pretty significant feed cost increases with low quality forage," says Shaver. 

The key, of course, to getting those savings is to harvest forages at the right, early maturities and then get them ensiled right for optimal fermentation and preservation.

Some of that digestibility work begins with variety and hybrid selection. Selecting corn hybrids, for example, means more than simply selecting for grain yield—also look at NDF
digestibility ratings and total silage tonnage. 
Some dairy producers have also turned to the higher fiber digestibility of brown mid-ribbed (BMR) corn. Companies who sell BMR say yield drag is much less an issue now than when it was first introduced. But others say it still can be subject to agronomic stress. So consider agronomics and yield in your hybrid selection, says Shaver.

Reducing starch. A number of researchers, including Shaver, have looked at the rations of high-producing herds (more than 30,000 lb./cow) and have found starch levels from 25% to 30% in their diets. "We do see this level of starch in high-producing herds and in research trials," he says. "But that may have been a function of corn grain being cheap in the past. This level of starch feeding is common, but I don't think it's necessary. 

"It does look like we can reduce that to 21% starch," he says. You can accomplish that by a number of strategies:

  • Use high-fiber, low-protein byproducts, such as soyhulls, to partially replace corn grains.
  • Use high-fiber, moderate-protein byproducts such as distillers grains to partially replace corn grain and protein supplement. "Even though distillers has run up in price along with corn and soybean meal, it still is priced below its break-even value on a nutrient basis," Shaver says.
  • Use a higher proportion of corn silage in the ration, paying particular attention to hybrid selection, harvest maturity and moisture, chop length and processing, and preservation.
  • Feed high-starch corn silage.
  • Supplement with sugars, such as molasses, sucrose, bakery or whey-based products if economical. Optimal sugar content of milking cow rations is 5% to 6%, with most base diets only containing 2% to 3% (DM basis). So limit supplemental sugar to 1 ½ lb. up to 2 lb./cow/day, which can replace up to 3 lb. of corn/cow/day.
  • Feed monensin. Feeding monensin, which improves feed efficiency, provides an energy equivalency worth about 2 lb. of corn/cow/day.

In addition, make sure that the starch in the corn you are feeding is highly digestible. The starch in high moisture corn in more digestible than the starch in dry corn, for example. 

Ground corn is more digestible than rolled; steam-flaked is better then dry rolled. Early maturity corn silage is better than late, and rolled or processed corn is better than unprocessed. 
Even if you are harvesting corn silage at the recommended 30% to 35% dry matter, Shaver still recommends processing corn silage. At that moisture, processing breaks up the cobs which results in a more consistent product, it packs better in the bunker and sorts less in the feed bunk.
And as moisture drops, processing becomes even more important to break apart corn kernels. By 40% dry matter or greater, there can be a 10% to 15% unit difference in starch digestibility between processed and unprocessed corn silage.
The same is true for corn grain. Dry rolled corn, with a particle size of 1725 microns, has a starch digestibility of about 75%. Grind corn, and particle size drops by two thirds and starch digestibility jumps to nearly 90%. 
Grinding high moisture corn, if it contains 27% to 30% moisture, yields only a slight starch digestibility advantage over rolling.

Finally, work with both your nutritionist and your agronomic team to develop your optimal feeding program. If you want to reduce the amount of corn you're feeding and take advantage of lower-cost corn replacements, your forage program is key. 
You need to grow that forage right, harvest at optimal maturity and moisture, and then get it preserved correctly. All those little things, done well, can add up to big savings in a time of historically-high corn prices, says Shaver.

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