‘Cutter’ Forages Can Fit Well Into Heifer Rations

By Ron Johnson Dairy Editor
Thursday, October 23, 2008 7:44 AM CDT

Don’t waste your best forages on dairy heifers. They just don’t need all that energy.

Instead, blend into their ration lower-quality hay if you’re feeding things like corn silage or distiller’s grains, advised Wayne Coblentz, during a presentation at the recent World Dairy Expo. Coblentz is a research dairy scientist and agronomist with the U.S. Dairy Forage Research Center and is based at Marshfield, Wis.

He offered a few thoughts on forage quality, noting that poorer forage doesn’t have to only consist of stemmy grass hay. Alfalfa’s quality drops when it’s cut at a later stage of maturity, so delaying cutting is one way to make forage that’s fine for heifers.

Likewise, the weather can play a large role in forage quality. Heat or wind, or both, while hay is drying will drop the quality.

“Forage quality is highly dependent on climate, forage type, harvest management and many other factors,” the agronomist reminded.

Research at Marshfield has looked into how fast dairy cattle digest forages of varying maturities. Young alfalfa, in its vegetative stage of growth, was found to be nearly 78 percent digested after 12 hours in a heifer’s rumen. After 48 hours, it was 84 percent digested.

Alfalfa harvested later, in the bud stage, was 65 percent digested after 12 hours, and nearly 71 percent digested after 48 hours, Coblentz reported. When alfalfa was a bit older, in the mid-bloom stage, digestion slowed even more, to 59 percent digested after 12 hours, and to 66 percent after 48 hours.

Even orchardgrass, sometimes not thought of as making high-quality forage, can be quite digestible if it’s cut early enough or is grazed young enough. For orchardgrass, the research found that when it’s in its second node of growth n quite young and rapidly growing n the grass was 71 percent digested after 12 hours, and was 85 percent digested after 48 hours.

As with alfalfa, the older the orchardgrass got, the slower it was digested. Harvested at full head, orchargrass was 54 percent digested after 12 hours, and was 72 percent digested after 48 hours.

One main reason alfalfa and grasses become less digestible the older they get is that they contain more lignin. And older grasses have more stem in proportion to their leaves, compared to younger grasses.

‘Right’ forage

There is no one “right” forage for all types of cattle, Coblentz said. Dairy heifers need a different kind of forage that cows that are milking heavily at the beginnings of their lactations.

“…Appropriate forage quality is highly dependent on what you intend to feed… A 1,200-pound beef cow wandering aimlessly in the Ozarks (needs an) energy density (in) her diet of about 47.1 percent total digestible nutrients,” Coblentz said.

That’s a “very low” amount of required energy if that beef cow is not pregnant and is not nursing a calf, he added. If that’s the case, she does not need top-shelf forage.

“Better, or high-quality (forage) is not always desirable,” the agronomist emphasized.

‘Cutter’ forage

Lower-quality forage can be especially useful as a “cutter,” according to Coblentz. That is, feed containing a higher amount of energy can be blended with forage containing a lesser amount of energy. In effect, the total ration energy is “cut” by adding the poorer forage.

“Many commercial dairy heifer growers would like to maximize the use of corn silage and by-products of the ethanol industry in the diets of replacement heifers,” Coblentz said. “This has created the need for ‘cutter’ forages that ideally exhibit high dry matter yield, high fiber, low energy, high protein and low potassium (content).”

The fiber content of such a “cutter” forage should be at least 70 percent, he explained. Its energy content should be 45 to 50 percent of its TDN. Its protein should amount to about 15 percent. And it should contain about 1.5 percent potassium.

“As you might imagine, finding a best like that is pretty difficult,” Coblentz remarked.

Whichever kind of “cutter” forage is used, it can especially have a place in the rations of dairy heifers weighing 900 to 1,200 pounds. A ration for 900-pound heifers could be made of 43 percent corn silage and 43 percent alfalfa silage, with the rest made up of a “cutter” forage.

For heifers weighing 1,200 pounds, 39 percent of the ration’s TDN could come from corn silage, with another 39 percent from alfalfa haylage. Then, the remaining 22 percent of the TDN might be provided by a poorer forage.

Oat straw or barley straw might be a suitable “cutter” forage, Coblentz said. Or it might be a tropical corn, or a warm-season perennial grass, depending on a farm’s location.

If those are not available nearby, getting a “cutter” forage might be as simple as letting a stand of alfalfa get more mature before harvesting it.

Coblentz added that it’s a good idea to not be “boxed in” by having only high-quality or low-quality forages available. That might mean making sure a farm has a place to store poorer feed.

He concluded by stressing the value of knowing just what quality of forage a farm has. He advised, “Routinely test forages and have rations balanced for energy and protein based on the appropriate heifer size and weight.”

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