Ash is often considered a minor player in dairy ration balancing. But overlooking ash content when formulating milk cow diets can cause big-time problems.
More specifically, too much ash in forages can hurt ration energy levels, warns Pat Hoffman, a University of Wisconsin extension dairy specialist.
Ash in forages basically comes from two sources. It's a component of macro- and microminerals — like calcium, potassium, phosphorus and magnesium — in plants. External sources of ash include soil (dirt, sand bedding, etc.) that can get mixed in with forage during the harvesting, storage and feeding out processes.
For legumes, typical ash content is in the 8-10% range. But Hoffman and his co-workers at the University of Wisconsin soil and forage analysis lab in Marshfield have been seeing many samples around 20% and even higher.
“That's an awful lot of unwanted ash any way you look at it,” says Hoffman. “Suppose you have a ration calling for 25 lbs of haylage (dry matter). At the 10% level, 2.5 lbs of the total dry matter fed to the cow would be mostly normal mineral contents. At 20%, you're talking 2.5 lbs of normal mineral plus 2.5 lbs of dirt per cow per day.
“While there have been few dairy research trials in this area, it is highly likely that cows do not milk well when fed dirt,” he adds.
The problem on the feeding end: Ash doesn't contribute any calories (energy) to the diet. Instead, it displaces nutrients on an almost one-to-one basis.
“So if the ash content of a feed sample is five units higher (than the normal 8-10%), the TDN content of the forage is five units lower than you thought it would be,” says Hoffman.
Chris Hallada, dairy nutritionist with VitaPlus Feeds, has also observed a trend toward higher ash levels in forage samples for some of the Minnesota and Wisconsin herds she works with.
“We've seen it as high as 15% of total dry matter,” she notes. “At that amount, there's a significant drop in forage energy available to the cow.”
The problem can be especially pronounced in wet-weather years.
“With a hard rain, you get some soil splashing up onto the plant,” she says. “Also, the alfalfa gets matted and soil gets taken up with the hay during raking.”
Inadequate or improper storage can also play a role in raising ash levels.
“The important thing is to store forages on a hard, clean, dry surface,” says Hallada. “If you don't, and the feeders aren't careful, you can end up getting an awful lot of dirt in the feed when the TMR is mixed.”
Hallada and Hoffman agree that testing for ash levels is probably the single most important step producers can take to head off problems.
“Many producers probably don't realize that they're even having a problem,” says Hallada. “But a lot of times, after you get results back from the lab, you'll go out, look at the feed in the bunk and see dirt or grit that you hadn't noticed before. Once you're aware of the problem, you can start looking for things that might be causing it and take some corrective steps for the future.”
Many, but not all, feed companies and commercial labs now routinely include ash content as part of each forage analysis. Some companies charge an additional fee to check ash levels.
“Labs don't need sophisticated equipment,” says Hoffman. “So they usually don't charge more than a couple of bucks to run the analysis. But from the dairy producer standpoint, having it done can prove to be very worthwhile.”
Forage Seminars Set For Expo
Forage seminars will again be part of the World Dairy Expo, this year set for Oct. 2-6 in Madison, WI.
The seminars will take place at the World's Forage Analysis Superbowl display area in back of the Arena Building at the Alliant Energy Center. They'll be presented by forage experts from the U.S. Dairy Forage Research Center, University of Wisconsin, University of Illinois and Michigan State University.
Dates and topics are as follows:
Oct. 3, 10:30 a.m. — Role of Lactobacillus Buchneri in Silage Preservation.
Oct. 4, 10:30 a.m. — Packing Bunkers & Silage Tubes: Density Goals. 1:30 p.m. — The New Relative Forage Quality Index: Animal Allocation & Forage Breeding.
Oct. 5, 1O:30 a.m. — NDF Digestibility of Corn Silage, Haylage and Hay: Laboratory & NIRS. 1:30 p.m. — NDF Digestibility: Impact on Cow Performance & Influence of Forage Crop.
Forage experts also will be available to answer questions Thursday through Sunday, from 9:30 to 10:30 a.m. and 2:30 to 3:30 p.m.