If you think you're feeding a well-balanced ration but are disappointed in your herd's production, ash could be the culprit.
Ash is one of the most difficult ration components to get a handle on, yet it can lurk in the background as a chronic cause of unrealized performance. It's a necessary and normal part of any ration, but the total ash content must be kept within a healthy range. Exactly what that range is, however, is debatable.
What is ash? It's the total mineral content of a ration, including unnecessary mineral debris, normal mineral content of forages, and mineral supplements. If total ash content is excessive, feeds laden with soil or excessive mineral supplements may be the problem.
Both the normal ash content of a TMR and of legume-grass forages is close to 7%, according to Pat Hoffman, extension dairy scientist at the University of Wisconsin Marshfield Ag Research Station. Ash content of corn silage is about 4-5%, and a typical vitamin-mineral packet is 90-100% ash.
A range of 6-9% total ash in the ration is probably a good benchmark to use, says Hoffman, but no one quite knows for sure what range is safe. What scientists do know is that for each 1% increase in the total ash content, the TDN content of a ration drops 1%.
It's not uncommon to find TMRs with ash contents greater than 15% during lab analysis. “A TMR with 16% ash means there's a lot of potential soil contamination going on,” says Hoffman.
A lot of feed companies guarantee a maximum ash content, says nutritionist Mark Aseltine, Atascadero, CA. When balancing a ration for a client, Aseltine pays little attention to ash.
“Excessive ash is really an issue that needs to be taken care of on the farm,” he says.
As long as the individual feedstuffs don't exceed their ash maximums, total ash should not be a problem. Inspecting loads of forages for dirt and other debris and rejecting contaminated loads is the first safeguard a dairy can take against too much ash.
For large dairies taking frequent feed-ingredient deliveries, that can be a daily chore.
Some feeds are naturally dirtier than others. For instance, almond hulls tend to be dirty because of the way they're harvested and thus need to be inspected more closely. If producers visually inspect purchased forages when they're delivered, store them properly and handle them correctly when mixing and feeding, ash shouldn't be excessive.
For those who grow forages, problems can occur at any step in the process. For instance, using sand-laden manure between cuttings can elevate the ash content of the harvested crop, Hoffman notes. So can storing forages on earthen bases or dragging soil into bunkers and piles when feeding.
Once a feed is contaminated with sand, soil or excess minerals, not much can be done, he says.
If it's purchased, send it back, says Aseltine. If it's home-grown, feed it in small quantities to keep total ash at a reasonable level, or feed it to dry cows.