feed mill equipment
Q.I recently bought a bag of feed for my horse and was surprised to find quite a number of pieces of what appeared to be whole corn. I’ve fed this feed for some time and have never found corn in it before. I checked the label and the formulation has not changed—corn isn’t listed in the ingredients. Why is this corn in my feed?

—Via e-mail

A.Feed mills sometimes use shelled corn to flush their milling equipment to remove residue from previously manufactured feeds. Mills have several ways they keep the insides of their equipment clean and residue-free. They can physically clean out the equipment, use sequencing, flushing, or a combination of these methods.

Mill Cleaning Methods

Physically cleaning equipment involves shutting the mill down while personnel sweep, wash, disinfect, and scrape out equipment at accessible areas. This cleaning method is likely the most effective at preventing residue carry over from previous feed manufacturing, but it’s costly because it requires considerable equipment down time. Good manufacturing practices stipulate mills must be designed in such a way that cleanout procedures can be used as needed.

Most manufacturers will conduct physical equipment cleaning on a scheduled routine, whether that’s monthly, semi-annually, or annually. Some firms do it on an as-needed basis or choose to physically clean certain areas more frequently (e.g., when those handling liquid ingredients become “gummed up.”)

Flushing feed manufacturing equipment involves taking a known amount of a common feed ingredient and running it through the mill, most commonly after manufacturing medicated products. The flush material runs through the entire system, loosening and collecting any leftover feed. Flush material is typically a single ingredient; mills often use ground corn, although shelled corn and other ingredients are options, as well. Once it has worked its way through the entire system, the flush ingredient is stored for future use in a feed.

If the system is being flushed after a medicated feed is produced, the stored flush ingredient must be labeled as such and used in feed containing that same medication. Feeds containing medications should only be fed to animals for which that medication will not be harmful; one example is the antibiotic monensin, which is used in cattle feed but is toxic to horses.

Other Measures

Cleaning isn’t the only method mills use to prevent contamination. Sequencing ensures horse feed doesn’t contain medication from previously milled medicated feeds. The process involves running feeds in a specific order. For example, the mill might follow production of a cattle feed with monensin with an unmedicated cattle feed and, if the mill makes chicken feed, an unmedicated run of chicken feed might run next. Because monensin isn’t harmful to chickens, contamination wouldn’t have health implications should any contamination occur. Mills should never run horse feed immediately after any feed containing medication that could be harmful to horses.

Mills are required to keep very detailed operating manuals that dictate what feeds can be run in what order. The more sophisticated mills I’ve visited have software overrides that won’t allow these manufacturing sequences to be broken. Manufacturers must also keep records documenting which feeds were milled in what order.

Some mills use a combination of sequencing and flushing; this involves sequencing feeds and then flushing equipment prior to running horse feed. Research has shown that, when conducted properly, both sequencing and flushing can effectively remove possible contamination from milling equipment.

Ideally manufacturers make horse feeds in lines dedicated solely to unmedicated products. However, even these feeds might occasionally contain flushing material if mills use flushing as a method to physically clean the equipment of ingredient debris.

Check Feed Closely

Typically, the first bags of feed manufactured after lines are flushed are set aside and not sold, because they might contain small amounts of the flushing ingredient—likely the corn in the case you describe. Occasionally, however, these bags do make it into retail stores and are sold. In my experience feed stores and companies are always willing to take back such feed bags.

If you do take a bag back to exchange it you might want to open the replacement bag at the store to ensure that it, too, doesn’t contain flush material, because bags on a pallet will have come off the line one after another. I suggest looking at the batch number on the bag and try to get a replacement bag from a different batch.