Thirty cents per ton is pretty cheap quality assurance. That's the cost of 2 lb. of iron oxide, an inert feed additive that turns feed red.

North Carolina pork producers are using iron oxide to distinguish feeds for different groups, adding it primarily to sow feed, but it has a place in any diet containing costly ingredients or medications which require withdrawal before slaughter, says David Funderburke, a nutrition consultant from Warsaw, NC.

"The more diverse the production system, the greater the chance for error," notes Funderburke, who consults for some of the country's largest hog operations. "A colorant has a place wherever withdrawal times are critical. Even the 100-sow producer who buys from a feed company may want to color the feed, because that producer is not the person mixing it."

Iron oxide comes in two forms: natural and synthetic. The natural form of iron oxide is cheaper, but provides a less-distinct color than synthetic, which has a more potent pigment. Funderburke typically adds about 2 lb. of the natural iron oxide to each ton of complete feed at 15 cents/lb. With synthetic iron oxide, only a pound or less is needed per ton, but the cost would be about $1.50.

Enough iron oxide needs to be added to be able to notice a color difference. Which form producers choose depends on the degree of color desired.

An approved feed additive, iron oxide is safe, with no known hazards. Iron oxide should not be confused with iron carbonate or iron sulfate, which are sources of digestible iron in the ration. Iron oxide has no nutritional value, notes Funderburke. And, both natural and synthetic iron oxides are dusty, he adds.

Ken Purser, nutrition and technical services manager with Prince Agri Products Inc., an iron oxide manufacturer, points out that coloring or marking feed has gained interest in the last three or four years. "It has a lot to do with pork quality initiatives and awareness on the part of producers in observing proper withdrawal times," notes Purser. "Plus, producers are pushing production systems harder, so it's important to have the correct diet in the feeder at the right time.

"The number of employees involved in large, integrated systems can also make communication difficult," he adds. "Marking makes it much easier for everyone to determine if the proper feed is being fed."

Funderburke says adding the iron oxide is one of the cheapest ways to prevent mistakes. "Lactation and gestation feeds can have similar ingredients but as much as a $20/ton difference in price, so we'll use iron oxide in lactation feed (to differentiate it)."

Another place to use a marker is when feed with a withdrawal requirement is fed sporadically. Herds with enteric problems, for example, may add carbadox, which was recently approved for feeding until 42 days before market. These antibiotics may be fed at a higher, disease-control level, or reduced to an amount conducive to growth promotion.

"At times, we may pulse the additive into the ration for just a few weeks at a time when there's a flare-up, which would make it even more critical to mark the feed," Funderburke explains. "Employees are aware not to ship pigs from pens with red feed, even if they're culls."

Monitoring Tool "It's a way to monitor - to make sure the correct feeds are going to the correct animals," Funderburke says.

"Anyone with reservations about delivering medicated feed to the wrong finishing building, for example, should consider using a marker."

Many feed mills in North Carolina are self-owned by integrators with 15,000 sows or more, explains Funderburke. The mills run 12-18 hours/day, producing 1,800 to 2,000 tons of feed each week. The larger the mill, the more segmented the production system, with each segment run independently, he notes.

"There are many opportunities for error in large, integrated production systems," Funderburke adds. To help delivery people avoid mistakes, feed bins and farms are usually numbered. Some bins carry magnetic, color-coded signs. If the sign is red, they'll know to deliver red feed."