American farmers have secretly been feeding their cows defective Skittles to avoid paying for corn.

That discovery was made public after a truck deposited hundreds of thousands of Skittles onto a rural road. All of them were in one colour and without the trademark "S" on them and, after they were found, the police were forced to ask highway cleaners to get rid of them.

Unknown to many, the practice has been going on for years, according to experts. Not only are Skittles cheaper than corn – especially when bought for a lower price because they are defective – they could even provide other benefits over traditional feed.

As well as clearing up the mystery of why so many skittles appeared on the road, the crash has helped shed light on feeding practices that had until now had only been known by farmers.

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The practice is healthy and might even be more environmentally friendly, according to those who use it.

Joseph Watson, owner of United Livestock Commodities, told LiveScience in 2012 that feeding cows sweets "actually has a higher ratio of fat [than] actually feeding them straight corn", and that it has "all the right nutrition".

And John Waller, a professor of animal nutrition at the University of Tennessee, told the site that it was likely to be more green because it keeps "fat material" from simply going into landfill.

The practice of buying in defective or unneeded food to feed to animals go back for decades. But it is thought to have picked up around 2012, when corn prices rocketed up and farmers needed a cheaper way of feeding their animals.

As well as revealing the mostly secret feeding practices, the use of Skittles helped solve the mystery for police in Wisconsin, where the crash happened. The Dodge County Sheriff posted on Facebook about the strange crash.

"At 8:51pm on Tuesday night, the Dodge County Sheriff's Office came across unusual items that were left in the road," it wrote. "Hundreds of thousands of Skittles were spilled on County Highway S near Blackbird Road. It is unclear who may have spilled the skittles on the road. The Dodge County Highway Department was asked to clean them off the road.

"While we don't know who did this, it is certainly clear that it may be difficult to "Taste the Rainbow" in it's entirety with one color that likely fell off the truck!"

(Dodge County Sheriff&#039;s Department) (Dodge County Sheriff's Department)

Commenters on the post were shocked to find that the skittles were being used as cow feed and worried that it would change the quality of the meat.

After it emerged what had happened, the Sheriff's Office posted an update.

"The Skittles were confirmed to have fallen off the back of a truck," it wrote. "The truck was a flatbed pickup and the Skittles were in a large box. Due to it raining at the time, the box got wet and gave way allowing the Skittles to spill out on the roadway. It is reported that the Skittles were intended to be feed for cattle as they did not make the cut for packaging at the company. In the end these Skittles are actually for the Birds!"