If you’ve got a horse that gobbles up his feed, you might be able to slow him down—improving his physical and mental health in the process—by adding chopped forage, or chaff, to his meals. The key, says a team of international researchers, is adding enough chaff to make a difference.

In a recent Australian-U.K. study, blends including at least 15% chaff significantly increased horses’ feed consumption times. Why is this important? Because “guzzling” meals, especially concentrated cereal-based feeds, can put horses at risk of gastrointestinal, metabolic, and behavioral problems such as choke and colic, the researchers said.

“Using the appropriate type and levels of chaff addition can be a valuable management tool for owners and should be considered to help slow intake rate and potentially extend the time spent foraging,” said Patricia Harris, MA, VetMB, PhD, Dipl. ECVCN, MRCVS, head of the Equine Studies Group at the WALTHAM Petcare Science Institute in Waltham on the Wolds, U.K.

Chaff’s Effect on Consumption Rates

Chaff is often marketed as a healthy forage solution for senior horses because it requires less chewing than long hay. However, it can help prolong consumption times of grain-based or pelleted diets that horses would otherwise eat very quickly.

Some owners already use chaff for this purpose (for 95% of Australian racehorses, for instance), but data on chaff type and quantity are lacking, said co-author Martin Sillence, BSc(Hons), PhD, professor of biological sciences at Queensland University of Technology, in Brisbane, Australia.

In a series of four studies in Australia—three on the same 12 geldings and one on 71 horses of mixed sexes and breeds—Harris, Sillence, and their colleagues explored various factors, including the addition of chaff, affecting rate of ingestion (ROI). They compared two chaff lengths (European lengths of about 4 centimeters versus Australian lengths of about 2 centimeters) cut from the same bale of straw. They also looked at factors such as body weight, breed, gender, age, amount of exercise, meal size, and palatability to compare their effects on ROI.

Quantity Matters

The scientists found that adding 15% chaff to a ration of oats prolonged feeding times by up to 50%, Sillence said. In a previous study, adding 6% chaff did not affect ROI, he noted.

That 15% is based on a meal of oats, though, Harris said. For other feed types, the amount could vary. For pelleted feed, for example, 20% chaff might be better, she said. Depending on the country, some commercial feed preparations include upward of 15% chaff, she said. Owners can also purchase bags of pure chaff, called chopped forage in the U.S., and mix it into their horses’ feed.

The researchers didn’t detect any differences in feeding times between shorter and longer cuts of chaff, said Sillence, possibly because the two lengths only differed by 2 centimeters. Longer chaff might slow feeding even more, he theorized.

Exercise had no significant effect on feeding time, either. The study horses, however, participated in a wide variety of exercise programs, the team said, making it difficult to distinguish trends.

Meal size (when feeding oats alone) didn’t affect ROI, nor did gender or age. The team added molasses to make meals more palatable, but it didn’t cause horses to consume their cereal rations any faster—probably because oats themselves are “already very palatable,” they said.

The researchers found that, on average, heavier horses ate faster than lighter horses but cautioned that heavier horses don’t always eat faster, and many factors can contribute to rate of intake, such as breed, environment, and the individual. “In our experience some small ponies can be very greedy gobblers,” said Sillence.

Overall, body weight might not be the most defining aspect across breeds for intake times, said Harris. “Perhaps most importantly, there are wide individual differences in rate of intake,” she said. “Some animals are perhaps very feed-orientated, and others are not. Head and jaw size might also be important factors. Plus, there can be effects of feeding history (such as being on a restricted diet or fed free-access) and the type of feed being fed. Previously, we have shown wide variation in the rate of intake depending on the feed type.”

Speed Changes During Meals

Sillence said an unexpected finding was that the speed at which horses ate their food evolved throughout the meal. “We did not anticipate how rapidly the rate of intake changes during the course of a meal,” he said, adding that this can lead to confusion and conflicting results in studies on how fast horses eat. “Clearly there is need for some sort of standardization when testing the ROI for different feeds.”

Based on these findings, the team said owners should consider slowing their horses’ consumption rates early in the meal. This could include offering forage first to reduce hunger levels, feeding fast eaters before other horses, or separating horses to prevent them from eating fast because they’re competing with others.

Take-Home Message

Whether it’s adding chaff, separating horses, feeding hay first, or mixing feed with hay, owners have options for extending mealtimes to improve their horses’ health and welfare, the researchers said.

“Anything that slows down the rate of intake and keeps a horse occupied is a good thing in my view, given that meal-fed horses spend so much less time feeding than their counterparts who graze in the wild,” said Sillence.