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The Slow-Feeding Movement

In their natural setting, horses typically graze between 14-16 hours a day.  This has anatomically designed them to be best suited for small, frequent forage meals throughout the day. 
However, in today’s setting with modern management strategies, many horses have limited access to forage due to meal feedings and increased time being stalled. These management changes have led to alterations in digestion as well as dysregulations of metabolic patterns including glucose, insulin, and cortisol.  So what does this mean for your horse?  It means there is a higher prevalence of physical conditions like colic, stomach ulcers, laminitis, insulin resistance, obesity, and metabolic syndrome in the domestic horse.  Meal feedings and increased stall time have also been linked to more mental/emotional disturbances that can develop into stereotypic behaviors including cribbing/wood chewing, stall weaving, and head shaking (read more about stereotypic behaviors HERE from our blog archives).  All of which can lead to poor performance and un-thriftiness.

So what’s to be done about all this?  The Slow-Feeding Movement may provide an answer.  Slow-feeding mimics a more natural feeding pattern without the potential for excessive calories that can occur when providing forage ad libitum without any form of restriction.  Generally, slow-feeding is accomplished using a hay net or grazing box.  

Horses must use their agile, prehensive lips to grasp bits of hay and pull them free.  This action imitates a horse’s natural grazing motion to help promote characteristic feeding actions as well as increase time spent foraging and eating.

First, a little bit of digestive anatomy and physiology to help you understand why prolonged grazing time is desired for horses.  Horses are considered non-ruminant herbivores and hindgut fermenters.  The digestive tract of the horse is divided into two sections, the foregut and the hindgut.  The foregut consists of the stomach and the small intestines.  In this section of the digestive tract, enzymatic action breaks down the majority of crude protein and simple carbohydrate matter like the starch in grain.  For their size, horses have relatively small stomachs with capacity generally being about 2 gallons.  While a horse is foraging and chewing, sodium bicarbonate is being released in saliva to help the digestive process and act as a buffer for the acidic environment of the stomach which produces hydrochloric acid, or HCL.  A horse’s stomach generally empties within half an hour as the rate of passage of feed is very fast in the foregut.  Without the ameliorating effect of the sodium bicarbonate, stomach acid can build and can lead to the development of ulcers when the stomach remains empty for long periods of time.  Increasing time spent eating with a slow feeder will help keep stomach acidity in check, and may help prevent ulcers in your horse.

The second section of an equine’s digestive tract is called the hindgut and it consists of the large intestines which contain the cecum and the colon.  The horse has the largest and most complex large intestine of any domestic animal, and it makes up about 60% of the horse’s digestive tract.  The large intestines are designed to utilize plant fiber, so this is where digestion of forage takes place. Fiber is digested via microbial fermentation in the cecum - billions of microbes including bacteria and protozoa secrete enzymes to break down plant fiber.  The rate of feed movement in the hindgut is much slower because the colon folds back on itself many times and its diameter changes throughout its length.  This predisposes horses to digestive upset, i.e. colic, when nutrient flow is abnormal.  As mentioned previously, abnormal flow can be caused by meal feedings and decreased grazing time as well as large concentrate, or grain, meals.  Providing slow-feed options can help create a more normal and consistent flow of feed through the digestive tract to reduce risk of colic and other digestive upset.

In a study performed at the University of Minnesota in 2014 and published in the Journal of Equine Veterinary Medicine, the optimal size for holes in a hay net to prolong consumption time ranged from 1-1.75 inches.  The study fed horses from the ground or from hay nets with large (6 inches), medium (1.75 inches), or small (1 inch) sized holes and recorded the amount of hay consumed within a 4-hour time period. The mean percentage of hay eaten was 95, 95, 89 and 72% for the control (fed on the ground), large net, medium net, and small net respectively.  They were able to break it down farther to calculate that the horses ate 3.3, 2.9, 2.4, and 1.9 pounds of hay per hour.  
The horses in the study were able to consume all hay from the ground and large hole net during the 4-hour feeding period, but not all horses finished their hay meals when fed from the medium and small nets. A subsequent analysis was performed and discovered that horses fed from the medium nets took just over 5 hours to consume all the hay while horses eating from the small nets took 6.5 hours to consume their meal.  Both the control and large net groups had consumption times of 3.2 and 3.4 hours.  This means that horses fed using the medium or small sized nets took almost twice as long to eat their meals.  That’s three more hours that a horse has to happily munch away instead of standing around with nothing to do.

In another study performed at the University of Minnesota, researchers fed treatment horses using slow-feed nets and fed control horses off the ground, and then measured their postprandial (after meal) metabolite and hormone patterns.  Specifically glucose, insulin, and cortisol were measured.  Overall, glucose and insulin within the slow-feed group had decreased peak levels, but otherwise were comparable to the ground-fed group. Conversely, cortisol, or stress-hormone, levels were significantly increased within the ground-fed horses.  This was hypothesized to be caused by the control horses finishing their meals faster and then being within sight of the net-fed horses that were still eating.  These results indicate that slow-feed nets may provide more consistent or homeostatic levels of postprandial metabolites and hormones.

Because food is a very high drive activity for horses they often become anxious or stressed when that activity cannot be performed.  This is why you see exaggerated types of stereotypic behaviors like cribbing, stall weaving, head bobbing, and teeth raking as well as higher emotional states at feeding times.  As was mentioned in the above study, horses that were not able to eat and could still see other horses eating tended to have higher cortisol levels. The same higher cortisol/stress levels could be found with horses that are anticipating feeding times as well especially when those feeding times only occur 1-2 times per day.  Giving horses something to do by extending their time spent eating can result in more content horses.

Besides the health benefits, feeding out of a slow-feed net or grazing box can help reduce waste.  When hay is fed on the ground, or even in some feeders, it is often trampled on and subsequently defecated/urinated on leading to a lot of wasted hay.  It is estimated that up to 40% of a large round bale can be wasted when not contained in any type of feeder.  Feed waste not only happens with hay, but can occur when feeding grain as well.  In a study performed at Texas A&M University, researchers discovered horses fed grain out of “Pre-vent” buckets dropped significantly less feed from their ration when compared to buckets or flat tubs.  “”Pre-vent” buckets are designed with “compartments” or “cups” at the bottom of the bucket to make horses work to get grain out of the cups using their lips and tongue.  
The most wasteful horse in the study only lost 8.7% of his feed when fed from the “Pre-vent” bucket as compared to 32.8% lost from a bucket, and 26.2% lost from a tub feeder.  That’s almost 20% more grain staying in the bucket!  The “Pre-vent” design is also supposed to help prevent choke and sand colic by reducing the speed of consumption and reducing the amount of feed dropped and then eaten off the ground.  In the study, horses that were fed from the cup feeders spent significantly more time eating as compared to the regular buckets or flat tubs.  On average, it took horses fed from the cup feeders around 30 minutes to finish their grain meal as compared to less than 20 minutes when fed from the other buckets.  

Some other fun options to slow your horse when eating and provide environmental enrichment include the Nose-It!® Ball for pellet feed or treats, and the Amazing Graze® treat dispenser.

If you are thinking of making the switch to slow feeders, just know there may be some transition time.  The research from University of Minnesota found that, on average, it takes four feedings for horses to feel comfortable eating from the nets.  It is generally safe to start with 1.75 inch hole nets and then, if needed, you could reduce the size down to the 1 inch sized nets.  However, when you first introduce slow-feeders it is recommended to provide additional hay only in the slow-feeders and feed the normal amount in the same way you had been previously, be it in feeders or on the ground.  Then you can transition slowly to using slow-feed options for all the hay.  There are slow feed nets for small squares, large squares, and large round bales, so whatever type you feed there is a net for it.  It is also important to note when using nets in a group setting to always set out more nets than there are horses.  This is to prevent lower pecking order horses from being kept from the feed and allow all horses to have their own space.  Having multiple nets available will also promote more movement for your horses as they wander from one net to another.

Check out some of the links provided below to learn about the varying options for slow-feed nets and boxes to find the best fit for both you and your horse.  Included is our tried and true “NibbleNet®” for a net option and, if you're handy, there's a link on how to build your own grazing box.  The studies mentioned in this blog are also listed below for your perusal. If you have any additional questions or comments about the slow feeding movement please feel free to contact any of the doctors at ACIC. Thanks for reading!

Hay Chix (local MN company too!):


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