Hay is for horses

GUELPH – Hay may seem like the simplest part of a horse’s diet, but as University of Guelph (U of G) professor Dr. Anna Kate Shoveller explains, it’s the foundation of equine health and far more complex than it appears. 

Horses are designed to graze for 14 to 18 hours per day, relying on a steady flow of forage to protect the stomach, fuel the hindgut and support overall wellbeing. 

In a U of G study, Shoveller and her team examined how soaking or steaming hay changes it, how horses respond, and why the “right” choice depends on the horse.

The study found when horses used to eating dry hay were offered soaked, steamed and dry hay side by side, horses consistently ate less of the soaked hay.

The research team also found soaking washed out certain proteins and sugars, while steaming proved better at conserving them. 

Shoveller said the most important decision in feeding hay is the quality of the original hay, not whether it is soaked or steamed. 

For horses prone to obesity, selecting hay with a low nutrient profile is usually advisable, whereas nutrient dense hay is better for the highest performing horses. 

Nutritional changes

Soaking hay causes the loss of soluble protein (SP), potassium and non‑structural carbohydrates (NSCs).

SP is the portion most readily digested – performance horses rely on it to build and maintain muscle for training and recovery. 

In the study, soaking hay for 30 minutes reduced potassium by 41 per cent, a key consideration for athletic horses that lose electrolytes in sweat.

NSCs are the easily digestible simple sugars and starches in hay that supply fast-energy in contrast to the energy produced from fermenting structural carbohydrates, such as the components of total dietary and crude fiber, or structural carbohydrates. 

For overweight horses, it helps to control the glycemic index to avoid big increases in blood glucose when they eat larger portions. 

Soaked hay can be practical for horses with metabolic syndrome and for horses that are easy keepers. 

For performance horses, young horses or old horses struggling to meet nutritional needs, feeding steamed hay can be supportive. 

While soaking hay is often used to reduce sugar for metabolic or overweight horses, Shoveller emphasizes that sugars are not all that is washed away in the process. 

Soaking also removes a wide range of other nutrients including minerals and micronutrients that would otherwise remain available in dry or steamed hay. 

Soaking hay is a useful strategy for horses where sugar reduction is desired, such as managing metabolic syndrome, insulin resistance or obesity. 

However, owners need to understand they’re also reducing many nutrients the horse requires. 

When soaked hay makes up a large portion (or all) of the forage ration, she advises adding a ration balancer or appropriate supplement to replace the vitamins and minerals removed during soaking. 

A caveat for soaking hay concerns time, as drenched hay quickly grows mouldy. 

For most situations, soaking should be kept to the minimum effective duration and fed promptly afterward. 

Many equine nutritionists recommend soaking hay for 15 to 30 minutes and no longer than one hour. A University of Minnesota study notes 30 minutes in warm water or 60 minutes in cold water is effective for reducing carbohydrates. Shorter soaks have also been shown to have an impact, with 15 minutes resulting in significant decrease of sugar levels in some types of hay. 

Before soaking hay, it is advisable to talk with an equine nutritionist to discuss desired results and ensure it’s the right strategy for the horse and any lost nutrients are balanced appropriately. 

Respiratory concerns

Reducing particles horses inhale at meal time can improve respiratory health. 

Soaking and steaming hay reduces dust, as long as the dust isn’t coming from mould that produce mycotoxins, Shoveller said. That stipulation is key: if “dust” is actually mould spores, no amount of wetting the forage will solve the underlying problem. 

“Mould and mycotoxins can be extremely deleterious to horses, and even small amounts can reduce performance,” cautions Shoveller. She recommends testing dusty or musty hay for mould and mycotoxins, or discarding it. 

Good storage practices (dry, ventilated, off the ground), careful selection, and minimizing indoor dust sources (bedding, traffic, wetting aisles before sweeping and sweeping when there are no horses in the barn) all support healthy air. 

For horses that are especially reactive or when caretakers need the most controllable, low‑dust option, processed forage such as pelleted or extruded hay can be the best option. 

“Those products are checked for mould and mycotoxins, and the pelleting or extrusion process reduces the ability for mould to grow,” Shoveller said. 

Pellets and cubes don’t replace the need for good ventilation and overall dust control, but they can cut down on inhaled particulates at feeding time while maintaining nutritional consistency.

For horses with respiratory problems, outdoor pasture, where there is less dust, is usually the best option.  Group turn out 24/7 also helps to meet the behavioural needs of horses.

Automated hay

Horses are built to graze near constantly and to have a steady trickle of forage moving through the stomach and into the hindgut.  

That slow, continuous flow matters because the equine stomach secretes hydrochloric acid all the time, not just at meal times. Frequent, fibre‑rich chewing supports the production of saliva, which is nature’s antacid for the horse’s stomach. 

When long gaps occur without available forage, the stomach becomes more acidic, significantly raising the risk of ulcers.

While ad-lib, unlimited access to hay meets the need for constant gut fill, some horses overeat and are therefore at risk for obesity.

A new study on automated hay feeders has received funding from Equine Guelph at the U of G. Automated feeders mimic natural grazing, feeding little and often  during the day and overnight.

An automated schedule may offer a middle path of frequent, predictable access that protects the stomach and supports hindgut fermentation, while avoiding unchecked intake.  

This could help busy barns maintain healthy equine digestive systems, especially through the hours where staff are not on site. 

The project was set to begin June 1 in the Okanagan region of British Columbia with Dr. Katrina Merkies, Dr. Megan Ross and Alayna Riddell.  

“The main focus of the study is to look at social dynamics and voluntary physical activity in relation to providing hay from automated feeder,” Merkies said. 

Automated feeders can be loaded with a hay bale and programmed to open multiple times, targeting a percentage body weight in total daily forage to be dispensed and adjusting the duration based on how quickly the  hay is consumed.  

Ross said the researchers will “monitor eating and drinking frequency, social and agonistic interactions, and use a 24/7 halter‑mounted sensor to log distance travelled and activity patterns.” 

When first introduced to the automated feeder, horses may learn to anticipate feeder opening times and an increase in social interactions may occur in response to the limited resource. 

However, once horses learn that forage will be available regularly and often, displacements at the feeder should taper off. 

The team plans to compare findings from automated feeding to those recorded during unlimited hay access.