How long to soak hay for horses is one of those questions that you hear asked by owners time after time, especially in the summer months, and there’s a lot of confusion around the subject. If your horse is overweight, dust sensitive, prone to laminitis or has equine metabolic syndrome (EMS), it’s probably something you’ve questioned at some point.
Horses in these categories may have excessive body fat, which can contribute to many other conditions, such as some types of colic and arthritis, and affects the body’s normal hormonal processes. Overweight horses are also more likely to have EMS, which is a condition that encompasses insulin dysregulation and predisposes horses to laminitis.
Tackling weight gain for these horses is a potential life-or-death factor, so we’ve asked independent equine nutritionist Clare MacLeod MSc RNutr to help you work out what’s best for your horse.
Why soak hay for horses?
The two main reasons are to reduce nutrient intake (when helping horses to lose weight) or minimise dust (for horses with respiratory problems).
Horses have evolved to spend most of their time chewing fibre, and to receive most of their daily calories from grass, hay and haylage. Often, forage oversupplies calories to horses, contributing to weight gain and obesity.
Soaking hay is an effective method for reducing its energy (calorie), water-soluble carbohydrate (WSC), or sugar and fructan content. This helps cut sugar and restrict calories from an equine diet.
Fructans are not the same as sugar, Clare explains. “They are sugar units joined with bonds that are fermented in the hindgut, rather than broken down by digestive enzymes.
“Research shows some fructan is broken down via bacterial fermentation in the small intestine. This is likely why it contributes to insulin response.”
This means fructans also contribute to laminitis.
How long to soak hay for horses: things every owner should know
The length of time you’d soak hay for depends on the desired result.
You might soak hay for 15-30 minutes to minimise dust for a horse with respiratory problems.
Soaking hay for 30 minutes to an hour slightly reduces its calorie and WSC content. However, the reduction may be insufficient to keep an obese horse in a calorie deficit, which is necessary for weight loss.
“Losses from soaking can vary,” says Clare. “It depends on factors including the composition of the hay, the amount of water used and the temperature,”
“Therefore, research that shows significant losses of WSCs in an hour or two cannot necessarily be relied upon in all real-life situations.
“In addition we are not soaking just for sugar and fructan loss but also for energy (calories). Reducing sugar without a significant reduction in calories will be insufficient for weight-loss targets.
“It’s not just sugar that horses get calories from – it’s fructan and fibre, too!”
Clare says water temperature can also influence nutrient loss.
“Losses are quicker in warmer water, so we might find we can soak for less time in summer, compared to winter, and in large volumes of water, so using as much as you can is key.”
Obese horses need reduced calories, but still need to chew to maintain gut health – small-holed haynets can make his ration last longer. Photo: Getty/Anja Janssen
Can you soak hay overnight?
Soaking hay for longer periods of 8–12 hours, or overnight, is considered suboptimal by some due to nutrient loss and the risk of fermentation.
But, according to Clare, a balance must be struck.
“Long soaking [10+ hours] reduces dry matter – the amount of actual hay, and fibre. Therefore, we need to take this into account and slightly increase the weight of hay to accommodate this loss.
“Increasing the weight of long-soaked hay by 20% can accommodate this, but the long-soak generally means we would be feeding hay at a higher rate anyway, since it becomes less nutritious.
“This is part of the benefit of long-soaking hay: it means we can feed more forage to our horse or pony while maintaining the calorie deficit they need for weight loss or healthy weight maintenance.”
As well as feeding more soaked hay, Clare adds that owners should use the bucket feed to ensure optimal nutrition.
“In terms of nutrient intake, we do need to carefully balance the diet with long-soaked hay,” she says.
“This can be done by adding a well-formulated feed balancer, such as a low-calorie compound concentrate fed at 100g per 100kg bodyweight, if there is no grass in the diet.”
Soaking hay overnight leads to elevated bacteria levels, but is better for a horse than obesity and its associated health risks. Photo: Philip Barker
Clare recommends considering long-soaking hay in cost-benefit terms for overall equine health.
“Although bacterial count can increase on long-soaked hay, there is no evidence showing this occurs to a level that is harmful to the horse. Plus, horses and ponies have been fed long-soaked hay for years with good results,” explains Clare.
“We should only soak for as long as necessary, but also realise that a slightly elevated bacterial count in hay is less unhealthy than chronic obesity with altered metabolic parameters, for example insulin dysregulation and/or laminitis.”
How long does soaked hay last?
As a rule, Clare says that soaked hay should be fed as soon as it has drained. Avoid re-presenting any uneaten quantity to your horse.
The quality of the hay to be soaked will likely influence its longevity.
“We should select only good hygienic quality hay for long-soaking,” she continues. “By this, I mean hay that is not dusty, with no signs of a high mould spore count (no fine smoke-like clouds that go airborne when you pull it apart).”
Other good hygiene practices to improve the life of soaked hay include:
- Soaking out of direct sunlight
- Using clean water for every soak
- Keeping soaking vessels and haynets clean
- Using the largest volume of water possible to speed up the effects of soaking
- Avoiding a long soak (for 10+ hours) unless you have to
- Remove and dispose of any uneaten portions
If the hygienic quality of your hay is suboptimal and there is no alternative, Clare says you could steam after soaking to improve the hygiene.
“With less than ideal hay to soak, using straw to replace some of the hay ration might be a better choice than a long soak,” she continues. “However, very dusty or mouldy hay should never be fed to horses.”
How long to soak hay for horses prone to laminitis
While we can’t put an exact figure on how long to soak hay for laminitis, Clare has a rule of thumb to follow.
“I recommend soaking for as short a time as possible, but with caveats,” she says.
“The soak time should also be as long as it takes for that horse or pony to be able to be fed enough forage to avoid more than a four-hour fast, whilst still receiving the correct amount of energy (calories) for the desired result.
“That might be for weight loss, or maintenance if they are at a healthy bodyweight, and to control the laminitis.
“So, it really does depend on the hay, and the individual horse or pony.”
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