After water, fibre is the most important component of the equine diet. When insufficient fibre is fed, it has been shown to lead to hindgut acidosis, gastric ulcers and stereotypic behaviours (e.g., cribbing).
Most owners understand that it is critical for horses to have ample access to forage to meet their fibre requirement, whether it is hay, or pasture. However, it is unfortunately common that the change between forage types is poorly managed leading to gastrointestinal (GI) health problems that often could have been prevented.
The Nutrient Requirements of Horses (2007), states that all feed changes should be made gradually which includes concentrates, hay, pasture, supplements and preserved forages (e.g., hay cubes). Understanding how to safely transition between forage types is an important aspect of nutritional management.
At this time of year, horses frequently experience numerous forage changes. Whether they are transitioning to pasture, from pasture back to hay as that pasture is grazed, or from their current hay to the newly harvested batch – caution must be exercised.
This article will explore why forage transitions matter, how to manage them effectively, and tips to minimize your horse’s risk of GI upset.
Why Gradual Transitions Matter
When forages are consumed, they are digested via microbial fermentation in the hindgut of the horse. The hindgut is home to billions of microorganisms that provide the horse the ability to effectively digest and utilize forages as the primary component of their diet.
When there is a change in the forage provided to the horse, it will alter the microbial population in the hindgut. This turnover can take several weeks as the microbial population adjusts and adapts to the differing diet. When abrupt changes are made, it shocks the microbial population, and many of the beneficial microorganisms die. Research has suggested that abrupt changes in the type of forage fed is a primary contributor to increased colic risk. By making the changes gradually, you are allowing the microbial population time to adapt to the new diet.
Nutritional Content of Hay
I often find that this aspect of equine nutrition is overlooked when it comes to hay. Concentrate and pasture transitions are almost always transitioned slowly, but with hay batches appearing similar, they are frequently changed abruptly.
It is critical to remember that the nutritional content of hay will differ, even hay that has been cut from the same field. Variables such as weather, soil nutrient content, plant species, and harvesting conditions are just a few of the many factors that influence the nutritional content of forage.
For example, analysis of the 2024 Balanced Bay hay data revealed that the crude protein content of hay harvested in Ontario ranged from as low as 3.6% to over 20% on a dry matter basis. I regularly test hay for several large facilities, and even when the hay is the same type (e.g., first cut), and sourced from the same farmer, its nutritional profile often varies significantly between batches. Hay that looks similar, or comes from the same supplier, likely differs in nutritional value, and should never be switched abruptly.
Transitioning Timelines
Ideally, when a new batch of hay comes in, we want to mix it with the current hay and slowly increase the proportion over the course of a couple of weeks. Using a slow feeder or hay nets can be beneficial during these transitions to reduce the horse’s ability to separate the two types of hay.
A recommended schedule is:
When Ideal Isn’t Possible
Now, this recommended transition period may not always be feasible. It is important to understand the ideal, and work within the restrictions of your situation to do the best for your horse. For example, when I recently moved my horses, I was unable to take a full 2-3 weeks of their current hay with me. So, to avoid GI upset, and lessen the shock on their GI tracts, I made sure to take 5-6 days worth of their current hay and transition them over the course of 10 days.
Another strategy that I find to be effective is to choose a preserved fibre source that can easily be brought with your horse and fed daily as a consistent source of the same type of fibre. This tactic is beneficial as it provides fibre consistency during travel, reduces the variability in nutrient intake when forage is changing and promotes hydration when soaked.
There are a variety of options when adding a preserved fibre source to your horse’s diet. Beet pulp, hay cubes, hay pellets, or a complete feed are all options. The right match for your horse will depend on their individual nutritional requirements.
Take Home Message
Let this article be your reminder to take a step back and critically consider the impact that hay changes can have on your horses GI tract. Whether you’re travelling to a show and your horse will be on different hay while housed there, transitioning from 2024 to 2025 hay, or putting your horse back on hay once their pasture is eaten down, take the additional week to exercise caution with a slow transition to reduce the health risks.
If you have any questions on how to optimally manage forage transitions, please email balancedbaynutrition@gmail.com
By: Madeline Boast, MSc, PAS
References:
Cavallini, D., Penazzi, L., Valle, E., Raspa, F., Bergero, D., Formigoni, A., & Fusaro, I. (2022). When changing the hay makes a difference: A series of case reports. Journal of Equine Veterinary Science, 113, 103940.
Cohen, N. D., Gibbs, P. G., & Woods, A. M. (1999). Dietary and other management factors associated with colic in horses. Journal of the American Veterinary Medical Association, 215(1), 53-60.
Ermers, C., McGilchrist, N., Fenner, K., Wilson, B., & McGreevy, P. (2023). The fibre requirements of horses and the consequences and causes of failure to meet them. Animals, 13(8), 1414.
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