Digestible energy content of the diet, also referred to as the calorie content, is in my opinion, one of the most overlooked aspects of equine nutrition. Many horse owners will focus in on the protein percentage of their feed, or the sugar content of the hay, however, calories are rarely discussed.
Adequate weight management is one of the most common goals that horse owners come to me with, especially in the winter months. If you have a hard keeper that struggles to maintain weight, this issue is normally exemplified by lack of pasture access and lower temperatures.
On the other hand, owners with easy keepers tend to struggle with maintaining their horse in an adequate condition year-round. In the summer months pasture access poses an issue, and in the winter months there is normally less opportunity to exercise their horse.
When you think about balanced nutrition, oftentimes, adequate nutrients such as crude protein, or calcium, come to mind. But managing a horse in a healthy body condition truly boils down to calorie content of the diet. So, let’s dive into calories for horses, how much your horse needs, and understanding how to optimally supply them!
As always, let’s start with the hay. In almost every equine diet, forage, and in Ontario most frequently hay, is the primary source of calories. The calorie content can vary significantly in hay. If we look at hay harvested in Ontario in the year of 2023 that was analyzed by Balanced Bay, the average calorie content was 2 Mcal/kg, the lowest was 1.5 Mcal/kg and the highest was 2.6 Mcal/kg. This is a huge range! However, these numbers won’t mean anything to you if you do not know how many calories your horse requires daily.
A 500 kg easy keeper that is not in work requires 15.2 Mcal/day. If this horse is consuming 2% of their body weight in hay daily the low energy hay (1.5 Mcal/kg) would be meeting their required calorie intake, and it is unlikely that you would even have to restrict their intake!
It drives me crazy when horse owners assume that just because a horse is an easy keeper means that they need their hay restricted to an intake of 1.5% of their body weight daily. If you have low energy hay, you may not need that level of forage restriction. On the other hand, if you are supplying your easy keeper with hay that is high energy (e.g., 2.6 Mcal/kg) you will not be able to safely restrict their forage and elicit weight loss as even an intake of 1.5% of their body weight would be over supplying calories.
On the other hand, if you have a horse that is a harder keeper, or you have a horse that is an average keeper but is in a moderate-heavy workload it is preferable to have hay that is higher in calories. A 500 kg horse in heavy exercise will require about 26.6 Mcal/day. If you have the high calorie hay that is 2.6 Mcal/kg, this horse will not require significant supplemental concentrates as the forage is meeting their requirements. When the hay is low calorie, you end up spending a significant amount of money on supplemental concentrates and you may be compromising gut health as the horse needs to consume a large amount of concentrate to maintain their weight.
When wanting to alter your horse’s body condition, and elicit either weight gain or loss, evaluating the calorie content of their diet is critical. To maintain a horse’s weight, they should be at a net zero energy balance. This means that the calories provided to the horse matches their daily calorie expenditure. A positive energy balance is required for weight gain, meaning that the diet provides more calories than are spent, and a negative energy balance is required for weight loss. This is when the horse is using more calories per day than are supplied in their diet.
When you work with an equine nutritionist on a continual basis and feed your horse analyzed hay, you are able to have optimized management as your nutritionist will be able to keep the overall calorie content of their program stable as to avoid unwanted weight gain/loss.
For example, if you have a light riding horse that has been maintaining their weight well on free choice access to hay that has an average calorie content of 2 Mcal/kg, but then the 2025 hay tests at 1.5 Mcal/kg, we can get ahead of the impending weight loss by adding supplemental calories. This could be done with a fortified concentrate, an oil, or a digestible fibre source such as beet pulp.
The type of calories to add for your horse is also a key consideration. For example, if you have a metabolic light riding horse that needs additional calories, opting for a fat source is likely the best option for that animal. However, if you have an elite performance horse incorporating some hydrolysable carbohydrates may be recommended to support their performance and energy levels.
To conclude, the calorie content of equine diets is rarely discussed, but critical to managing our horses in a healthy body condition. Working with an equine nutritionist to understand your horse’s calorie requirements and ensure continual optimized nutrition is the gold standard. Stay tuned for next month’s article on types of calories, and choosing the best calorie source for your horse’s unique needs.
By: Madeline Boast, MSc. Equine Nutrition