Calculating horses' energy requirements

More and more horses are becoming obese and, as with humans, overweight horses are prone to a number of debilitating conditions. So it’s important that they get the right balance of energy (calorie) intake and exercise to maintain a healthy body condition.

Estimating energy requirements and therefore how many food calories an individual horse should be fed can be challenging. The energy requirements of individual animals, even those of a similar breed and build, can vary considerably despite them being managed in a similar way and undertaking comparable levels of exercise. Understanding the factors that contribute to the energy requirements of an individual animal would help owners to decide how best to feed their horse to maintain a healthy bodyweight.

When estimations of ideal food intake are made for humans, nutritionists may take into account not just bouts of exercise, but also the level of voluntary activity (VA) in an individual. This is combination of posture maintenance, fidgeting and all other daily activities which are not classified as exercise. These can account for as much as 15% of daily energy expenditure in sedentary individuals, rising to nearly half of daily energy expenditure in certain individuals.

These are significant numbers, and if horses are similarly “voluntarily active”, that could greatly affect the energy (calorie) intake they might require.

To find out if such activity could explain even part of the variation in energy requirements, researchers from the University of the West of England and WALTHAM fitted stabled horses with movement monitors called accelerometers. These can help record just how much a horse moves when left on its own.

Twelve mature horses were selected and were paired according to their BW and breed. In each pair, however, the estimated energy intake needed to maintain a constant body weight in one animal was much lower than for its partner despite them both being managed in the same way and undertaking similar structured exercise.

Each pair was observed for 72 hours during which both structured exercise and non-structured exercise was measured. Heart rate was used as a measure of relative workload during the structured exercise.

The study found that there was no significant difference between the overall activity levels of the individual horses even if they required (and therefore had been had been fed) less energy. This suggests that differences in VA levels are unlikely to explain the difference in estimated requirements between stabled exercising horses with a similar body weight and workload. Whether VA may be important in horses that are turned out for all or part of the day however, will require further work.