Just as it is for humans, obesity is harmful for horses, too. Not only does exercise demand greater effort, the extra fat actually worsens the animals’ performance on a chemical level.
According to a Swedish and Icelandic study including nine Icelandic horses, an increase in body fat in horses leads to negative changes in blood levels during and after exercise. Even a weight gain of as little as 45 lbs is enough to affect the horses’ blood chemistry.
The study found that lactate breakdown, glucose availability and the relative proportion of red blood cells in the blood had decreased. A decrease in the proportion of red blood cells associated with an increase in body fat percentage has never been seen in any other species before. These factors cause horses with a higher body fat percentage to take longer to reach their normal respiratory rate after exercise and it also limits their performance.
Heavier horses get a crooked posture
Weight gain also has a negative impact on the horses’ locomotor system. Especially in the forehand and after training, the asymmetry in their movements increases. This led the scientists to the conclusion that acute loading combined with weight gain is additionally detrimental to the movement.
The reason for the change in the locomotor system remains to be unclear. However, human research has shown that weight loss can reduce pain and obesity can alter the biomechanics of walking. In addition, the production of neurotransmitters related to inflammatory processes in the body increases as older horses gain weight.
Owners are often unaware of their horses’ excess weight
In their paper, the researchers state, “(Our) results clearly show that a 5% to 8% increase in body fat percentage, body weight and body condition lowers physiological and metabolic fitness … and impairs actual performance.” A major problem, however, is that horse owners are often unaware that their animal is suffering from obesity, Johnsson said. Often, excess weight is mistaken for muscle mass, he says.
Johnsson therefore urges horse owners to educate themselves about the animals’ body conditions and also learn how to keep their recreational and sport horses in moderate body condition. This, he says, is important to support the horses’ performance and health.