Dealing with obesity in horses

Dear Prof McCrindle,

I recently bought a 13-year-Ȳold, 16hh Thoroughbred mare that has never foaled. Despite being exercised four times a week, she is significantly overweight. What should I be feeding her? Are there any supplements that she needs? She seems to be hungry all the time.

At the moment, she is given three meals a day, each of about 2kg of concentrate/feed (Epol Rider Muesli). She also receives lucerne ad lib.

Kind regards,

Pamela

Dear Pamela,

Your mare’s obesity could stem from lack of exercise if she is otherwise healthy. Modern Thoroughbreds are very good doers, and many retired broodmares on pasture are fat and shiny.

If your horse is not lame, consider exercising her regularly on the lunge. Slow down to a walk if she starts puffing and panting, then move up to a bit of trotting, and slow again to a walk. Start with 10 minutes of trotting in each direction until you build up her muscles; this should take two to three weeks. She can then start doing a few circles at a canter and back to a walk and trot to build her muscles and get her fit.

There are several other reasons a mare would be overweight. One is pregnancy.

It is now breeding season; is she perhaps coming into season? If not, have your veterinarian check her and estimate a foaling date. At the same time, ask for a full physical examination and blood tests.

Heart failure is one of the consequences of obesity in horses, as it is in humans, so if your vet hears an increase or irregularity in her heart rate, an electrocardiograph is needed.

Ask your vet or equine physiotherapist for advice on an appropriate weight loss and exercise programme to improve your horse’s cardiac fitness. You could also discuss with him or her a change of diet to improve weight loss and fitness.

Six kilograms of feed a day and lucerne ad lib is likely to be too much if the horse is not being ridden for at least two hours a day. I would halve her concentrate and feed her only 3kg of lucerne a day.

Equine metabolic syndrome is also a cause of obesity, although it is seen more often in ponies and draught horses. Besides being very lazy and obese, an affected horse loses muscle mass and is prone to laminitis. It also typically shows increased fatty deposits along the crest, over the ribs and above the root of the tail. The cause is dysregulation of insulin, which is produced in the pancreas.

Cushing’s disease, otherwise known as pituitary pars intermedia dysfunction, is yet another metabolic disease that results in obesity in horses.

Both conditions are diagnosed using blood tests and can be managed by diet. Kind regards,

Prof Cheryl McCrindle

ȊȲSource: Pratt-Phillips S and Munjizun A. 2023. ‘Impacts of Adiposity on Exercise Performance in Horses’. National Library of Medicine – Animals 2023, 13(4), 666. bit.ly/419MzRs.