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AskHQ: Nutritional issues OTTB

Q: What nutritional issues should I be aware of in my new OTTB?

A: Australian nutritionist Dr Nerida Richards, the resident nutritionist at, explains that a Thoroughbred who is adapted to processing 8kg or more of concentrates a day as a racehorse may have have the following problems when he comes off the track:

  • Bacterial imbalance in the hindgut: The horse’s hindgut contains two main families of bacteria, those that ferment fibre and those that ferment starch and sugars. When a high-concentrate diet is fed, the starch or sugar bacteria may start to predominate. These bacteria create a more acidic gut environment, causing a condition known as hindgut acidosis. At this pH level, the fibre-fermenting bacteria cannot function well and they start to die off. So even if your OTTB eats up his hay or lucerne, he might not be able to get much goodness out of it. Every horse is different. Some have a greater ability to digest starches than others, but any horse on a high-concentrate diet will be at risk for developing acidosis, and even horses with subclinical acidosis have a greater risk of colic as well as laminitis.
  • Gastric ulcers: It’s estimated that up to 90% of racehorses in training have ulcers. “Gastric ulcers cause many problems, but perhaps the two most relevant in the situation of feeding an OTTB are loss of appetite and weight loss,” says Richards.
  • Hoof problems: OTTBs sometimes have shelly, weak, slow-growing hooves. Richards believes that a lack of biotin is the major cause, because the imbalance of bacteria in the hindgut causes them to become biotin-deficient. Biotin can be bought as a supplement to help your horse’s hooves to regenerate with better quality.
  • Poor appetite: This can be due to gastric ulcers, or a vitamin B1 deficiency caused by the high-concentrate diet.

“The first critical step in getting a Thoroughbred back to normal is to restore the balance of bacteria in the hindgut, and get fibre digestion working properly again,” Richards says. Concentrates can be tapered off over a couple of months. However long it takes, your aim should be to switch the horse to a low-concentrate, high forage diet.

This can include:

  • Ad-lib good-quality hay.
  • Lucerne (4-5kg/day if needed for the first couple of months, cutting down to about 2kg/day long-term).
  • Feed balancer or a vitamin-mineral supplement (fed in recommended quantities).
  • Brewer’s yeast (up to 80g/day assists with hindgut health and fibre-digestion).
  • Biotin (20g/day assists with hoof health).
  • Vitamin B complex (10g/day for picky eaters).
  • High-fibre and high-oil alternatives such as beet pulp, copra, linseed oil, canola oil or crushed linseed can be phased into the diet if necessary.
  • Little or no concentrates ultimately – if any concentrates are fed ultimately, you should choose low-starch ‘leisure’ concentrates rather than ‘performance’ concentrates.

NOTE: Seek the advice of your vet or equine nutritionist to get the specific recommendations for your horse.