Feeding the Thoroughbred

To love thoroughbreds is to love the absurd. Thoroughbreds are not your average horse or backyard pony. They are highly specialized performance athletes, carefully bred over the past thousand years to be good at what they do: running. 

Just like highly specialized dog breeds such as Aussies, German Shepherds, and even sporting retrievers like Labs and Goldens, thoroughbreds are built for a specific job. That job requires a lot of energetic resources, aka calories, expendable and easily available energy. Not all thoroughbreds are going to love or be good at the job they were bred for, just like that Golden Retriever you bought to hunt birds with may not get the point and might prefer that couch-potato lifestyle. That doesn't mean though that their body isn't still wired to function in a certain way. 

Just because my horse, Smoky, prefers the life of leisure over running doesn't mean his metabolism will function differently. It's still going to have a high caloric demand and be efficient at turning those calories into energy. And that's where I've found people struggle the most at managing thoroughbred's diets. 

There are two foundational elements of knowledge about the horse's digestion that will help set the ground work for keeping thoroughbreds healthy and happy and sitting at a 5 or 6 on the Body Condition Score:

1. Horses are meant to graze nearly all day long to meet their energy requirements. Their skeleton and musculature support the movement of grazing, and the presence of forage in their gut supports energy production and prevents ulcers.

2. Cheap energy is cheap energy. We know what a sugar crash looks like in toddlers and adults, we know what it's like to get hangry, and for a 1300lb animal, presumably without cognition, that can get pretty ugly.

Here's a great study on how this all works and why it matters

So what's cheap energy vs high quality energy and why does it matter? Well, for that we have to get into the science of it. We know horses need at minimum 1.5% of their body weight in forage every day. But what exactly is forage? For horses, it's grass and hay, and can include other things like beet pulp or legume hulls. And what those essentially boil down to is fiber. Fiber is a component of carbohydrate that is not as easily broken down and digested as starch, aka sugar. For horses, that fiber actually is digested in the hind-gut, the lower portion of the intestinal tract, where through fermentation it is converted into volatile fatty acids which are the primary source of energy.

Starches and sugars that are not fully digested and processed before making it to the hind-gut can actually result in a lowering of the pH in the hind-gut and lead to gastrointestinal disturbances like ulcers and bacterial imbalances. 

So why does any of this matter? Can't you just give the horse a bunch of hay and some pelleted feed and call it a day? You could, but then you'd be in the position I'm in with the new barn Smoky is at. We won't get into the details of what was promised and agreed to and how it's turned out, but we will get into what was working, what isn't working, and why.

Before I moved Smoky, he looked like this:

He's about a 6-7 on the body condition score, and he was very happy. He was calm, had plenty of energy for rides, and had a relaxed, easy going manner. When grooming, he wasn't twitchy or reactive. Here he was getting 2 scoops (the big blue ones) of Triple Crown Senior and 2 scoops of alfalfa pellets twice a day, in addition to plenty of grass and all the hay he wanted if he was inside due to the weather or through winter. This picture was taken in summer, but he looked the same in October 2024 right before I moved him. 

This picture was taken in May 2025, just the other day:

You can see that he now sits at about a 3 on the body condition score (don't worry, we're moving barns). There is significant weight loss in just 6 months. Currently he's getting 2 scoops of Tribute Performance Advantage, 1 scoop of a soaked alfalfa pellet/beet pulp mix, and 1/2 scoop of Tribute Essential K. Through winter he was getting free choice hay, but currently he is not, he only has poor pasture available. For about a month it was almost entirely buttercups. He is not happy, very preoccupied with eating when we are out, he is lacking energy under saddle, and he is twitchy and uncomfortable while being groomed. 

There are no real differences in his exercise, in fact he's getting less work now than he was last summer. His current pasture is a little smaller but not by much. The soaked beet pulp and alfalfa may actually be less than he was getting before since we did not soak his alfalfa at the last barn. There is a big difference in the availability of grass, and there are some differences in the feeds that I'm going to show as well.

This chart shows a rough breakdown of the percentages of fat, protein, starch, and fiber in the feeds he's getting. 

On average we can assume he's getting these percentages at every feeding, but again this may not be wholly accurate because they are scooping soaked alfalfa and beet pulp.

I see a couple big differences here. Fat and fiber are much higher at the old barn. Sugar is much higher at the new barn. 

With what we've just learned, we can follow this rationale to figure out what the real issue is. With less fiber he is getting less sustainable and naturally bio-available energy, meaning he has to turn to other energy sources to supplement it. Since he's not getting as much fat, that secondary energy source could be sugar, but we know sugar is typically burned quickly after consumption, therefore his body has turned to using his own muscle and fat as energy, hence the weight loss. We can also probably assume that the additional sugar without the same amount of roughage available has thrown off his gut biome, and he may indeed have some ulceration in his stomach. 

And please note, we are only looking at the pelleted feed he's been getting. This is not fully taking into consideration the hay or grass quality, though as I mentioned, he did have free-choice hay through winter, and it's only May. I noticed weight loss in January and February, not entirely unusual for Smoky, but it only progressed. I had hoped it would resolve itself when the grass came in, assuming they were going to continue getting free choice hay, but they stopped getting free choice hay before the grass even came in. 

So what are the lessons here? Roughage should always be the foundation of a horse's diet, that is grass and hay. They need free choice access to consume as much as they want. When adding pelleted feeds, making the priority fat and fiber will provide the horse with the energy and calories he needs to maintain a healthy weight and balanced energy, while also ensuring proper digestion and gut biome balance.

If you're looking to improve your thoroughbred's body condition, consider a senior feed like Triple Crown Senior with alfalfa pellets (soaked or dry depending on your horse's tolerance) in addition to free choice hay. This is not a sponsored post, just a really great example of what not to do when it comes to feeding thoroughbreds.

And yeah, I'm not happy about his current body condition. What's even worse is that the other thoroughbreds on property look worse than Smoky does! We are moving to a new barn soon that should hopefully resolve this weight loss through adequate forage and a more customized feeding plan. I'll try to provide an update in a month or two on how that's going and if Smoky's condition improves.