Yeah, a little thin, that you can see all those ribs that clearly, that there's a 'dip' beside his tail head, but not too bad - he's by no means skinny. Looks like, by his neck & back, he hasn't got a lot of muscle, so it could also be that, rather than just 'condition' that is making his ribs so obvious. And he looks well rounded, well 'covered' over other telltale spots, such as point of hip & shoulder & scapula, although possibly different angle pics, different lighting might give a different idea.
So... a tad thin, but not worryingly so in the least - IMO he could afford a few more 'groceries'.
He's a Thoroughbred and supposed to be a bit lean and ribs seen when he breathes.
Ribs ripple under the skin when he moves...
He needs better muscle and muscling conditioning...
He's not off by much but would like to see a bit more weight on him and better muscling.
He should not resemble a Quarter Horse though in everything well covered with layers of fat.
Thoroughbreds are long and lanky in appearance and "long" muscling by breed trait not bulk and rounded of many other breeds...
Do not allow your Thoroughbred to get fat in appearance as this is so unhealthy for his body entire...
Better he look a bit lean, and I mean a bit off in weight but mostly muscling condition than rolly-polly fat.
Part of my answer depends on where you are. If you're in the northern hemisphere and going into winter, I'd like to see a bit more weight to help him stay warm. If you're in the southern hemisphere and going into summer, then he's a tad light but nothing some good groceries and riding won't cure.
Yes, I agree that it's more a matter of muscle than fat - he needs to build his muscles. Make sure that he has the proper nutrition to do that. He could perhaps need to be on a ration balancer if you don't feed a fortified grain according to the amount that it says he should be getting for his body weight on the bag. If you don't feed according to the bag directions, he isn't getting enough nutrients. Meaning that just adding more fat wouldn't help in this situation.
I've been dealing with this problem on my own horse. I put her on a ration balancer (Nutrena Empower Topline Balance) this month, in addition to the weight supplement she was already getting, and she is looking much better already.
I feel like he's just a touch leaner than I'd like to keep him, but not concerningly underweight. Many Thoroughbreds show ribs even when overweight (one of my two is like that, 75-100kg overweight currently and still shows ribs faintly under certain circumstances, and ALWAYS shows ribs when at her ideal weight), simply because of the way they're built. Well sprung ribs show easily, and a Thoroughbred should have well sprung ribs. Some are slab sided, but they aren't supposed to be.
The spring my mare nearly foundered you could still see her ribs in trot from certain angles.
Remember there is more to body scoring than ribs. One must look at the horse's muscling and at fat deposits, and at the horse's coat. Horses that are unhealthy often lack shine.
To me he looks like a case of acidic hindgut. It's super common in TBs if they are being fed grain or have been recently.
Basically, the kind of bacteria that digest hay and roughage are different from the ones that digest hay. So if a horse has been fed a lot of grain, they lose the bacteria that have the ability to digest hay. So you feed more grain and it becomes a cycle.
If you want a horse that gets nutrition from the majority of their diet, which is roughage, feed only hay, or roughages and add a probiotic to help the gut readjust.
You might consider treating for ulcers as well, and adding amino acids can help them build muscle back faster. I like tri-amino, it's very affordable.
He gets no grain, hes been on this diet for two years, he gets free choice fescue hay, 3 quart scoop of coolstance copra twice a day, 3-4 flakes of alfalfa, california trace plus minerals and vitamin e and magnesium, he has been mostly just ridden on trails cause I dont have an arena, which is why he doesnt have alot of muscle. Hes always been a super hard keeper
What is coolstance copra? I have not seen it in my area. Well not where I shop. If he is getting free choice grass hay and 3-4 flakes of alfalfa , what are you calling a flake? The bit that pulls off, about 1 -2 wide ? that is not a flake. A flake is about 3-4 inches grab between your thumb and middle finger for an average size person . Have you had his teeth checked ? TB get wavy mouth . You could add some fat to his diet, as in oils,veggy,corn,canola,olive . rice bran is also a good source of oil. Also be sure to give him psyllium to make sure he does not have sand in his gut, which can cause mal absorption as well as colic. You could also try some probiotics to help his digestion. He is a nice looking horse.
I found you this...
This is the opening sentence from the website for this product..
Cool Stance is premium quality coconut (copra) meal, made from the white part of the coconut, which is dried, baked and ground. It is totally natural and is chemical and GMO free. It is assured quality and routinely tested for Aflatoxins. https://stanceequineusa.com/products/cool-stance/
While it sounds like you're feeding him well, it seems that hind gut damage doesn't tend to get better of it's own accord. And treatment is also difficult/not reliable. So just because he's been on a good 'gut friendly' diet since you've had him, doesn't rule out hind gut ulcers or such, from his 'past life' in racing. So I'd be looking into herbal supps(no vet prods that work on hind gut), such as slippery elm, liquorice, etc, &/or a tailor made supp such as Kelato Gastro Aid, to hopefully get his hind gut healthy.
oh, you must be back east and a two string bale. I get alfalfa in 100 to 110 lb bales. Forage is the best thing for a horse to eat. You can find senior and low starch feeds made by just about any company any more. You can find top line finish, low carb low sugar feeds, not grains, LMF Purina and Nutrena plus there are many other brands out there.
I agree, the diet sounds good. If his teeth are fine I would suggest a probiotic might help. The California Trace has prebiotics that feed bacteria but sometimes different bacteria need to be introduced to help the body get more of the good kind that will help the digestion. That is where the probiotic comes in.
Also, I suggest making sure the horse has feed in his stomach just before being ridden and during trailering to prevent ulcers.