Why this breed loses rather than gains
Ask what changes in an aging Thoroughbred and the honest first answer is direction: where a pony gets rounder with age, a Thoroughbred gets lighter. The breed runs on a higher base metabolism than most, bred for generations to convert feed into speed, and many individuals stay lean-burning for life. Add the wear of a racing or sport career — joints that stiffen, a back that loses muscle, old injuries that change how comfortably a horse stands at a hay net for hours — and the senior Thoroughbred spends more energy standing, shifting, and simply existing than the horse he used to be. Digestion also extracts less from each mouthful as the years pass, so a ration that held him easily at twelve can leave him short at twenty-two without anything dramatic going wrong.
A sensitive stomach behind the picky bucket
The appetite pattern in an older Thoroughbred is often selective rather than absent, and that selectivity carries information. A horse who walks away from grain but still pulls at hay, who eats eagerly one day and leaves half his bucket the next, or who grows girthy, restless, or dull around feeding time may be a horse whose stomach is uncomfortable. Gastric ulcers are a well-known problem in this breed, in race training and beyond it, and discomfort of that kind is a classic reason a Thoroughbred goes off concentrated feed while keeping some interest in forage. None of that can be confirmed from the feed room — only a vet can investigate it — but the pattern is worth recording precisely and raising at the next visit rather than masking with sweeter, richer feeds that may suit his stomach even less.
More calories without more fizz
Feeding an aging Thoroughbred up is an exercise in density without excitement. The foundation stays forage, offered as generously and as continuously as his teeth allow, because a near-constant supply of hay suits both his weight and his stomach better than long empty hours between meals. Extra calories are then better added as fat and highly digestible fibre than as larger cereal meals: big starchy buckets risk a fizzy, reactive horse and an unhappy gut, while oil-rich and fibre-based feeds build condition more quietly. Several smaller meals beat two large ones, changes should arrive gradually over days rather than overnight, and a horse who eats better turned out calmly, or fed away from a pushy field mate, is telling you that the setting is part of the ration.
Weekly proof, not monthly impressions
Monitoring an aging Thoroughbred has to run faster than monitoring most horses, because his drift is fast. A weight tape once a week, taken at the same time of day, plus a dated side-on photograph each fortnight, will catch a slide while it is still a small correction rather than a rescue. Feel for the topline as well as the ribs: a Thoroughbred can look merely lean while the muscle along his back and over his hindquarters quietly melts, and that muscle, once gone in a senior, is slow to rebuild. Weigh the hay he actually eats, not the hay he is given, since scattered and trampled forage is common with a restless eater. Call the vet sooner rather than later if the tape keeps falling despite a generous ration, if pickiness at grain becomes refusal, or if weight loss arrives with a dull coat and flat attitude. KinsLe Pet Passport holds this Thoroughbred's weekly tapes, photographs, and appetite notes as one dated run of evidence, so a vet can judge how quickly he is changing and where the slide began.