Salt: the one mineral he actively craves
Sodium is the gap in almost every forage-based diet. Grass and hay are low in salt, plain cereals add little, and yet a horse loses sodium every day in sweat, urine and droppings — far more of it when he is in regular work or the weather turns hot. Horses are unusual among farm animals in having a genuine, specific appetite for salt: given free access, most will take roughly what they need, visiting the lick little and often rather than gorging. That makes salt the one supplement you do not measure into the feed by default. You provide it, keep it available, and let the horse's own appetite do the dosing.
Loose salt versus the hard block
The familiar coloured block was designed around cattle, whose rough tongues can work a hard surface all day. A horse's tongue is smooth by comparison, and some horses simply cannot lick fast enough to satisfy a real sodium hunger from a block, particularly after hard work. Loose salt in a small tub or a salt holder gets round the problem — the horse can take a mouthful in seconds — and many owners find a plain white block is ignored while a tub of loose salt empties steadily. Whichever form you choose, site it under shelter near the water supply: rain dissolves an outdoor block into a salty puddle and then a memory, and a horse who has just taken salt needs to drink, so the trough and the lick belong within the same short walk.
Mineral licks: useful, with homework attached
A trace-mineral lick is a different proposition from plain salt, and the honest answer is that it depends on the rest of the diet. If your horse eats a fortified compound feed or a balancer at anything like the recommended amount, he is already receiving a considered spread of minerals and vitamins, and a mineral block mostly duplicates it — harmless in many cases, but not filling a gap. For a horse living on forage alone, a horse-specific mineral lick or loose mineral can contribute something real. Read the label either way, choose a product made for horses rather than for cattle or sheep, and be wary of stacking several mineral sources at once; more is not automatically better with trace elements.
The lick as a daily observation point
A salt lick earns its keep as an early-warning post. A horse who suddenly empties the tub, chews the holder, or starts licking soil and fences is telling you something about his diet or his workload that deserves a look, while a lick that vanishes in a rainstorm and is never replaced leaves the whole yard unsupplemented without anyone noticing. Glance at it daily: present, dry, clean of bedding and droppings, and roughly the size it was last week. Because it is a thirty-second job that everyone assumes someone else has done, it is exactly the kind of check KinsLe's Care Teams turns into a named, timestamped duty in your horse's routine — seen to every day, and provably seen to.