Yes — but the leaf decides the value
Chickens can eat lettuce, and a flock let loose on a bolted lettuce bed will reduce it to stems in short order. What lettuce gives them depends heavily on the leaf in question. Lettuce is not one food: the pale, crunchy hearts and the deep green outer leaves of the same plant sit at opposite ends of the nutritional scale, and the treat rules change with them.
Iceberg and the water problem
Iceberg and crisphead lettuces are mostly water held in a crisp structure, with very little fibre, protein or vitamin content behind the crunch. Hens enjoy them, especially on a hot day when the cool leaves double as hydration, but a flock that gorges on iceberg is filling crops with flavoured water. The predictable result is a day of loose, watery droppings and hens who ate a great deal while taking in very little. Small handfuls, a couple of times a week, keep iceberg in its proper place as refreshment rather than feed.
Darker leaves earn their keep
Romaine, cos, butterhead and loose-leaf varieties carry more of what a hen can use: vitamin A and folate in the green pigment, more fibre, and a texture that tears satisfyingly. The outer leaves you strip off for the family's salad bowl — too coarse, too dark, slightly tough — are exactly the part worth sending to the run. Gardeners should note that a lettuce gone to seed turns bitter as it bolts; hens will still eat it, in smaller amounts, and the bitterness does them no harm, though the milky sap from a cut stem puts most birds off the stalk itself.
Serving lettuce well
Wash leaves from the shop, and any garden leaves that have grown near slug pellets or sprays should go to the compost, never the run — lettuce should only come from ground you know is chemical-free. Shred or tear large leaves: a whole leaf gets dragged through the dirt, stood on and abandoned, while strips get eaten. Scatter the shreds widely so shy hens get their share away from the flock's bold first rank. Serve lettuce fresh; a slimy, blackening leaf from the bottom of the fridge is not a treat, it is a stomach upset in waiting, and uneaten lettuce should be cleared away the same day before it wilts into the bedding. Unlike cabbage, lettuce wilts too fast to be worth hanging up — this is the one green that is always better scattered fresh than suspended.
Lettuce in the bigger picture
Treat lettuce as the flock's salad course: light, green and occasional, sitting alongside the layer feed that actually builds eggs. It pairs naturally with the heavier treats — a shredded lettuce base makes a small amount of cheese, corn or mealworms spread across more beaks. Because it is so easy to overdo from a glut of garden thinnings, it helps to decide in advance whose job the greens are.
The rota in KinsLe's Care Teams does exactly that, so the flock's lettuce arrives as a planned course rather than every gardener's daily dump of trimmings.