The short answer for an adult Leghorn
An adult Leghorn needs layer feed available from morning let-out to evening roost, not served meals. A Leghorn is a lean, alert, white-feathered layer who eats in many small visits to the feeder, ranges restlessly for insects and seeds in between, and converts feed mainly into eggs rather than body weight. Limiting her to two feeding times works against that pattern, leaving her crop half empty through the most active part of the day. Your two anchor moments are opening the feeder and checking it at let-out, then topping up and counting birds in before the pop-hole closes.
Little and often suits the Leghorn frame
A Leghorn's size explains her meal pattern better than any timetable does. She carries almost no spare flesh, flies and scratches with an energy heavier hens do not match, and in lay she is forming an egg on most days, so her crop empties quickly and she returns to the feeder in short bouts all day long. Treats and scraps scattered as entertainment are eaten eagerly by Leghorns precisely because they are always ready to eat, which is why those extras should stay small compared with the layer ration she takes from the feeder. A Leghorn who cannot reach feed for long stretches because a feeder ran empty by midday will still forage, but the balanced part of her diet is what ran out.
Running the Leghorn pen through the day
Hang or set the feeder where the flock shelters in bad weather, raised so Leghorns do not scratch bedding through the ration, and keep it filled in the morning rather than rationing by the handful. Put water where it stays clean through the day, and offer insoluble grit and a shell source in separate small pots that laying Leghorns visit on their own schedule. If you scatter a small afternoon handful of feed on dry ground, do it away from the feeder so the whole flock gets a foraging bout without a scrum at one point. Before roosting, a Leghorn naturally takes a last good feed, so an evening check that the feeder is not empty matters more for her than an elaborate morning routine.
When a Leghorn goes off the feeder
Because a Leghorn is normally first to any food, a bird who ignores the morning feeder check while flockmates feed is a bird to catch and examine. Pale comb, a pause in laying together with reduced eating, or a hen standing hunched and apart in the run all justify prompt advice from a veterinarian, since layers can go downhill quickly once intake drops. Also check the practical causes first: a feeder jammed or emptied early, a bully hen guarding the only feeding point, or water frozen or fouled so she cannot drink with her feed. In a mixed pen, watch that bigger breeds are not finishing the ration while the lighter Leghorns wait. For households sharing chicken chores, KinsLe Care Teams lists the Leghorn feeder fill, grit pot, and evening count-in as separate assigned tasks, each stamped when the helper finishes.