Commercial layers are bred to produce the greatest number of eggs and broodiness is undesirable. The tendency to brood has been eliminated in them by selective breeding over the generations and broodiness is rather rare, but less usual hybrid combinations or “colours” become broody more often.
The tendency to brood or underdeveloped maternal instincts are a breed characteristic - for instance in traditional breeds, particularly heavier or miniature breeds, these natural reflexes have been preserved and the hens become broody more often to very often. After laying a specific number of eggs, the hen endeavors to sit on the nest - start brooding (the sounds it makes change to a typical “cluck-cluck”, it sits on the eggs for the incubation period (21 days) and subsequently cares for the hatched chicks for about a month.
If broodiness in your hens is undesirable (and this is nearly always - unless we want to hatch our own chicks), we must not give the hen the opportunity to sit on the eggs from the outset - most importantly, there must be no nest with eggs available. It is best to separate the hen from the flock, place it in an airy cage (de-brooding cage), we recommend you hang it in the “air”, this means that the hen has no peace for sitting and gets cold (broody hens have an elevated body temperature), reduce the amount of feed you provide for several days.
Hormonal products can also be used to prevent brooding - but we usually do not want to do this in small-flock conditions.