In earlier days, males and females were fed in the same feeding systems. As males eat much faster, have a greater appetite and actually need less feed then females, they often became to heavy, with a negative influence on fertilty and hatchability.

In the late '70s, a system was developed, based on earlier work done in France with dwarf breeds, that separated males and females by the size of their head and the height of the bird.

On the female feeder, a grill was placed which had an opening that was too small for the male to eat. The male feeder was placed so high that the smaller female couldnt reach it. In this way, a much better control of bodyweight was obtained. As a result, an increase in fertility of approximately 3-5% was observed, especially in the second part of the production period.

Later research showed that:
- The grill size must focus on the size of the females. For most breeds, a grill size with a minimum opening of 44 x 70 is required.
Having the female grill so small that the smallest male but also the biggest female was excluded can give severe drops in production.
- Not all systems are equally effective.
Some systems are bending severly, leading to a big variation in opening for the males, which makes it less effective.
- Body weights must be observed carefully, especially early in production
Small and young males can still eat with females, but will be excluded and with that restricted as they grow bigger. This can have a very negative effect on them, as they will stop growing
- Behaviour had as much influence as body weight
Especially the male behaviour is influenced by the system. This is as much responsible for the increase in fertility as the male body weight.