You have a manger "on demand" for the hens?
We have automatic feeders for chickens and other poultry that maintain the level of food as they are equipped with tank.
I can recommend the following models:
FEEDING FOR HENS AT FOOD
POWER SUPPLY FOR POULTRY WITH ROOF Prissy
For the need to provide food only for the hens at particular times, we can not offer solutions, you should find your way to a manger with timer or with some electronic or mechanical detection of presence and Processor Open.