Commercial hatcheries use them. I can't remember exactly what the difference is in nutrients, whether it is minerals of vitamins. I don't recall seeing them at the local feed store but I don't look that hard for them anyway. I don't use them and get pretty good fertility. Mine do forage for some of their food so maybe that helps.
@Adam Belcher some breeds that have fluffy feathers (like Cochin) need the feathers trimmed around the vents so the rooster can hit the target. That's trimming both males and females.
At 10 months I'd assume the pullets have been laying for a while so it should not be start-up issues with new layers.
I envision a breeding trio so no issues with number of pullets per cockerel. I assume they are mating.
Just out of curiosity what is your fertility rate? Are you measuring that by looking for the bulls eye?
