VN's are pretty easy for even day olds to use.I got some horizontal nipples and vertical ones what age should i start them on the nipples? Was told and have read from 1 week to 2 weeks other say then tey start knocking over and perching on top of their open water jars.
I don't use VN's because they leak too much, among other issues.
HN's can take longer as they are harder to activate.
I have HN's in the brooder from the get go, along with the open waterer.
Some catch on quick, others not so much.
@RoosterML has rigged one with both VN's and HN's...it has yet to be tested.
https://www.backyardchickens.com/th...ng-dry-and-clean.1290765/page-3#post-20971984