Gonna be a little upsetting! It really all depends! For both your worming and vaccination program, I truly believe you should consult your vet.
I know that our protocols have changed on that here in NC. We've moved the ages back (older) for the 1st and subsequent vaccinations (starting @ 5-6 months instead of 3-4 months). Our worming program generally starts with Panacur at 30 days of age, then at 60 days Strongid (single dose) then then rotating until 6 months old. The 6 months old worming is done with Ivermectin put in the rotation, then continue rotating the 3 until 1 yr of age. Then the yearling joins the regular rotation with our mature ponies as long as they are doing ok.
This doesn't seem to work as well since moving to this property - when we've done fecals - both before AND after worming - egg counts have been high... And some of those LOOK GREAT while others have looked not "thrifty". Along with dealing with the lice here, we've been doing LOTS of extra power pac (panacur - double dose/5 days) - especially on the youngsters between 8-18 months of age. Then they look good...
BUT now I'm looking at doing things differently - started by switching most of the ponies over to field oats for eating and this worked well (so far) w/ everyone EXCEPT the 4 broodmares with foals. Due to what our feed stores carry in our area (easily accessible - 2 different TSC's & 1 main feed store), I had started them on a broodmare feed (only purchased the 2 bags the feed store had - didn't like it) and then yesterday went back to Nutrena Safe Choice Original (pellets), adding Mare Plus for a supplement. Have started adding ACV to their feed (for overall health, not worming) and looking at trying a remedy that has been used on cattle safely (& supposedly on horses, but I haven't found where it's actually been done??). That is to use a cup of Shakley Basic H (soap) in 100 gallon tank of water. Haven't tried it yet, still studying that one...
And again on weaning - I've weaned as early as 2 days (first Shetland foal's dam wouldn't accept her - raised like an orphan for 20 days - going back/forth to daycare w/ my children in the front of our trk - long story - should be here on these pages somewhere), 2 months of age (that was a special case where our well adjusted, good eating Shetland filly went to another barn to "show" a Spotted Saddle Horse orphan filly "how to live") and as late as 1 yr of age.
I've had weaned yearlings & two yr olds go out and nurse back on their dams the following foaling season & had one mare that 2 yrs in a row would have 6 youngsters lined up (3 on a side) and they'd take turns nursing - her current yr foal, another suckling, her yearling, 2 other yearlings, another 2 yr old. I always only saw that on the days I didn't have a camera with me, so never got pics! I swear "Sioux" smirked at me on those days. She did eat a lot of feed (and looked GREAT) AND the current yr foals were eating well at the time.
If your current foal is eating well and looks good, I'd say start to wean by first taking the colt out on "walk-a-bouts" and/or trailer rides w/o his dam. Then take his dam away while working her (if you are?). We usually set up a nursery as our riding lesson pony mares were "working" for several hours at a time. The foals went into one pen - with free choice hay/feed/salt and water. They watched their dams but rarely called out or got too excited.
More later - have to run..
