When the calf needs it and when you think (or your vet) think it's necessary. You can worm a calf at pretty well any age, just make sure you're using the correct dose and read the label to the dewormer you're using.
This depends on when you first put the calf on the bottle. But mainly, it'll be a few months that a calf goes from being dependent on the bottle to being fed as a feeder calf.
Do you want a bottle of tequila with a worm in it?
No, I have never encountered a worm in a bottle of alcohol.
No, I have never encountered a worm in a bottle of liquor.
No, I have never found a worm in a mezcal bottle.
No, I have never found a worm in a tequila bottle.
The brand of tequila that includes a worm in its bottle is Mezcal.
The brand of tequila that includes a worm in the bottle is Mezcal.
The brand of tequila that includes the worm in the bottle is Mezcal.
No, I have never dared to drink the worm at the bottom of a bottle.
No, I have never dared to eat the worm in a bottle of tequila.
No, I have never tried drinking the worm in a bottle of tequila.