If you plan to milk the Jersey, check the contras on the flukicide you plan to use. Some flukicides cannot be given to cows whose milk will ever be drunk (by humans), some not within 60 days of calving (so you'd be fine.)
If you have reason to think they may have fluke, then (if milk for human consumption is not an issue), the usual protocol is dose on housing and again 6-8 weeks later. That way any eggs or immatures the first dose doesn't get will get wiped out by the second dose.
On the beef / lamb farm in Cumbria, we wormed youngstock on first turnout after weaning, and they got a mineral bolus then too, and fluked adults as above on housing. Other than that, no worming unless there was a problem.