There is a way that works with all versions of BIND, a way that works with Version 4.8.1 and later, and one that works with 4.9 and later.
If your name server is 4.8.3 or earlier, remove all the slave's backup zone data files (or just the ones you want to force), kill the slave server, and start up a new one.
Slave name servers will load this new data sometime within the time interval defined in the SOA record for refreshing their data.
Sometimes your users won't want to wait for the slaves to pick up the new zone data -- they'll want it available right away.
For example, you could use the eight-digit number formed by YYYYMMDD. In this form, your serial number would be 19970115.
This scheme allows only one update per day, though, and that may not be enough.