Why does named log the warning message "no TTL specified - using SOA MINTTL instead"?
Your zone file is illegal according to RFC1035. It must either have a line like:
at the beginning, or the first record in it must have a TTL field, like the "84600" in this example:
example.com. 86400 IN SOA ns hostmaster ( 1 3600 1800 1814400 3600 )