Each of the connected groups of fence can be separated into a series of letters in the pigpen cipher, with pigs acting as dots. In reading order, these are:
Using the standard pigpen cipher, this translates to ACCORDING TO ADAGE, WHAT SPORT SHOULD YOU AVOID DOING WITH PIGS? (THREE NINE). The numbers given at the end are the length of the words in the answer. The clue phrase refers to a frequently quoted saying, variously attributed to many people, along the lines of “Never wrestle with a pig – you both get dirty and the pig enjoys it.” The answer is MUD WRESTLING.