I put 9 pig spawners around grass, changed the worldborder so all the spawners were outside the border then watched as the pigs spawned, then died... repeat.
Environment
System.getProperty('os.name') == 'Mac OS X'
System.getProperty('os.version') == '10.9.4'
System.getProperty('os.arch') == 'x86_64'
System.getProperty('java.version') == '1.6.0_65'
System.getProperty('java.vendor') == 'Apple Inc.'
System.getProperty('sun.arch.data.model') == '64'
Please do NOT select Future Version - 1.8 as affected version as this is not the correct snapshot version (MOJANG is just using this version to say, for example when a issue is fixed 😉 ).
The correct version would be probably 14w29b 😉