Having dealt with exotic, problematic rats ever since the horrible 2004 hurricane season, I can tell you that your pigs display the EXACT reaction to rat poison - its a very long, agonizing death actually - usually takes 3 days, and is the main reason I stopped using rat poison, that and accidental poisoning of other critters.
Rat traps work MUCH better, and besides not poisoning critters you don't intend to, you do not have rats dieing in horrible places - such as your roof - and stinking up your home.
Rat poison is mainly arsenic, and its a long, painful death.