Pigs Self Vaccinate ?

I am not posting this article to bring up more criticism of CAFOs' . Note the statement near the articles last paragraph that states pastured sows will sometimes cannibalize their dead piglets as a means to vaccinate themselves against the disease which killed their offspring :

http://www.npr.org/blogs/thesalt/2014/02/20/280183550/piglet-smoothie-fed-to-sows-to-prevent-disease-activists-outraged

Mother Nature knows best !