Sentence: A total of 32 PRRSV-negative pigs ( 3 wk old ) were randomly assigned from within blocks to 1 of 4 treatments in a 2 by 2 factorial arrangement ( 2 types of diet : control ( 0 % ) and ACT addition ( 0.04 % ) ; and with and without PRRSV ) in a randomized complete block design. 
 Section: finding