STX2 and malabsorption syndrome: ↓ diarrhea occurrence in 1000 and 2000 mg/kg Zn; risk of diarrhea decreased ZnNPS A > ZnNPC C > ZnO; E. coli virulence genes STa, STb, Stx2, F4, F18 have occurred randomly but dramatically decreased at day 5 in treated groups (highest occurrence in ZnNPs A, lowest occurence in ZnNPs C and ZnO); ↑ level of GPx in ZnNPs A compared to other groups and CTRL; no differences in MDA levels were observed among all groups; ZnNPs A showed chronic enteritis with plaque focal atrophy and malabsorption syndrome; ZnNPs C showed mild inflammatory changes and higher expression of goblet cells