Effect of Two Doses of Different Zinc Sources (Inorganic vs. Chelated form) on the Epithelial Proliferative Activity and the Apoptotic Index of Intestinal Mucosa of Early-weaned Pigs Orally Challenged with E. coli K88

The effect of two doses of different sources of zinc, inorganic (zinc oxide) or chelated (zinc glutamate chelate), on morphology and turn-over of the small intestine was assessed in early-weaned pigs orally challenged with enterotoxigenic E. coli K88 (ETEC). Sixty pigs weaned at 21 days were assigned to one of the following 5 diets: control (C); C+Zinc oxide (ZnO), either a 200 or a 2,500 mg Zn/kg dose; or C+zinc chelate with glutamic acid (Glu-Zn), either a 200 or a 2,500 mg Zn/kg dose. On d 2, the pigs were orally inoculated with 1.5 ml of a $10^{10}$ CFU/ml E. coli K88ac O148 suspension. Zinc supplements did not improve the performance of the pigs, but on d 5 faecal excretion of ETEC was reduced, and this was mainly due to high zinc doses (p<0.05). The villous height in the duodenum was improved by the zinc supplements (p<0.01) whatever the source and the level, whereas no effect was seen in the other two tracts of small intestine. The diet did not affect apoptosis and mitosis counts, while ETEC-susceptible pigs had more mitotic cells in the villi than non-susceptible pigs, particularly in the jejunum (p<0.01). The duodenum had fewer mitotic cells in the villi (p<0.05) and in the crypts (p<0.01) and more apoptotic cells in the villi. High dietary doses of ZnO or Zn-Glutamate improve villous height of the duodenum, but not of the jejunum and the ileum, and do not affect the epithelial proliferative activity and apoptotic index of intestinal mucosa of early-weaned pigs orally challenged with ETEC.