PSII-16 Comparison of Microencapsulated Zinc Oxide and Conventional Zinc Oxide on Weanling Pig Small Intestinal Morphology

Abstract

Abstract A total of 300 pigs (DNA 200 × 400; initially 6.04 ± 0.08 kg BW) were weaned at an average of 21 d of age and used in a 42-d experiment with 12 replications per treatment. At weaning (experiment d 0), pigs were randomly allotted to one of five dietary treatments: 1) negative control (standard nursery diet containing 110 ppm Zn from trace mineral premix); 2) control diet with 3,000 ppm added Zn in the form of ZnO in phase 1 and 2,000 ppm added Zn in the form of ZnO in phase 2 (High-ZnO); 3) control diet with 400 ppm added Zn in the form of ZnO in phases 1 and 2 (Low-ZnO); 3) 3,000 ppm added Zn in the form of microencapsulated ZnO in phase 1 and 2,000 ppm added Zn in the form of microencapsulated ZnO in phase 2 (High-MZnO); 5) 400 ppm added Zn in the form of microencapsulated ZnO in phases 1 and 2 (Low-MZnO). Pigs were fed dietary treatments from d 0 to 28. On d 28, a subset of pigs with a BW closest to the treatment mean (n = 30 total; 6 per treatment) were euthanized via captive bolt and necropsied for collection of small intestinal tissue to evaluate morphology at the Kansas State University Veterinary Diagnostic Laboratory. Briefly, after pigs were slaughtered, they were opened viscerally, and the small intestine was identified. Two samples (approximately 2 cm long) were cut from the proximal and distal ends of the ileum and fixed in formalin. Samples were then embedded in paraffin and 4 µm cross-sections were cut and stained with hematoxylin and eosin. Slides were analyzed using a microscope at 10× magnification. Measurements [villus height (VH), crypt depth (CD), and villus height:crypt depth ration (VH:CD)] were evaluated from 10 unbroken villi and their corresponding crypts. Data were analyzed using the GLIMMIX procedure of SAS (version 9.4) with individual pig as the experimental unit. No evidence of differences in proximal ileal VH (P = 0.34), proximal ileal CD (P = 0.52), and proximal ileal VH:CD (P = 0.49) were observed between dietary treatments (Table 1). Likewise, there was no evidence of differences in distal ileal VH (P = 0.63), CD (P = 0.53), or VH:CD (P = 0.80) between dietary treatments. In summary, feeding a microencapsulated form of ZnO did not appear to alter small intestinal morphology in weanling pigs compared with conventional, unprotected ZnO.