Effects of dietary supplementation of a zinc oxide product encapsulated with lipid on growth performance, intestinal morphology, and digestive enzyme activities in weanling pigs

• Effects of dietary lipid (10%)-coated (LC) ZnO vs. ZnO were studied in weanling pigs.
• ADG increased due to 139-ppm LC ZnO (LCZ) and 3125-ppm ZnO (HZ, control: 125 ppm).
• Diarrhea score, which decreased in response to HZ, did not change due to LCZ.
• Zn contents in the liver and serum increased in response to HZ, but not due to LCZ.
• Villus morphology and digestive enzyme activities did not change due to LCZ or HZ.

The present experiment was performed to investigate the effects of a lipid-encapsulated ZnO product (Shield Zn) on growth, intestinal morphology, and digestive enzyme activities in (Yorkshire × Landrace) × Duroc piglets. A total of 408 21-day-old weanling pigs were allotted by sex and body weight to 12 pens, with 34 animals per pen, in a randomized complete block design. The animals were fed a ZnO-free basal nursery diet supplemented with 125 mg ZnO (100 mg Zn)/kg (ZnO-100), 3125 mg ZnO/kg (ZnO-2500), or 139 mg of lipid-encapsulated Shield Zn (100 mg Zn)/kg (Shield Zn-100) for 14 days, after which 24 animals were killed for examination of intestinal morphology and digestive enzyme activities. The average daily gain of the Shield Zn-100 group (207 g/d) was greater (P<0.01) than that of the ZnO-100 group (184 g/d), but was less (P<0.01) than that of the ZnO-2500 group (235 g/d). The average daily feed intake was less in the Shield Zn-100 (326 g/d) than in the Zn-2500 group (367 g/d; P<0.01), not being different between the former and the ZnO-100 group (309 g/d; P=0.23). However, the gain:feed ratio was not influenced by the treatment. The fecal consistency (diarrhea) score subjectively measured by a 3-notch integer scale was greater (P<0.01) in the Shield Zn-100 (1.30) and ZnO-100 (1.31) groups vs. ZnO-2500 group (1.06). Hepatic and circulating Zn concentrations were less (P<0.01) in the Shield Zn-100 and ZnO-100 groups vs. ZnO-2500, not being different between the former two groups. The villus height, crypt depth and villus height:crypt depth ratio in the duodenum, jejunum, and ileum as well as specific activities of sucrase, maltase, leucine aminopeptidase in these intestinal regions and amylase and trypsin activities in the pancreas were not influenced by the dietary treatment. In conclusion, the present results indicate that supplementation of Shield Zn at a physiological level is superior to that of native ZnO at the same level in supporting weight gain of weanling pigs, but that the former is inferior to pharmacological ZnO in the growth-enhancing and diarrhea-suppressing effects.