Low dose of coated zinc oxide is as effective as pharmacological zinc oxide in promoting growth performance, reducing fecal scores, and improving nutrient digestibility and intestinal morphology in weaned pigs

This study was conducted to evaluate the effects of coated zinc oxide on growth performance, nutrient digestibility, fecal scores, minerals concentrations in serum, fecal zinc, intestinal morphology, and selected microbial population in weaned pigs. A total of 192 crossbred [(Yorkshire × Landrace) × Duroc] weaned pigs (7.42 ± 0.97 kg) were randomly assigned into one of the following dietary treatments: (1) negative control (NC): basal diet; (2) positive control (PC): NC + 2500 mg/kg conventional zinc oxide; (3) CZO300: NC + 300 mg/kg coated zinc oxide; (4) CZO500: NC + 500 mg/kg coated zinc oxide; (5) CZO1000: NC + 1000 mg/kg coated zinc oxide; (6) CZO2000: NC + 2000 mg/kg coated zinc oxide. Each treatment had 8 replicate pens, with 4 pigs per pen. Pigs fed PC, CZO500, CZO1000, and CZO2000 diets had higher (P < 0.01) average daily gain (ADG) than those fed NC diet during days 0-21. During days 0-42, supplementation of coated zinc oxide at levels of 500, 1000, and 2000 mg/kg increased ADG compared with NC treatment (P < 0.05). Pigs fed PC, CZO300, CZO500, CZO1000, and CZO2000 diets had lower (P < 0.01) fecal scores compared with those fed NC diet during weeks 1, 2, and 3, but no significant difference was observed among coated zinc oxide-supplemented diets. Pigs fed the PC, CZO1000, or CZO2000 diet had greater (P < 0.05) coefficient of total tract apparent digestibility of dry matter than pigs fed NC diet. Compared with pigs fed NC diets, pigs fed the PC diet or coated zinc oxide-supplemented diets had increased (P < 0.01) serum and fecal zinc concentrations. Duodenal villus height and ratio of villus height to crypt depth of pigs fed PC, CZO1000, and CZO2000 diets were higher (P < 0.05) than those of pigs fed NC diet, whereas no significant differences were observed between pigs fed the PC, CZO1000, and CZO2000 diets. In conclusion, supplementing low doses (500-1000 mg/kg) of coated zinc oxide were as effective in stimulating growth, alleviating post-weaning diarrhea, and improving small intestinal morphology and nutrient digestibility as when a pharmacological level of zinc oxide (2500 mg/kg) was included. Additionally, low doses of coated zinc oxide reduced the amount of zinc excreted into the feces compared with 2500 mg/kg conventional zinc oxide.