Replacement of Zinc Oxide with Encapsulated Zinc Oxide on Growth Performance in Early-Weaned Pigs

The objective of the study was to investigate effects of replacing ZnO with coated ZnO on growth performance on early-weaned piglets. Four hundred and twenty-four 18-day-old weaned piglets (initial BW 6.2 ± 0.4 kg) were blocked by body weight and randomly allotted to 1 of 8 treatments, with 7 or 8 pigs (balanced for sex) per pen and 7 pen replicates per treatment in a randomized complete block design. The 8 dietary treatments during phase 1 (d 1 – 14) and phase 2 (d 14 – 28) of the study were: NC (negative control, without antibiotics and ZnO), AB (antibiotics, with 55 ppm carbadox but no ZnO), CTL (control, with 55 ppm carbadox and 3000 ppm ZnO), ZnO (3000 ppm ZnO), and graded levels of coated ZnO providing 563 (cZnO1), 1125 (cZnO2), 1688 (cZnO3), and 2250 (cZnO4) ppm of ZnO. During the third phase of nursery period (d 28 to 42), all pigs were fed a common basal diet without antibiotics and ZnO. All diets were formulated to meet or exceed nutrient specifications of NRC (2012) with corn, soybean meal, dried whey (5-12%), fish meal (2-6%), and spray dried porcine plasma (0-4%) as the main ingredients. Fisher’s least significant difference method was used for multiple comparison. Overall ADG was 353, 357, 370, 392, 346, 343, 376, 396 g/d, overall ADFI was 555, 580, 570, 627, 534, 551, 574, 604 g/d, and overall gain to feed intake was 0.638, 0.610, 0.652, 0.624, 0.651, 0.624, 0.656, 0.658 for NC, AB, CTL, ZnO, cZnO1, cZnO2, cZnO3, cZnO4, respectively. There was a linear increase (p < 0.05) in ADG and ADFI during phases 1 and 2 and the whole experimental period with increasing levels of coated ZnO, whereas feed efficiency was not affected (P > 0.05) by levels of coated ZnO. During phases 1 and 2, piglets fed diets containing 3000 ppm ZnO or 2250 ppm coated ZnO had greater (P < 0.05) ADG compared with the NC, AB, cZnO1, or cZnO2 group. Piglets in the 3000 ppm ZnO or 2250 ppm coated ZnO group had higher (p <0.05) ADFI in phase 2 in comparison with the other 6 groups. Piglets fed diets containing 1688 and 2250 coated ZnO had greater overall feed efficiency than the AB group. In conclusion, 1688 to 2250 ppm coated ZnO may replace 3000 ppm ZnO in the nursery diet under our experimental condition.