Effects of Tetrabasic Zinc Chloride as Alternative to High Doses of Zinc Oxide on Growth Performance, Nutrient Digestibility, Intestinal Morphology, Immune Function, and Gut Microbiota in Weaned Piglets

This study aimed to investigate the effects of dietary supplementation with TBZC on the growth performance, diarrhea incidence, antioxidant ability, immune function, and intestinal health of weaned piglets. A total of 120 weaned piglets were randomly allocated to one of three dietary treatments with six replicate pens and eight piglets per pen: CON-a basal diet; ZnO-a basal diet with 1500 mg Zn/kg from ZnO; and TBZC-a basal diet with 680 mg Zn/kg from TBZC. Following a 42-day period of consuming the zinc-enriched diet, the piglets were switched to a basal diet for the remaining 28 days of the trial. The dietary TBZC increased the average daily feed intake of weaned piglets (ADFI) from days 1 to 14 and the average daily growth (ADG) from days 43 to 70 compared with the ZnO group (<i>p</i> < 0.05). The supplementation with TBZC decreased the acid-binding capacity compared with the ZnO group (<i>p</i> < 0.05). Moreover, dietary TBZC decreased the MDA concentration and increased the GSH-Px concentration on day 14 and increased the SOD activity on day 28 and the GSH-Px concentration on day 70 compared with the ZnO group (<i>p</i> < 0.05). Compared with the ZnO group, the dietary TBAC supplementation increased (<i>p</i> < 0.05) the relative abundance of cecal <i>Lactobacillus</i> spp. and <i>Blautia</i> spp., while decreasing <i>Blautia</i> spp. in the colonic contents; increased (<i>p</i> < 0.05) the relative abundance of <i>Prevotella</i> spp. and <i>Clostridium_sensu_stricto_1</i>; and reduced (<i>p</i> < 0.05) <i>Streptococcus</i> spp. Therefore, replacing 1500 mg/kg of ZnO with 680 mg/kg of TBZC improves growth performance and antioxidant capacity and regulates gut microbes in weaned piglets.