Abstract
This study was aimed to investigate the effects of different dietary zinc sources on the diarrhea rate, intestinal morphology, immune indexes and intestinal microbial composition of weaned piglets. A total of 240 weaned piglets (Duroc × Landrace × Yorkshire), at the age of 21 days, were randomly assigned to five dietary treatments for a four-week feeding trial to determine the effects of different amounts of tetrabasic zinc chloride (TBZC) supplementation on intestinal morphology, intestinal immune indices and intestinal microflora in weaned piglets, compared with the pharmacological dose of ZnO. The dietary treatments included a negative control (CON), (T1) ZnO (ZnO, 1500 mg/kg), (T2) tetrabasic zinc chloride (TBZC, 800 mg/kg), (T3) tetrabasic zinc chloride (TBZC, 1000 mg/kg), and (T4) tetrabasic zinc chloride (TBZC, 1200 mg/kg). Each treatment comprised six replicate pens, with eight pigs (four barrows and four gilts) per pen. Dietary TBZC of 1200 mg/kg improved the duodenum villus height, jejunum villus height and crypt depth of ileum, and increased the ratio of villus height to crypt depth of ileum (p < 0.05). The dietary supplementation of TBZC at a dosage of 1200 mg/kg has the potential to increase the levels of immunoglobulin G (IgG) and immunoglobulin A (IgA) in the duodenal mucosa. Furthermore, it shows a significant increase in the levels of immunoglobulin A (IgA) in the ileum. Compared with CON, TBZC significantly (p < 0.05) decreased pH values of stomach contents. It also increased the number of Firmicutes in intestinal contents. Compared with CON, the abundance of Firmicutes in jejunum contents of other treatments was significantly improved (p < 0.05), while the abundance of Proteobacteria in ileum contents of high-zinc treatments (T2 and T5) was decreased (p < 0.05). In conclusion, dietary TBZC of 1200 mg/kg improved the digestibility of crude protein in weaned piglets, altered the intestinal morphology of piglets, changed the intestinal microflora of piglets, reduced the diarrhea rate, and significantly improved the development of the small intestine of weaned piglets, and its regulation mechanism on intestinal tract needs further study. In summary, TBZC is likely to be an effective substitute source for the pharmacological dose of ZnO to control diarrhea in weaned piglets.