Coated tannin supplementation improves growth performance, nutrients digestibility, and intestinal function in weaned piglets

Coated tannin could improve growth performance, digestibility, and intestinal function of weaned piglets, and it had the potential to replace ZnO applied to farming. To explore the effect of coated tannin (CT) on the growth performance, nutrients digestibility, and intestinal function in weaned piglets, a total of 180 piglets Duroc x Landrace x Yorkshire (28 d old) weighing about 8.6 kg were randomly allotted to three treatments: 1) Con: basal diet (contains ZnSO4); 2) Tan: basal diet + 0.15% CT; and 3) ZnO: basal diet + ZnO (Zn content is 1,600 mg/kg). The results showed that 0.15% CT could highly increase the average daily gain and average daily feed intake of weaned piglets compared with the control group, especially decreasing diarrhea incidence significantly (P < 0.05). Compared with the control group, crude protein apparent digestibility and digestive enzyme activity of the piglets fed with 0.15% CT were enhanced obviously (P < 0.05). Meanwhile, the intestinal villi and microvilli arranged more densely, while the content of serum diamine oxidase was decreased, and the protein expressions of zonula occludens-1 (ZO-1) and claudin-1 were significantly upregulated (P < 0.05). In addition, CT altered the structure of intestinal microbiota and augmented some butyrate-producing bacteria such as Ruminococcaceae and Megasphaera. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) analysis also showed that the abundances of pathways related to butyrate metabolism and tryptophan metabolism were increased; however, the function of lipopolysaccharide biosynthesis proteins was significantly decreased. The results demonstrated that 0.15% CT could improve growth performance, digestibility, and intestinal function of weaned piglets, and it had the potential to replace ZnO applied to farming. Lay Summary Studies in recent years have shown that tannic acid has various biological functions such as astringency, anti-inflammatory effect, and anti-oxidation property, which has good potential to improve diarrhea and intestinal health of animals. However, it can also lead to oxidative moisture absorption, poor palatability, and feed intake reduction when added to feed. Fortunately, coating treatment can effectively solve these problems. Under the above background, we hypothesized that tannic acid can repair the above shortcomings and improve growth and gut health parameters in weaned piglets with the help of coatings. Therefore, this study explored the effects of coated tannin (CT) on the growth performance, nutrients digestibility, and intestinal function in weaned piglets, which aimed to provide a scientific basis for CT replacing ZnO as a green and safe additive in farming and simultaneously also provide a reference for the application of other polyphenols in animals' health.