Evaluation of the efficacy and safety of cysteamine-chelated zinc in weaned-to-finished pigs

This study aimed to evaluate the efficacy and safety of dietary cysteamine-chelated zinc (Zn-CS) supplementation in weaned-to-finished pigs. In total, 144 weaned piglets (45 days old, 10.12 ± 0.03 kg) were randomly assigned to four dietary treatments: A basal diet or the basal diet supplemented with 150, 300, or 450 mg/kg Zn-CS. Supplementation with 150 or 300 mg/kg Zn-CS significantly improved the average daily gain and apparent total tract digestibility of several indexes (p < 0.05), and reduced the feed-to-gain ratio (p < 0.05). Although pigs receiving 300 mg/kg showed the highest body weight numerically on Day 14, secondary analysis of overall growth (Days 0–28) indicated an inflection point, with 150 mg/kg producing the optimal improvement. Moreover, histological examination revealed intact intestinal structures across groups; notably, 150 mg/kg Zn-CS significantly increased jejunal villus height, villus height-to-crypt depth ratio, and the expression of tight junction proteins (p < 0.05), reflecting enhanced intestinal barrier integrity. Unlike traditional high-dose ZnO and cysteamine, which may cause epithelial damage or organ toxicity, long-term Zn-CS supplementation showed no pathological effects on the small intestine, liver, or kidney (p > 0.05), confirming its safety. Furthermore, Zn-CS supplementation promoted fast-twitch muscle fiber expression and improved carcass traits, including hot carcass weight and carcass length, along with a higher pH at 24 h postmortem (p < 0.05), suggesting benefits for muscle growth and meat quality. Collectively, these results demonstrate that dietary Zn-CS at 150 mg/kg is a safe and effective strategy to enhance growth performance, nutrient absorption, intestinal health, and meat quality in pigs.