Dietary zinc-di-tripeptide enhances zinc relative bioavailability and reduces fecal zinc losses compared to zinc sulfate, without compromising performance of growing pigs.

Zinc (Zn) is an essential trace mineral involved in key physiological processes, and organic Zn sources are proposed to have higher bioavailability than inorganic forms. This study aimed to evaluate the bioavailability of a Zn-di-tripeptide (Zn-di-tripep) chelate compared to Zn sulfate (ZnSO4) on growth performance, apparent total tract digestibility of Zn and Zn concentrations in feces, serum, liver, and bone in growing pigs. Ninety male pigs (Landrace × Large White, 63 day-old, 25.44 ± 0.302 kg body weight [BW]) were used in a randomized complete block design based on BW with 10 pigs per treatment over a 60-day period. Pigs were allocated to a 2 × 4 + 1 factorial design, composed by 2 Zn sources (Zn-di-tripep vs. ZnSO4), 4 levels of dietary Zn (30, 60, 90, and 120 mg/kg diet), and a negative control (no supplemental Zn). Digestibility was assessed using acid-insoluble ash as an internal marker, and relative bioavailability was estimated by linear slope-ratio regression. Data were analyzed using Zn source and level as fixed effects, blocks as random effects, and linear and quadratic polynomial contrasts to assess dose-response. Pigs fed Zn-di-tripep or ZnSO4 showed improved performance (P ≤ 0.05) compared to unsupplemented pigs, particularly for average daily gain (ADG) and average daily feed intake (ADFI). From day 0 to 30, pigs fed Zn-di-tripep exhibited a quadratic response (P ≤ 0.05) for ADG and gain-to-feed ratio (G:F), and a linear increase (P ≤ 0.05) in final BW (FBW) and ADFI. From day 30 to 60, both sources promoted linear and quadratic increases (P ≤ 0.05) in FBW, ADG, and G:F, and 120 mg Zn/kg diets resulted in better performance. Fecal Zn concentrations increased linearly (P ≤ 0.05) with dietary Zn level. Pigs fed Zn-di-tripep showed a slight decrease and increase in fecal Zn (P = 0.105) and liver Zn (P = 0.109), respectively, and higher bone Zn concentrations (P ≤ 0.05) than ZnSO4. Serum Zn increased over time (P ≤ 0.05) in all Zn-supplemented pigs, with a trend (P ≤ 0.10) toward higher concentrations in pigs fed Zn-di-tripep than ZnSO4. Apparent total tract digestibility of Zn showed linear effects (P ≤ 0.05), with positive values only for Zn-di-tripep. In conclusion, dietary Zn-di-tripep supplementation improved Zn digestibility, serum and tissue Zn concentrations, and reduced fecal excretion compared to ZnSO4, suggesting greater bioavailability by allowing a reduction in Zn supplementation (∼34%), without affecting pig performance.