360. Evaluation of a Magnesium-protected Zinc Source as an Alternative to Conventional Zinc Forms in Weaned Piglets.

Abstract Post-weaning management requires balancing piglet health, growth performance, and responsible mineral use. Pharmacological zinc oxide (ZnO) remains an effective strategy to control post-weaning diarrhea, yet its use is associated with substantial zinc excretion and reduced mineral efficiency. As a potential replacement, the present study evaluated a magnesium-protected zinc source under commercial production conditions. A total of 324 DanBred piglets (Duroc × DB90) weaned at 21 days old were supplemented with zinc from three sources: ZnO (CON), Zn-glycinate + ZnO combination (GLY), or magnesium-protected zinc (MG-ZN), throughout the nursery phases: pre-starter (days 0–14), starter I (days 14–21), and starter II (days 21–46). ZnO levels were reduced as the phases progressed in CON treatment (3000, 2500, and 1500 ppm of Zn), while doses of GLY (Zn-glycinate: 45 ppm of Zn + ZnO: 75 ppm of Zn) and MG-ZN (120 ppm of Zn) remained constant. Each treatment included nine replicates (pens with 12 piglets). Body weight, average daily gain (ADG), daily feed intake (DFI), and feed conversion ratio (FCR) were assessed for each phase and for the overall trial period. Fecal consistency was scored daily from 0 to 3 (0: normal feces, 3: watery feces), and fecal samples were collected on day 14 for microbiota composition and zinc concentration analyses. Data were analyzed using a linear model followed by Tukey test (R software). During the first two phases, no significant performance differences were noticed (P > 0.05). During the starter II phase, CON piglets exhibited higher weight and ADG than GLY (23.75 vs. 21.83 kg; 581 vs. 516 g/d; P < 0.05), with MG-ZN showing intermediate performance (23.22 kg; 550 g/d; P > 0.05). During the total period, ADG followed a similar pattern (CON: 406 vs. GLY: 364 g/d; P < 0.05), with MG-ZN showing an intermediate value and not different from CON (394 g/d; P > 0.05). MG-ZN group tended to lower average fecal score versus GLY (1.24 vs. 1.40; P < 0.10) and displayed a lower prevalence of watery feces in relation to that same group (52 vs. 80%; P < 0.05), performing similarly to CON for both evaluations (1.35; 49%; P > 0.05). For microbiota diversity indices, beneficial genera such as Lactobacillus and Prevotella were numerically higher in CON and MG-ZN (P > 0.05). Zinc excretion was substantially reduced in MG-ZN piglets, with fecal zinc level 84% lower than CON and 24% lower than GLY (1.01 vs. 6.48 vs. 1.33 g/kg, respectively; P < 0.001). Overall, magnesium-protected zinc supported post-weaning growth and gut health comparable to pharmacological ZnO and superior to Zn-glycinate approach, while substantially reducing fecal zinc excretion, indicating that this form of Zn could offer a more effective and sustainable alternative to high-dose ZnO in piglet diets.