Zinc Source and Copper Level in Low Acid-binding Capacity Diets for Nursery Pigs as Alternatives to Pharmacological Zinc Oxide

This study examined the effects of different zinc (Zn) source and copper (Cu) levels as alternatives to pharmacological levels of ZnO in low acid-binding capacity (ABC)-4 diets on growth performance and fecal dry matter (DM) of nursery pigs. A total of 360 weaned pigs (18 ± 1 d old; initially 5.7 ± 0.2 kg) were randomly assigned to one of six treatments (12 pens/treatment; 5 pigs/pen) with three body weight (BW) blocks. The experiment consisted of phase 1 (d 0 to 10), phase 2 (d 10 to 24), and phase 3 (d 24 to 46) diets. Treatments were arranged in a 2 × 3 factorial consisting of three Zn treatments combined with two Cu levels. Zinc treatments included low (150 mg/kg) and high (800 mg/kg) levels of Zn from potentiated ZnO (pZnO, HiZox®, Animine Precision Minerals, Annecy, France; source with small aggregates and agglomerate particles) for both phase 1 and 2, and pharmacological levels of Zn from standard ZnO (Maximo720; Zinc Nacional, Monterrey, Mexico; source with large and dense particles) at 3,000 and 2,000 mg/kg for phases 1 and 2, respectively. Copper treatments consisted of low (18 mg/kg) and high (150 mg/kg) levels of Cu from monovalent Cu2O (CoRouge; Animine). In phase 3, experimental diets were divided according to Cu inclusion, with either 18 or 150 mg/kg of Cu from Cu2O®, while all diets contained 150 mg/kg of Zn from pZnO. The basal diet ABC-4 levels were 199 and 248 meq/kg for phases 1 and 2, and 437 meq/kg for phase 3. The ABC-4 value of each treatment diet changed depending on the addition of Zn and Cu. There were no significant Cu × Zn interactions, nor main effects of Zn for any performance variables observed throughout the experiment. However, significant Cu main effects were observed. In phase 1 and overall (d 0 to 46), pigs fed high-Cu2O diets tended to have greater G:F compared to those fed low-Cu2O (P < 0.10). On d 10, pigs fed low pZnO had higher fecal dry matter than those fed pharmacological doses of standard ZnO (P < 0.05). For phase 3 and overall (d 0 to 46), pigs fed high Cu2O diets had greater ADG compared to those fed low Cu diets (P < 0.05). In conclusion, under a low ABC-4 diet formulation strategy, reduced levels of pZnO achieved growth performance comparable to pharmacological ZnO, while high-Cu2O supplementation further enhanced growth performance. These results also indicate that pharmacological ZnO provided limited benefit to fecal DM during the early post-weaning period when pigs are fed low ABC-4 diets.