Evaluation of zinc methionine for use in weanling pappy diets

Weanling puppies are in a physiologically stressful state, and zinc is important in maintaining a healthy immune system and adequate growth. Differences in bioavailability exist among dietary zinc sources that could impact their physiologic effects. The objective of this research was to determine if an organic zinc source (Zinpro zinc methionine [ZnMET]; Zinpro Corp, Eden Prairie, MN) was more bioavailable to weanling puppies than an inorganic zinc source (zinc oxide [ZnO]). Two 28-day blocks of 15 (n = 30) hound-cross puppies (8 weeks old) were used in a randomized, complete-block design. Treatments included (1) control diet (50 mg/kg Zn from dietary ingredients and ZnO); (2) control + 50 mg/kg ZnO; (3) control + 100 mg/kg ZnO; (4) control + 50 mg/kg Zinpro ZnMET; and (5) control + 100 mg/kg Zinpro ZnMET. After receiving the control diet from days 1 to 7, dogs were allocated to one of the five treatments from days 8 to 28. Blood was collected on days 7, 14, 21, and 28. Plasma zinc, alkaline phosphatase (AP) isoenzyme profile, IgG, and IgM levels as well as a complete blood count were determined. Changes from baseline data were analyzed as a repeated measures analysis using the mixed-models procedure of SAS (SAS Institute, Cary, NC). The change in plasma zinc was greater (P <.05) in dogs fed 50 mg/kg Zinpro ZnMET, 100 mg/kg ZnO, and 100 mg/kg Zinpro ZnMET than in control dogs. Weight gain was greater (P <.01 ) for dogs fed Zn-supplemented diets compared with control dogs. Serum concentrations of the bone isoform of AP decreased over time for all dogs. However, there was less of a decrease (P <.05) in dogs consuming 50 or 100 mg/kg Zinpro ZnMET diets. White and red blood cells and IgG and IgM levels were not changed. ZinPro ZnMET may be a more bioavailable zinc source than ZnO.