Replacement of inorganic zinc with lower levels of organic zinc (zinc nicotinate) on performance, hematological and serum biochemical constituents, antioxidants status, and immune responses in rats

AIM: A study was undertaken to investigate the effect of organic zinc (zinc nicotinate, Zn-nic) supplementation (6, 9, and 12 ppm) compared to inorganic zinc (12 ppm) on growth performance, hematology, serum biochemical constituents oxidative stress, and immunity in weaned female Sprague–Dawley rats. MATERIAL AND METHODS: A 48 weaned rats (285.20±1.95 g) were randomly distributed to 4 dietary treatments with 6 replicates in each and reared in polypropylene cages for 10 weeks. Basal diet (BD) was formulated with purified ingredients without zinc (Zn). Four dietary treatments were prepared by adding 12 ppm Zn from ZnCO(3) (control) and 6, 9, and 12 ppm Zn from Zn-nic to the BD. On 42(nd) day, blood was collected by retro-orbital puncture for analyzing hematological constituents, glucose, cholesterol, alkaline phosphatase, total protein, albumin, and globulin and antioxidant enzyme activities. At 43(rd) day, rats were antigenically challenged with sheep red blood cell (RBC) to assess humoral immune response and on 70(th) day cell-mediated immune response. RESULTS: Weekly body weight gains, daily feed intake, blood hematological constituents (white blood cell, RBC, hemoglobin concentration, packed cell volume, mean corpuscular volume, lymphocyte, monocyte, and granulocyte concentration) and serum glucose, total protein levels were comparable among the rats feed Zn from ZnCO(3) and Zn-nic (6, 9, and 12 ppm). Serum cholesterol reduced with organic Zn supplementation at either concentration (6-12 ppm). Serum globulin concentration reduced (p<0.05) with 6 ppm Zn-nic supplementation compared to other dietary treatments. Lipid peroxidation lowered (p<0.05) reduced with 12 ppm organic Zn; thiobarbituric acid reacting substances and protein carbonyls concentrations in liver reduced (p<0.05) with 9 and 12 ppm levels of organic Zn supplementation compared to 12 ppm Zn supplementation from inorganic source. RBC catalase and glutathione peroxidase enzymes activities were highest (p<0.05) in rats supplemented with 12 ppm Zn-nic, followed by 9 ppm. Comparable immune response (humoral and cell-mediated) was observed between 12 ppm inorganic Zn and 9 ppm organic Zn and higher (p<0.05) immune response was noticed at 12 ppm Zn-nic supplementation. CONCLUSION: Based on the results, it is concluded that dietary Zn concentration can be reduced by 50% (6 ppm) as Zn nicotinate without affecting growth performance, hemato-biochemical constituents, antioxidant status, and immunity. In addition, replacement of 12 ppm inorganic Zn with 12 ppm organic Zn significantly improved antioxidant status and immune response.