Effect of supplemental inorganic Zn and Mn and their interactions on the performance of broiler chicken, mineral bioavailability, and immune response.

The purpose of this study was to investigate the interaction and main effects of supplemental Zn and Mn levels on growth, tissue mineral uptake, and immune response in broiler chicken. A basal diet of corn-soybean meal was supplemented with Zn at 40, 80, or 160 ppm and Mn at 60, 120, or 240 ppm in a factorial pattern to constitute nine experimental diets. Each diet was offered to nine replicates of six chicks in stainless steel battery brooders. At 35 days of age, body weight gain, feed conversion efficiency, hock joint scores, tibia weight, tibia strength, and percent ash were not influenced by Zn and Mn levels and their interactions. The concentration of Zn (207-238 ppm) and Mn (11.8-16.3 ppm) in tibia increased linearly with progressive raise of mineral inclusion in diets. Mn at 240 ppm level caused higher retention of Zn in tibia, but not vice versa. Manganese either alone or in combination with Zn (Zn160/Mn120 ppm) significantly reduced Cu retention (10.1-7.2 ppm) in tibia. Even in the hepatic tissue, Zn (93.6-98.4 ppm) and Mn (9.3-10.2 ppm) concentration increased linearly with their levels of inclusion in diets. When Zn and Mn levels were maintained at 4:3 ratio (80:60 or 160:120 ppm), the concentration of Zn (100-106 ppm) in liver was higher, while that of Mn was significantly more with low level of Zn (40 ppm) in diet. However, Mn supplementation at 120 ppm level and above significantly decreased Cu accumulation (19.5-17.1 ppm) in liver, but Mn × Zn interaction had no effect on Cu retention. The immune response measured as antibody titers to sheep RBC increased (5.9-7.9 log(2)) significantly with higher Zn (80 ppm) supplementation and cell-mediated immune response to phytohemagglutinin (0.57-0.78) with Mn level at 120 ppm. In summary, Zn (40 ppm) and Mn (60 ppm) as recommended by NRC was sufficient for broiler performance and bone parameters. Mn complimented Zn retention in tibia and antagonized Cu in tibia and liver tissues. Higher levels of Zn (80 ppm) and Mn (120 ppm) than those recommended by NRC were needed for improved immune response in broilers at 35 days of age.