Effect of Dietary Supplementation of Organic Trace Minerals at Reduced Concentrations on Performance, Bone Mineralization, and Antioxidant Variables in Broiler Chicken Reared in Two Different Seasons in a Tropical Region

Two experiments were conducted to study the performance, antioxidant activity, and bone mineral variables in broilers fed organic trace minerals (OTM) at lowered concentrations in the diet. In experiment 1, a total of 1500 day-old broiler male chicks were randomly distributed into six groups with 10 replicates of 25 chicks each and housed in floor pens (1.90 x 1.22 m). One group was fed the maize-soybean meal-based control diet, supplemented with inorganic trace mineral (ITM) premix containing Mn, Zn, Fe, Cu, Se, and Cr at 50, 45, 40, 7.5, 0.30, and 0.25 mg/kg, respectively. The remaining groups of chicks were fed the diets, where the ITM premix was replaced with OTM mix so as to provide the respective minerals at graded levels in the diet (100, 75, 50, 40, and 30% of the control diet). Similarly, in experiment II, a total of 1350 day-old male broiler chicks were divided at random into six groups with 9 replicates of 25 chicks each and fed the maize-soybean meal-based control diet having ITM at levels similar to those of experiment I or the test diets, where the ITM was replaced with OTM so as to provide the minerals at 100, 80, 60, 40, and 20% of the ITM-based control diet. Each diet was fed ad libitum from 0 to 42 days of age. The body weight gain, feed intake, and feed efficiency were not affected by supplementing OTM at 30 and 20% in experiments I and II, respectively. Slaughter variables, activities of glutathione peroxidase and super oxide dismutase, and lipid peroxidation and ferric reducing activity in serum were not affected by supplementing OTM at the lowest level of 20% in the diet. Similarly, bone-breaking strength, ash, and Mn contents were not affected by supplementing OTM at 20% of the mineral concentration in control diet containing ITM. Deposition of Ca, P, Cu, and Fe in tibia ash increased with increased concentration of OTM in the diet. However, Zn content in tibia ash reduced with reduction in OTM level in the diet. Based on the results, it is concluded that trace mineral supplementation in organic form even at 20% of the concentration recommended for ITM may be sufficient in maize-soybean meal-based diet to support the optimum growth, bone ash, bone strength, and serum antioxidant status in commercial broilers.