Effect of Chromium Supplementation on Performance, Carcass Characteristics, Blood Biochemistry, and Immune Response of Unstressed Broiler Chickens: a Dose-Response Meta-Analysis

Studies investigating the effects of Chromium (Cr) supplementation on unstressed broiler chickens have reported an inconsistent association between Cr supplementation and broiler chickens' responses. We conducted a dose-response meta-analysis of previous studies to assess the dose-response associations between Cr supplementation and performance parameters, carcass traits, blood metabolites, and immune indices of non-stressed broiler chickens. The results showed that Cr supplementation was not associated with feed intake, body mass gain, and feed conversion ratio. There was a J-shaped relationship between Cr supplementation and carcass relative weight, and Cr supplementation at about 1145 mu g/kg diet produced the highest response. However, supplemental Cr had no effects on the other carcass traits, including breast, leg, abdominal fat, and liver relative weights. There was a strong evidence of nonlinear associations between Cr supplementation and the blood concentration of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol (P < 0.05). The maximum reduction in blood LDL concentration was observed when Cr was supplemented at about 540 mu g/kg diet, and Cr at the dose of 588 mu g/kg of diet caused the greatest enhancement in the blood HDL concentration. However, supplementation with Cr did not change the blood total cholesterol and triglycerides concentrations. Additionally, a strong inverse association was found between Cr supplementation and blood glucose concentration. Furthermore, positive linear associations between Cr supplementation and the relative weight of bursa and thymus and the antibody titer to Newcastle disease vaccine were detected. However, supplemental Cr had no effect on the spleen relative weight and titer against avian influenza vaccine. Findings from this meta-analysis demonstrate that Cr supplementation is positively associated with carcass relative weight, blood HDL concentration, and immune response and inversely associated with blood glucose and LDL concentrations in non-stressed broiler chickens.