Effect of reducing dietary crude protein level on the uptake and metabolic utilization of trace minerals in...

A study was conducted to evaluate the effect of a low-protein diet containing 19.5% crude protein (CP) on the growth performance, trace mineral contents in tissue and extra, and the activities and mRNA expression of enzymes relating to mineral metabolism in the liver of Arbor Acres (AA) broilers. A completely randomized design was adopted in this study. A total of 72 one-day-old AA male broilers were randomly assigned to one of two treatments (six replicate cages with six chicks per cage). The birds were fed the corn-soybean meal diet with 21.5% CP (control) or 19.5% CP for 21 d. Data were analyzed statistically using a T-test in SAS software (version 9.4, SAS Institute Inc., Cary, NC). The results showed that no differences were observed in average daily feed intake, average daily gain, feed conversion ratio, nitrogen retention rate, Cu, Fe, Mn, and Zn contents in the tibia, Fe, Mn, and Zn contents in the liver, and Cu and Zn contents in excreta of broilers between the two treatments (P > 0.05). Nevertheless, compared with broilers fed the control diet, broilers fed a low-protein diet had lower Zn content in serum, and Cu content, total antioxidant capacity, and mRNA expression level of catalase in the liver (P < 0.05), but higher Fe and Mn contents in excreta (P < 0.05). The results indicate that lowering dietary CP concentration from 21.5% to 19.5% had no adverse effect on growth performance, but reduced Zn absorption and hepatic antioxidant ability, as well as the metabolic utilization of Cu, Fe, and Mn in white-feathered starter broilers.