Effect of dietary manganese and age on tissue trace mineral composition of broiler-type chicks as a bioassay of manganese sources.

An experiment was conducted with 144 Cobb broiler-type chicks in a 4 X 3 factorial arrangement of treatments to investigate the effects of dietary manganese (Mn) and age on trace mineral composition in tissues. Day-old chicks were fed a basal corn-soybean meal diet (112 ppm Mn) supplemented with 0, 1000, 2000, or 3000 ppm Mn as manganese sulfate monohydrate (MnSO4 X H2O) for 1, 2, or 3 weeks. There were two pen replications per treatment combination and six chicks per pen. Liver, kidney, pancreas, skeletal muscle, and bone were excised from 4 chicks per replication. Plasma was pooled from the remaining 2 chicks, and all samples were frozen for subsequent mineral analysis. There was a reduction in average daily feed intake (P less than .05) at the 3000 ppm dietary level accompanied by a nonsignificant decrease in average daily gain and an increase in feed per unit gain. Tissue Mn increased (P less than .001) for all tissues as dietary Mn increased. Tissue Mn concentration was reduced with age in kidney, pancreas, muscle (P less than .001), and plasma (P less than .05). Manganese in bone was lowest (P less than .01) at 1 week of age. Of those ages tested, the optimum for bioassay based on lambda criterion values appeared to be 3 weeks. The highest lambda criterion values were obtained at 3 weeks of age in kidney followed by bone at 2 weeks. High dietary Mn increased copper (Cu) concentration in liver (P less than .05) and plasma (P less than .05) and reduced iron (Fe) in pancreas (P less than .001). Liver Fe was lower (P less than .001) at 3000 ppm than at 1000 or 2000 ppm dietary Mn. Plasma zinc (Zn) was higher (P less than .05) at all supplemental Mn levels than the unsupplemented control, and kidney Zn increased (P less than .001) at 3000 ppm dietary Mn.