Based on bone manganese (Mn) accumulation during a 14-day feeding period. Mn bioavailability in a Mn-proteinate product was judged to be not significantly different than that provided by MnSO4.H2O. Bone and bile Mn concentrations were reduced markedly when 10% wheat bran was added to a phytate and fiber-free casein-dextrose diet that contained 1,000 mg/kg supplemental Mn from either MnSO4.H2O or the Mn-proteinate.