A high manganese content in a casein diet, similar to that in a lupin-containing diet (about 0.3 g/kg), had no adverse effects on the utilization of dietary protein and retention of Mn, Mg, Fe and P in rat body. The addition of 10% lupin hulls caused a significant decrease in the digestibility (89.5 vs. 92.8%) and protein efficiency ratio (2.8 vs. 3.03), and lowered the retention of mineral components in comparison with the control diet. Manganese retention declined from 3.84 to 1.22% of intake, phosphorus from 30.9 to 24.9%, magnesium from 24 to 12.8%, and iron from 26.6 to 22.1% . The addition of sodium phytate to the casein diet containing lupin hulls decreased only the bioavailability of manganese (from 1.22 to 0.64%) and phosphorus (from 24.9 to 23.0%). The utilization of P, Mg and Fe was the lowest in animals fed the diet containing white lupin seeds.