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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 uti l ization o f dietary protein and retention o f M n , M g , Fe and P in rat body. The addition o f 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 o f mineral components in comparison wi th the control diet. Manganese retention declined from 3.84 to 1.22% o f intake, phosphorus from 30.9 to 24.9%, magnesium from 24 to 12.8%, and i ron f rom 26.6 to 2 2 . 1 % . The addit ion o f sodium phytate to the casein diet containing lupin hulls decreased only the bioavailability o f manganese (from 1.22 to 0.64%) and phosphorus (from 24.9 to 23.0%). The uti l ization o f P, M g and Fe was the lowest in animals fed the diet containing white lupin seeds. K E Y W O R D S : lupin, manganese, fibre , sodium phytate, protein digestibility, PER, minerals, rats I N T R O D U C T I O N Other wise as other legumes, white lupin is capable of storing manganese in seeds. Hung et al. (1987) found that the concentration of manganese in seeds of white lupin was twenty times higher than in a narrow-leafed variety cultivated in * The research was financed by grant N o 5 S305 035 07 from the Committee for Scientific Research 414 JUSKIEWICZ J., ZDUNCZYK Z. the same soil conditions. The high manganese content together with the seeds phytate and fibre, may decrease the feed value of white lupin (Cheeke and Kelly, 1989; Lantzsch,1990). The excess of manganese in the diet decreases the absorption of iron from the digestive tract and the blood haemoglobin level (Hurley and Keen, 1987). Manganese may compete with iron and magnesium, reducing the activity of many enzymes in metabolic pathways (Miller, 1991). Such disorders were found at high manganese concentrations, exceeding 1 g/kg of pig diets (Batterham, 1979), but information on the metabolic consequences of lower levels of this element (4-6 times in excess of the nutritional requirements of animals), and on the concomitant presence of other factors reducing utilization of dietary minerals, e.g. fibre and phytates, is scarce. The purpose of this study was to investigate the effect of high dietary levels of manganese, fibre and phytates, characteristic of white lupin seeds, on the consumption and utilization of diets and on retention of Mn, Mg, Fe and P by rats. M A T E R I A L A N D M E T H O D S The experiments were carried out on 40 Wistar rats with initial body weight 55.2 + 3.8 g. The experimental groups comprised 8 males housed individually in cages of synthetic glass, at 21-22°C, relative humidity of 50-70% and equal periods of dark and light. The composition of diet is given in Table 1. The control diet did not contain fibre, and the Mn content was in agreement with the nutritional requirements of rats. The source of Mn was manganous carbonate that is one of the components of a standard feed mixture (NRC, 1976). The experimental groups were fed diets containing one, two or three of the additional components, i.e. manganese raised to about 0.3 g/kg (CMn diet), manganese and 10% lupin hulls (CMnF diet), or additional manganese, seed hulls and sodium phytate (CMnFPh diet). The amount of manganese, fibre and phytate was increased to the levels corresponding to their content in a diet containing about 30% white lupin seeds. In diet L, the only source of protein were the seeds of the low-alkaloid variety of white lupin, Bardo. The Mn content in this diet (0.38 g/kg) was slightly higher than in CMn diet (0.3 g/kg). Due to the high Mg content in the lupin seeds, the magnesium content in L diet was twice the nutritional requirement of rats. Protein efficiency ratio (PER) was determined during the 4 weeks of the experiment. True digestibility of protein (TD) was determined during a 5-day faeces collection in the last week of the experiment, the metabolic nitrogen was taken according to Rakowska et al. (1978), i.e. 46.54 mg/rat/5 days. After the growth experiment, the Mn, Mg, Fe and P contents were determined in homogenates of rat carcasses. The retention of elements was determined PROTEIN UTILIZATION FROM DIETS WITH ADDITIVES 415 T A B L E 1 Composit ion o f diets containing casein or lupin seeds, g/kg

journal of animal and feed sciences

The utilization of protein and mineral components of diets containing white lupin or casein supplemented with lupin hulls, manganese and sodium phytate