[Effect of vitamin and mineral supplements on the protein utilization of mixtures of corn and beans].

The present study was undertaken to establish the effect of some vitamins and minerals on protein utilization of maize:bean mixtures fed in an 87:13 and 70:30 weight ratio. The experiments were carried out by feeding such diets without thiamine, niacin, pyridoxin, riboflavin and vitamin A and without iron, zinc, iodine and magnesium, alone or in combination. Completely supplemented diets were used as reference. The results indicated better protein utilization from the 70:30 maize:bean mixture than from the 87:13. Even though it was not possible to detect significant differences due to the lack of single nutrients, either vitamins or minerals, probably due to the relatively short experimental period, the results strongly suggest the importance of these nutrients in increasing protein utilization. The same result was true when both mixtures were supplemented with their limiting amino acids lysine, methionine and tryptophan. Furthermore, the addition of these amino acids without vitamins or minerals did not improve protein utilization, suggesting that nutrition is not due to single nutrients but to a nutrient balance. Chemical carcass composition of the rats showed an increased fat accumulation for the animals fed the 70:30 mixture over those fed the 87:13 blend. No explanation was given, and this should be a subject of further research.