Studies on nutritive value of left protein from lucerne (Medicago sativa). 3. Supplementation of rat diets based on wheat.

Abstract

AbstractGrowth responses of weanling female rats for 4 to 8 weeks, and the Protein Efficiency Ratio (PER) for 4 weeks were measured for diets of wheat flour (W) and three mixtures of wheat and lucerne leaf protein (W:LP). Increasing the proportion of leaf protein in, and the protein content of the mixtures led to progressive improvements up to 4 weeks, but there was no significant difference in weight gain after 8 weeks between the supplemented diets.4‐week growth and PER studies using diets of wheat, lucerne leaf protein and mixtures of these two substances in various proportions, but all containing around 10% protein, showed that the diets containing 40–60% of the mixture‐protein derived from lucerne preparations promoted significant responses the best results being given by the W50:LP50 mixture. The content of some of the essential amino acids in these diets, on calculation, showed that in the W50:LP50 mixture the deficiency (in comparison with the F.A.O. Reference Protein) of threonine, valine, isoleucine and lysine in wheat is eliminated. Both wheat and lucerne leaf protein are deficient in methionine; cystine, of which there is an adequate amount in wheat but not in lucerne leaf protein, becomes marginal at a protein ratio of W80:LP20 and is deficient by only 10% in the W50:LP50 mixture. The optimum response obtained from the latter indicates that it contains the best balance of essential amino acids possible with these two substances. The decrease in the efficiency of mixed diets containing more than 50% of the protein from lucerne preparation is possibly due to the progressively increasing deficiency in total S‐containing amino acid content.