Protein and amino acid digestibility, biological value of protein and energy metabolizability of some leaf protein concentrates in chickens.

Abstract

Three leaf protein concentrates (LPCs), A: a mixture of alfalfa and barnyard grass (32.4% CP/DM), B: a mixture of oat and annual meadow grass (38.5% CP/DM) and C: ladino clover (58.4% CP/DM), were investigated for digestibility and biological value of protein. LPCs were used as the sole source of protein to provide about 10% crude protein in the diets given to six 5-month-old colostomized White Leghorn cockerels. The birds fed a protein-free diet voided the metabolic fecal nitrogen of 92mg per 100g of consumed feed and the endogenous urinary nitrogen of 14mg per 100g of body weight. The gross energy, metabolizable energy, true digestibility and biological value of LPCs A, B and C were 18.4, 17.4 and 24.2kJ/g DM; 12.7, 14.1 and 22.3kJ/g DM; 62.0%, 72.4% and 68.9%; and 78.3%, 73.3% and 78.5%, respectively. The ladino clover LPC had a higher metabolizable energy value when compared to the other LPCs, whereas the digestibility and biological value of protein were not so much different between them. According to the amino acid analysis data, the first limiting amino acid was arginine, and the chemical score calculated on the basis of NRC requirements were 75, 91 and 60 in the diets A, B and C, respectively. In LPCs A and B, however, methionine and histidine gave the lowest digestibility instead of arginine. Apparent amino acid digestibilities were about 6% lower than the corresponding true amino acid digestibilities. Total amino acid digestibility was significantly lower in LPC A than in LPCs B and C.