Archiva Zootechnica vol. 9, 2006 Contributions to the study of the leaf protein value in different mulberry varieties Alexandra Matei 1 , Doina Brailoiu Tanase 1 , Cristina Diaconescu 2 , Marilena Constantinescu 1 , M. Dolis 32 1 SERICAROM SA- Research Department Bucharest, Romania 2 University of Agricultural Sciences and Veterinary Medicine Bucharest, Romania 3 University of Agricultural Sciences and Veterinary Medicine Iasi, Romania ABSTRACT Mulberry leaf exclusively assures the growth and development of the silkworm larvae, being considered a complete value nutrient, so that the knowledge of its nutritional status is of great interest. The experiment was made in order to study the mulberry leaf protein value of the mulberry varieties: China 32, Eforie, Ichinose, Ucraina 107 and Kayrio Nezumigaeshi. The commercial silkworm hybrid “Triumf” was also utilized in experiment. The content of the protein substances in mulberry leaves, considered as the first step in the study of nutritive value, varied according to the mulberry variety and age of the leaves, being in average 7.93%. The total dry matter has increased together with the leaf age and was in average 30%, ranging from 28.08% to 31.53%. Concerning the protein content, the mulberry leaf reaffirms as a valuable nutrigenous source. The mulberry variety Ichinose showed the highest protein content (23.99%), followed by variety Kayrio Nezumigaeshi (23.53%). The total amino acids content in mulberry leaves changed in accordance with age of the leaves, providing the nourishing needs of the larvae. So, among of the four main amino acids: glycine, alanine, serine and tyrosine which form 90% of silk proteins, about 32% is glycine, 31% is alanine, 16% is serine and 11% is tyrosine. The most efficient mulberry varieties, estimated on the base of the quantitative and qualitative production, are Ichinose and Kayrio Nezumigaeshi. Key words: mulberry leaf, protein value, dry matter, amino acids INTRODUCTION Thanks to the fact that the mulberry leaf exclusively assures the growth and development of silkworm larvae, being in the group of fodder with complete value (as milk or egg), the knowledge of its nutritive value presents a special interest. The biochemical composition of mulberry leaf was the object of study for many researches which have expressed the nutritive value especially by dry matter and raw protein. Recent researches studied also the digestibility and the