An enzymatic synthesis and composition of oligomers and co-oligomers comprised of -hydroxy carboxylic acids and -amino acids or peptides is disclosed. In a preferred embodiment, a -hydroxy carboxylic acid with a specific chiral configuration is linked by an amide linkage to a -amino acid specific with a specific chiral configuration or linked by an amide linkage to a peptide made up of -amino acid monomers having identical chiral configurations. Proteolytic enzymes catalyze oligomerization of the -hydroxy carboxylic acid and -amino acid. The degree and distribution of oligomerization varies upon the type and concentrations of different reaction mixtures utilized and upon the length of allowed reaction time. The resultant oligomers may be provided to animals such as ruminants as bioavailable amino acid supplements that are resistant to degradation in the rumen and other animals such as swine, poultry and aquatic animals.