A novel formulation method was suggested to prepare rumen-protected amino acid by coating chitosan on the particles of hydrogenated fat entrapping amino acid. Chitosan coating that was formed due to the coacervation either by the addition of ethanol or sodium hydroxide to the acetic acid solution of chitosan could increase the retention of amino acid in the fat prills. Both protected methionine and arginine particles showed a sustained release behavior in simulated rumen conditions. In the pH 5.5 buffer, the protected arginine particles coated with chitosan by the coacervation using NaOH could retain about 80% of arginine. When the coacervation with the addition of ethanol was employed, the chitosan-coated particles could retain even 97% of arginine. The chitosan-coated methionine particles prepared by addition of ethanol led to almost the same level (85%) of retention as the commercial product Mepron M85. Both the Higuchi kinetics and the model for the release of agent dissolved in polymer matrix could well describe the control release of protected amino acid.
