Study of keratin hair of domestic cat under methionine and cystine experimental diet using FT-Raman spectroscopy

Abstract FT-Raman spectroscopy has been extensively used to study human keratotic biopolymers, such as skin, nail and hair, since the disulfide bonds of keratin protein is Raman-active vibrational mode. In this context, animal hair can also be evaluated by Raman spectroscopy, for the main protein is keratin. In this study, domestic cats were submitted to an experimental diet with different levels of methionine and cysteine; then their hair was evaluated by using FT-Raman spectroscopy on the first and on the last day of the diets. The results were compared with tensile rupture measurements. They showed that FT-Raman spectroscopy was able to monitor disulfide bonds (510 cm −1 ) and keratin protein conformation (amide I) in different sulfur amino acids levels, indicating that the levels above the minimum recommended were not efficient to improve the hair quality.