Abstract
Raman spectroscopy has been widely applied in the analysis of biological tissues. In this study, beak cuticle was studied to investigate its compositional and secondary structural changes during the laying period and aging of laying hens. The analysis revealed markedly increased contents of amide I and amino acids (phenylalanine and tyrosine) within the beak during the intense laying period from 17 to 20 weeks. In addition, α-helical protein was also gradually synthesized in this period. The relative area ratio of 1003/1448 cm(-1) (assigned to the vibrations of phenylalanine and organic C-H respectively) was confirmed as an excellent indicator for estimating the start of the laying period. This ratio increased from 0.36 to 0.42 from 17 to 20 weeks. The Raman peak at 1156 cm(-1) was assigned to carotenoids in the beak. The intensities of the 1156 cm(-1) peak significantly decreased during aging. The area ratio of 1156/1448 cm(-1) was successfully applied to estimate ages (still within the laying period) of laying hens. This study shows the potential of using Raman spectroscopy to quantify ages and laying period of birds.