Influence of Ration Ingredient on Chromaticity and Stable Carbon Isotope Composition in Eggs

The egg chromaticity could be changed by artificial pigment and natural pigment through determining the yolk RCF values, but the stable carbon isotope (δ¹³C) ratios of eggs were influenced by maize content in ration only and had nothing to do with the carophyll red. So, the origin of pigment in egg could be deduced, which could supervise and manage the laying hens production. 320 hens were selected and assigned to 2 groups, one was called artificial pigment group, the other was called natural pigment group. Each group included 4 treatments with 4 replicates, then fed on basic diets added different quantity of carophyll red and basic diets with different contents of maize respectively for 63 days. The feed samples were collected at first, then the egg samples were collected on the 28th day and the 56th day of trial period. The δ¹³C values of ration, and the RCF values and the δ¹³C values of eggs were determined. The results show that the RCF values of yolks have remarkable changes（P<0.01）with adding or removing carophyll red in artificial pigment group, but the δ¹³C values of yolks have no significant difference (P>0.05). In natural pigment groups, both the RCF values and the δ¹³C values of yolks have remarkable difference (P<0.01) with the increasing or decreasing of maize content in ration. Meanwhile, the δ¹³C values of yolks and the maize content in ation are significantly correlated (P<0.05). It states the δ¹³C values in yolks are mainly influenced by maize content of ration. So, the δ¹³C values of yolks are determined by the main ingridients of ration. The study lays a theoretical foundation for the application of stable isotope analysis technique in egg pigment traceability.