interest in the serum color as an indirect criterion of selection of digestive efficiency in chickens improving the digestive efficiency of birds is becoming increasingly important with the diversification of feedstuffs used in poultry diets compared with timeconsuming chemical analyses that were previously used to measure digestive efficiency nearinfrared spectroscopy has been a great advance as it was fast and thus allowed measurements to be taken from a large number of animals as required for genetic studies however it still implies to rear the birds in cages to collect feces which is questionable in terms of welfare the purpose of this study was thus to establish whether the serum color could be used as a biomarker of digestive efficiency that would be easy and fast to measure on floorreared animals we first compared the serum color of 2 lines of chickens divergently selected for high or low digestive efficiency when fed with a wheatbased diet digestive efficiency was assessed by nitrogencorrected apparent metabolizable energy color was assessed by the absorbance of the serum between 300 and 572 nm color differed between the 2 lines between 430 and 572 nm which corresponds to the absorption zone of carotenoids such as lutein and zeaxanthin in a second step we estimated the heritability of serum color measurements and their genetic correlations with digestive efficiency taking these parameters into account in our experimental conditions the best trait among those tested that can be used as a biomarker of digestive efficiency is serum absorbance at 492 nm with a heritability estimate of 031 009 and a genetic correlation with digestive efficiency of 084 028