MONITORING THE XANTHOPHYLL PIGMENT CYCLE IN EGG-LAYING HENS

Abstract

Xanthophylls, oxidized carotenes, give some plants and animals their yellow pigmentation. In fowl, xanthophylls accumulate in the skin and egg yolks, with deposition influenced by the hen's egg production cycle and diet. This correlation makes pigmentation patterns a predictive tool for laying activity, allowing poultry producers to non-invasively monitor hen productivity. As hens lay eggs, xanthophylls deplete from pigmentation areas in a defined 30-week sequence. Bleaching occurs as xanthophylls transfer from a hen's skin to egg yolks. Bleaching begins at the vent, followed by the eye ring and earlobes (~15 eggs laid/3 weeks), the beak (15"“35 eggs/8 weeks), the bottom of the paws (65"“70 eggs/12 weeks), the shanks (155"“160 eggs/20 weeks), and concludes at the hocks and top of the toes (180 eggs/30 weeks). At peak egg production, full bleaching is observed, lasting ~52 weeks. Then, a 10-week molting period begins, during which egg production slows and pigmentation returns in the same order it was lost. Xanthophylls appear yellow due to their conjugated systems absorption properties. Visual inspection systems have been used extensively to assess yolk color, and high-performance liquid chromatography (HPLC) has been used to quantify carotenoids in blood and tissue samples. However, visual systems are subjective, and HPLC methods are invasive, requiring blood sampling or bird euthanasia. Raman spectroscopy is proposed as a non-invasive, in situ technique to quantify xanthophylls in hen's skin. Reflectance spectroscopy and corresponding established carotenoid quantification methods are also viable alternatives. Nutritional variability of xanthophyll intake affects deposition and thus potential quantification methods. A proposed two-point flock calibration scale addresses this by using the hens in a flock with the lowest (peak laying) and highest (end molting) pigment levels as endpoints on a scale that other hens would fall within. The proposed method would enable real-time monitoring of xanthophylls in live hens and assignment of hens to a specific stage in their productivity cycle.