Effect of supplementing corn diet for laying hens with vitamin A and trace minerals on carotenoid content and deposition efficiency in egg yolk

This study investigated the effects of supplementing laying hen's diet with vitamin A (5,000, 10,000 and 20,000 IU/kg) and trace minerals (Zn, Mn, Cu, Fe and Se) in inorganic and organic form on the carotenoid content and deposition efficiency in egg yolk. Hen's diet consisted of two commercial dent corn hybrids (soft- and hard-type), which differed in their carotenoid profile. The feeding trial was conducted with 252 Lohmann Brown hens allocated in 84 cages that were randomly assigned to 12 dietary treatments (2 hybrids × 3 vitamin A levels × 2 trace mineral forms). After depletion, hens were fed diets without added pigment for 7 wk. Deposition efficiency was calculated based on the carotenoid content in yolk and diets, yolk weight, egg production and diet intake. Tested hybrids significantly differed in the content of total and individual carotenoids in egg yolk, with the exception of except β-cryptoxanthin. Lutein was the main carotenoid in the soft-type hybrid and zeaxanthin in the hard-type one. Lower vitamin A levels tended to increase the yolk content of provitamin A carotenoids and the deposition efficiency of all carotenoids for both hybrid types. In addition, the highest content of lutein in egg yolk was found when the soft-type hybrid was supplemented with the lowest vitamin A level. In contrast, trace minerals showed a relatively small effect on carotenoid content and deposition efficiency. However, a significant hybrid × vitamin A × trace mineral interaction existed mainly because the hard-type hybrid had the highest deposition efficiency of all carotenoids except α-cryptoxanthin when diet was supplemented with organic trace minerals and the lowest vitamin A level. In conclusion, supplementing hen's diet with the lowest vitamin A level improved the content of provitamin A carotenoids in egg yolk for both hybrids as well as lutein content for the soft-type hybrid, whereas organic trace minerals improved the deposition efficiency of most carotenoids only for the hard-type hybrid.