Effects of Dietary Folic Acid Supplementation on Productive Performance, Egg Quality, Flavor, and Folate Species Deposition in Laying Hens

This study explored the effects of varying levels of dietary folic acid (FA) supplementation on laying performance, egg quality, egg yolk flavor, and the deposition of four folate forms in eggs. A total of 336 Hy-Line Brown layers were randomly divided into seven groups and fed basal diets supplemented with FA at doses of 0, 0.25, 0.5, 1, 5, 10 and 15 mg/kg, respectively. The results suggested that dietary FA supplementation exerted no notable effects on laying performance or egg quality. Electronic nose analysis of egg yolk flavor revealed that high FA supplementation levels (10 and 15 mg/kg) linearly decreased sensor response scores to organic sulfides, aroma constituents, alkanes, and alkane aromatic components compared to the low-dose FA groups (0 to 0.5 mg/kg). Analysis of egg yolk folates identified four folate forms with the following proportions: 5-methyltetrahydrofolate (5-MTHF, 79–84%), 10-formylfolic acid (10-FMF, approximately 10%), folic acid (<5%), and 5-formyltetrahydrofolic acid (5-FMTHF, <3%). Linear and quadratic relationships were observed between dietary FA supplementation levels and the content of three folate forms (5-MTHF, folic acid, and 10-FMF) in egg yolk and whole eggs. Notably, the egg highest total folate content (119.60 μg/100 g) was observed in hens fed diets containing 15 mg/kg FA at week 4, although this was not significantly different from hens fed 5 mg/kg FA at week 6. In summary, 5 mg/kg FA was the optimal dose to achieve saturated total folate content in eggs without altering egg flavor.