Physiology, Endocrinology, and Reproduction

The deposition of dietary folic acid (FA) into the chicken egg is likely regulated by its conversion to 5-methyltetrahydrofolate (5-MTHF), the predominant form of this vitamin in eggs (>80%). Supplementation of 5-MTHF in the laying hens′ diet may therefore enhance total egg folate concentrations. To this end, a study was conducted using equimolar concentration of either FA or 5-MTHF in diets fed to both Shaver White and Shaver Brown laying hens, to investigate their influence on total egg folate concentrations, and indices of performance and folate status. A total of 24 laying hens (24 weeks) from each strain were randomly assigned to receive 1 of 3 (n=8) dietary treatments: 1) basal diet with no supplemental folate and 2) basal diet + 10 mg/kg FA and 3) basal diet + 11.30 mg/kg 5-MTHF, for 21 days. Production performance, plasma homocysteine, liver, serum and egg folate concentrations were measured. Feed efficiency for birds consuming diet 3 improved (P<0.05) by 11.9 and 10.7% respectively, compared to hens consuming diet 1 and diet 2; while egg weight increased (P<0.05) by 6% compared to diet 1. Plasma homocysteine was lower (P<0.05) by 14.2%, while serum and egg folate were higher (P<0.05) by 78.3 and 61.8% in hens consuming either folate species as compared to control. Liver 5-MTHF was not affected by folate supplementation. Together, these data provide evidence that supplementation of FA and 5-MTHF have equivalent effects in enhancing egg folate concentrations and improving folate status in laying hens. Supplementation of 5-MTHF may improve production performance, but this remains to be determined in larger production studies. The data also support a point of regulation of egg folate deposition that is prior to hepatic folate metabolism, possibly at the level of intestinal folate uptake and metabolism.