Retinyl palmitate does not have an adjuvant effect on the antibody response of chicks to keyhole limpet hemocyanin regardless of vitamin A status.

To determine whether supplementing retinyl palmitate (RP) to vitamin A-deficient or -adequate chicks during vaccination increased the antibody response, an experiment was conducted that used a 2-generational model. White Leghorn chicks were hatched from eggs that contained 1.06 ± 0.13, 1.41 ± 0.14, or 1.90 ± 0.13 μg of retinol/g of egg yolk. Upon hatch, chicks were allotted to a diet that contained 70, 100, or 130% of the vitamin A requirement (1,500 IU/kg). At 14 d of age, chicks were challenged with keyhole limpet hemocyanin (KLH), Freund's incomplete adjuvant (FIA), KLH and FIA, KLH and RP administered in the same injection, or KLH and RP administered at different injection sites. The RP dosage was 7,000 IU/kg of BW, and dosage of the KLH was 1 mg/kg of BW. Chicks were bled and rechallenged at 19 d of age, and a final blood draw was taken at 29 d of age. The IgM and IgG antibody responses to KLH were determined by ELISA, and agglutination was used to determine natural antibody titers. When compared with chicks fed diets that contained 70 and 100% of the vitamin A requirement, the chicks fed 130% of the vitamin A requirement had a lower primary IgM and IgG antibody response (P < 0.02) and the secondary IgG response was significantly lower (P = 0.004). However, administering RP together or separate from KLH did not significantly change the secondary IgM or IgG responses compared with chicks challenged with KLH and FIA (P < 0.01). Moreover, natural antibody titers were not different among dietary treatments (P = 0.91). In conclusion, administration of RP with KLH did not improve antibody response in chicks.