Enhancements in the expressions of genes associated with the immunity, muscle growth, and antioxidant activity of 14 d broilers in response to the in ovo injection of the Marek's disease vaccine alone or in conjunction with the in ovo and dietary supplemental administration of 25-hydroxycholecalciferol.

Influences the Marek's disease vaccine (MDV) alone or combined with the in ovo and dietary administration of 25-hydroxycholecalciferol (25OHD ₃ ) on the expression of genes associated with the breast muscle deposition, adaptive and innate immunity, and antioxidant and vitamin D activities of 14 d-old broilers were investigated. Four in ovo treatments were: noninjected; commercial MDV-alone-injected (50 μl); or 50 μl of MDV containing 1.2 (MDV+25OHD ₃ -1.2) or 2.4 (MDV+25OHD ₃ -2.4) μg of 25OHD ₃ . Two dietary treatments were a commercial diet containing 25OHD ₃ (250 IU)/kg of feed (control) or the same diet supplemented with additional 25OHD _{3 (} 2,760 IU)/kg of feed (Hy-D diet). One bird per pen (48 total) was sampled at 14 d for determination of the expression of genes involved with the muscle deposition (MyoD1, MyoG, Pax3, and Mrf4), immunity (INF-γ, IL-10, IL-8, IL-1β, and TGF-β4), antioxidant capacity (SOD1, SOD2, GSH-P1, GSH-P7, and CAT), and vitamin D activity (VDR, 1α-hydroxylase, and 24-hydroxylase) in the spleen and pectoralis major (P.major) muscle. The treatment differences were considered significant at P ≤ 0.05. In the P. major, Mrf4 and MyoG were up-regulated in Hy-D-fed birds. Also, the in ovo and dietary 25OHD ₃ sources individually increased SOD2 gene expression in the P. major. In the spleen, the expressions of IL-1β and IL-8 were down-regulated and IL-10 and TGF-β4 gene expressions were up-regulated in Hy-D-fed birds than those commercial-fed broiler. In ovo and dietary 25OHD ₃ sources enhanced vitamin D gene (1α-hydroxylase and 24-hydroxylase) activities in the breast and spleen. In ovo x dietary treatment interactions were significant for the MyoD1, IL-8, Pax3, TGF-β4 genes of the P. major, in which the combined MDV with 1.2 μg of 25OHD ₃ enhanced their expressions in birds fed the Hy-D diet. In conclusion, both 25OHD ₃ sources promoted the expression of genes associated with immunity and P. major growth. It is recommended that both 25OHD ₃ sources can be used to promote the gene expression of 14-day-old broilers in the spleen and breast muscle when MDV administered in ovo.
Competing Interests: DISCLOSURES There is no conflict of interest.
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