Improvement in the Immunity- and Vitamin D3-Activity-Related Gene Expression of Coccidiosis-Challenged Ross 708 Broilers in Response to the In Ovo Injection of 25-Hydroxyvitamin D3

Effects of the in ovo administration of two vitamin D ₃ sources (vitamin D ₃ (D ₃ ) and 25-hydroxyvitamin D ₃ (25OHD ₃ )) on the expression of D ₃ activity- and immunity-related genes in broilers subjected to a coccidiosis infection were investigated. At 18 d of incubation (doi), five in ovo injection treatments were administrated to live embryonated Ross 708 broiler hatching eggs: non-injected (1) and diluent-injected (2) controls, or diluent injection containing 2.4 μg of D ₃ (3) or 2.4 μg of 25OHD ₃ (4), or their combination (5). Birds in the in ovo-injected treatments were challenged at 14 d of age (doa) with a 20× dosage of a live coccidial vaccine. At 14 and 28 doa, the expression of eight immunity-related genes (IL-2, IL-6, IL-10, TLR-4, TLR-15, MyD88, TGF-β4, and IFN-γ) and four D ₃ activity-related genes (1α-hydroxylase, 25-hydroxylase, 24-hydroxylase, and VDR ) in the jejunum of one bird in each treatment-replicate group were evaluated. No significant treatment effects were observed for any of the genes before challenge. However, at 2 weeks post-challenge, the expression of 1α-hydroxylase, TGF-β4, and IL-10 increased in birds that received 25OHD ₃ alone in comparison to all the other in ovo-injected treatment groups. Additionally, the expression of 24-hydroxylase and IL-6 decreased in birds that received 25OHD ₃ in comparison to those injected with diluent or D ₃ alone. It was concluded that the in ovo injection of 2.4 μg of 25OHD ₃ may improve the intestinal immunity as well as the activity of D ₃ in Ross 708 broilers subjected to a coccidiosis challenge.