Improvement in the Immunity- and Vitamin D 3 -Activity-Related Gene Expression of Coccidiosis-Challenged Ross 708 Broilers in Response to the In Ovo Injection of 25-Hydroxyvitamin D 3 &nbsp.

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.