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) †

SIMPLE SUMMARY: Coccidiosis is still considered one of the main diseases affecting the performance and health of poultry reared under intensive production systems. Vitamin D(3) sources have been shown to reduce the negative effects of a coccidiosis infection with a subsequent improvement in live performance and intestinal immunity. Therefore, the aim of the current research was to explore molecular mechanisms that may play role in an improvement in immunity and vitamin D activity in response to the in ovo injection of vitamin D(3) (D(3)) and 25-hydroxyvitamin D(3) (25OHD(3)) alone or in combination in broilers subjected to a coccidiosis infection. In this study, it was shown that the expression of genes linked to an anti-inflammatory response increased and a pro-inflammatory response decreased in the jejunum of 28-day-old broilers (2 weeks after coccidiosis infection) after an in ovo injection of 2.4 μg of 25OHD(3). Additionally, the in ovo administration of 2.4 μg of 25OHD(3) increased the expression of genes linked to D(3) function. In conclusion, the in ovo administration of 2.4 μg of 25OHD(3) at 18 days of incubation can improve the immunity as well as the D(3) activity of broilers challenged with coccidiosis. ABSTRACT: 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.