Characterization of Dosage Levels for In Ovo Administration of Innate Immune Stimulants for Prevention of Yolk Sac Infection in Chicks

Innate immune stimulants, especially toll-like receptor (TLR) ligands and agonists, are the main players in the initiation of innate immunity and have been widely studied as alternatives to antibiotics to control infection. In the present study, we characterized the dosage levels of various innate immune stimulants, including unmethylated cytosine-phosphate-guanosine dinucleotide -containing oligodeoxynucleotides (CpG ODN), polyinosinic-polycytidylic acid (poly I:C), cyclic polyphosphazene 75B (CPZ75B), avian beta-defensin 2 (ABD2), and combinations of these reagents given in ovo. Data derived from a series of animal experiments demonstrated that the in ovo administration of 10-50 mu g CpG ODN/embryo (on embryonic day 18) is an effective formulation for control of yolk sac infection (YSI) due to avian pathogenic Escherichia coli (E. coli) in young chicks. Amongst the different combinations of innate immune stimulants, the in ovo administration of CpG ODN 10 mu g in combination with 15 mu g of poly I:C was the most effective combination, offering 100% protection from YSI. It is expected that the introduction of these reagents to management practices at the hatchery level may serve as a potential replacement for antibiotics for the reduction of early chick mortality (ECM) due to YSI/colibacillosis.

Automated summary

In this study, the dosage levels of various innate immune stimulants were characterized, and it was found that the administration of 10-50 μg CpG ODN/embryo is effective in controlling yolk sac infection caused by avian pathogenic E. coli. Additionally, the combination of 10 μg CpG ODN and 15 μg poly I:C was the most effective in preventing yolk sac infection.