Ontogeny of allotype synthesis and decay of maternal allotype in young chickens

Impact of Prebiotics and Synbiotics Administered in ovo on the Immune Response against Experimental Antigens in Chicken Broilers

Simple Summary

The immune system of chickens matures in the course of embryonic development. Early in ovo supplementation with bioactive substances leads to the long-term maintenance of a high level of intestine bifidobacteria, reduces the number of detrimental microorganisms in the gut, modulates the central and peripheral lymphatic organ development in broilers, and stimulates gut-associated lymphoid tissues (GALT) development after hatching. In this investigation, we studied whether the early in ovo application (at the 12th day of embryo incubation) of selected bioactives (prebiotics and synbiotics) influences the humoral immune response against experimental antigens, and the delayed-type hypersensitivity (DTH) skin reaction to experimental mitogen. This study demonstrated that the in ovo application of bioactives did not significantly influence the humoral immune response against T-dependent and T-independent model antigens. Prebiotics in chickens immunized with T-dependent antigen (SRBC) protected them from a retarded rise of the IgG concentration. Bioactives reduced the mortality of birds, markedly with inulin (−6.4%), and the DTH reaction to phytohemagglutinin on the 7^th and 21^st day after hatching.

Abstract

The effect of the in ovo application of selected prebiotics and synbiotics on the humoral immune response against T-dependent (SRBC) and T-independent (dextran) antigens and delayed-type hypersensitivity (DTH) to phytohemagglutinin was studied. On the 12th day of incubation, 800 eggs (Ross 308) were divided into five groups and injected into the egg air chamber with prebiotic inulin (Pre1), Bi²tos (Pre2), a synbiotic composed of inulin and Lactococcus lactis subsp. lactis IBB SL1 (Syn1), a synbiotic composed of Bi²tos and L. lactis subsp. cremoris IBB SC1 (Syn2), and physiological saline (control group; C). The chickens were immunized twice at the 7th and 21st day of life with SRBC and dextran. A DTH test was performed on the 7th, 21st, and 35th day. The application of prebiotics and synbiotics had no significant effect on the humoral immune response. SRBC-immunized in ovo Pre1- and Pre2-treated chickens showed significantly higher serum IgG levels than the control. A significant effect on the DTH reaction was detected on the 7th (Pre1 < C) and 21st (Pre2 > Syn2) day. However; Bi²tos may transiently stimulate the cellular immune response on the 21st day. It may be concluded that the application of inulin in an egg air chamber on the 12th day of incubation may stimulate the secondary immune response. The inulin-treated group exhibited a lower mortality rate than the control group.

Distribution of immunoglobulins during embryogenesis in the chicken

Whereas the yolk of freshly-laid eggs contains only IgG, apart from traces of IgA, we were able to measure, on average, 0.145 mg/ml IgM and 0.207 mg/ml IgA in the yolk sac contents of 21-day-old chicken embryos. Up to the 14th embryonic day, IgG is exclusively contained in the yolk sac contents. It was not possible to demonstrate an increase in the amount of immunoglobulins present by comparing the amounts of IgM and IgA in freshly-laid eggs and in the yolk sac contents of 21-day-old embryos. The offspring of hens with experimentally-induced agammaglobulinemia did not begin with the production of the immunoglobulin isotypes IgG, IgM and IgA until after hatching. From these results the conclusion can be drawn that the immunoglobulins IgM and IgA are transferred from the egg white to the yolk sac contents during the last third of embryonic development. Embryonic synthesis of these immunoglobulins can be discounted as a result of this study. Synthesis was found to be initiated between the 2nd and 7th day of life for IgG, between the 2nd and 4th day of life for IgM and between the 6th and 13th day of life for IgA.