ABSTRACT Prebiotics and probiotics, either alone or
together (synbiotics), can influence the intestinal microbiota
and modulate the immune response. We aimed
to investigate the effects of prebiotic and synbiotic administration
during the early stage of development on
the histological structures of central (bursa of Fabricius
and thymus) and peripheral (spleen) lymphatic organs
in broilers. We used 800 hatching eggs from meat-type
hens (Ross 308). Prebiotics and synbiotics were administered
in ovo into the air chamber of chicken eggs at d
12 incubation, as follows: 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), or physiological saline (control group, C). In
ovo delivery of prebiotics and synbiotics had no adverse
effect on the development of the immune system in exposed
chickens. Administration of Bi2tos with L. lactis
subsp. cremoris (Syn2) decreased the cortex/medulla
ratio in the thymus and slowed the development of the
cortex in bursal follicles on d 21 posthatching, with consequent
impacts on the primary lymphatic organs. The
above treatment also stimulated germinal centers’ formation
in the spleens of 21- and 35-day-old chickens,
indicating enhanced B-cell proliferation in secondary
lymphatic organs. Syn2 also caused an age-dependent
increase in the spleen/bursa of Fabricius ratio. In conclusion,
the in ovo administration of pre- and synbiotics
at d 12 incubation can modulate the central and peripheral
lymphatic organ development in broilers. This effect
is more pronounced after synbiotic treatment than
in prebiotic-treated groups.