Splenic Gene Expression Signatures in Slow-Growing Chickens Stimulated in Ovo with Galactooligosaccharides and Challenged with Heat

Abstract

Galactooligosaccharides (GOS) that are delivered in ovo improve intestinal microbiota composition and mitigate the negative effects of heat stress in broiler chickens. Hubbard hybrids are slow-growing chickens with a high resistance to heat. In this paper, we determined the impact of GOS delivered in ovo on slow-growing chickens that are challenged with heat. The experiment was a 2 × 2 × 2 factorial design. On day 12 of incubation, GOS (3.5 mg/egg) was delivered into the egg (n = 300). Controls (C) were mock-injected with physiological saline (n = 300). After hatching, the GOS and C groups were split into thermal groups: thermoneutral (TN) and heat stress (HS). HS (30 °C) lasted for 14 days (days 36-50 post-hatching). The spleen (n = 8) was sampled after acute (8.5 h) and chronic (14 days) HS. The gene expression of immune-related (<i>IL-2, IL-4, IL-6, IL-10, IL-12p40,</i> and <i>IL-17</i>) and stress-related genes (<i>HSP25, HSP90AA1, BAG3, CAT,</i> and <i>SOD</i>) was detected with RT-qPCR. Chronic HS up-regulated the expression of the genes: <i>IL-10</i>, <i>IL-12p40</i>, <i>SOD</i> (<i>p</i> < 0.05), and <i>CAT</i> (<i>p</i> < 0.01). GOS delivered in ovo down-regulated <i>IL-4</i> (acute <i>p</i> < 0.001; chronic <i>p</i> < 0.01), <i>IL-12p40</i>, <i>CAT</i> and <i>SOD</i> (chronic <i>p</i> < 0.05). The obtained results suggest that slow-growing hybrids are resistant to acute heat and tolerant to chronic heat, which can be supported with in ovo GOS administration.