Effects of incubation temperature and sex on local and systemic immune parameters in broiler chickens

1. The current study investigated the effects of different egg incubation temperatures and sex on local and systemic immune parameters <i>post</i>-hatch in Ross 308 broilers. It was hypothesised that increased or decreased incubation temperature could support the developing immune system. 2. In total, 405 eggs from a 49-week-old breeder hens were divided into three groups and incubated between embryonic days (ED) 4–7, at different temperatures: normal/control (37.5°C), lower (36.5°C) or higher (38.5°C). After hatching, the broilers were sexed and reared for 35 d. Blood samples and tissue samples from the spleen and ceacal tonsils were analysed for various immune parameters from a sub-set of the chickens representing all treatments. 3. The results showed that the 38.5°C treatment provided significant immunomodulation by altering the number, percent and expression of surface receptors in various leukocyte subsets. However, interpreting the observed differences in terms of immunocompetence was ambiguous. The 36.5°C treatment showed a potential improvement in immune function by increasing the opsonisation potential of blood serum indicating a potential beneficial effect of the lowered temperature. 4. Regarding immunological differences between sexes, females had a higher percentage of MHC-II positive monocytes/macrophages and a higher cell surface expression of MHC-II in the caecal tonsils than males.