Effects of heat stress on the immune responses of chickens subjected to thermal manipulation in the pre-hatch period

Abstract Heat stress affects the performance of poultry species and also induces immunosuppression. Chickens can be treated by thermal conditioning to have better heat tolerance. Our purpose was determine effect acute on immune response, i.e. antibody production against Newcastle disease virus (NDV) change in proportion leukocyte components, chicks subjected prenatal conditioning. Eighty as-hatched broiler from same parent stock were used: control (40 incubated at 36.7 °C days 18–20 embryonic life) thermally manipulated (TM) 38.4 day life; 4 h/day). The chickens exposed stress: 19 (31 °C/8 h) 35 (32 °C/10 h). first (day 19) decreased lymphocyte counts significantly increased heterophil ( P < 0.05) both treatments (from 34.25 55% controls 37 60.06% TM chicks). second 35) did not alter profiles chickens. Before stress, all (control TM) presented positive titres NDV vaccination. After 50% samples 40% negative. 80%