Abstract. The effects of hypoxia at
increased altitude levels on the cardio-respiratory development of broiler
embryos are distinct in comparison with those at sea level. The aim of the
study was to investigate the effects of high incubation temperature (H) and
oxygen supplementation (O) during hypoxic high altitude (HA) on developmental
and physiological traits of embryos and hatching performance of embryonated
hatching eggs in broilers at different embryonic stages. A total of 1280 eggs
obtained from broiler breeders laid at sea level were used. Eggshell quality
characteristics were measured for 20 eggs. The rest of the 1260 eggs were
divided into seven incubation condition (IC) groups (180 eggs per group)
including a control group at 37.8 ∘C and 21 % O2; O
groups, with daily 1 h 23.5 % O2 supplementation at
37.8 ∘C as O0−11, O12−21, and O18−21; H groups
at 38.5 ∘C high incubation temperature at 21 % O2 as
H0−11, H12−21, and H18−21 from days 0 to 11, 12 to 21, and 18 to 21 of incubation,
respectively. All groups were incubated in three different incubators at
hypoxic HA. The effect of IC was determined on eggshell temperature, hatching
performance, embryo development, right ventricular (RV) to total ventricular
(TV) ratio, and blood parameters. The highest egg water loss and embryonic
mortality and the lowest hatchability were in the H0−11 group, which
depended on increased eggshell temperature during incubation. On day 18 of
incubation, due to the decreased egg water loss in the O12−21 and
O18−21 groups, there was an increase in hatchability in fertile eggs
similar to the middle and late H groups. Towards the end of incubation,
embryo/chick weights were not different and RV and TV weights increased in
the treated groups, and the RV ∕ TV ratio changed between 15 and
26 %. At hatching, yolk
sac weight increased in H0−11 and H12−21 groups. The O groups
had the lowest serum tri-iodothyronine (T3) concentration as distinct
from H groups. The serum thyroxine (T4) concentration increased in the
treated groups, dependent on sex of the embryo. Blood hemoglobin
concentration of O groups decreased relative to other groups. The hematocrit
value was the lowest in the O12−21 and highest in the H12−21
groups. The H and O treatments during pre-hatch hypoxic HA condition can be
positively evaluated on physiological traits of embryos after half of
incubation depended on the timing of the IC exposure to the hatching eggs
obtained from broiler breeders at sea level.