(Hassanzadeh et
al., 2004). The difference in partial pressures of 4% in the
study by Hassanzadeh et al. (2004) was the same as in
the present study, where it was concluded that HT was
not affected by O2 at all. In the study by Hassanzadeh et
al. (2004), eggs were incubated at a constant MT of 37.8°C
at both altitudes. Because it was observed that eggs incubated
at high altitude experience more difficulties to exchange
heat (Meijerhof, 2002), these eggs are likely to be
incubated at higher EST, which may have decreased HT
as a result. Next to EST, incubation weight loss was also
not measured in the study by Hassanzadeh et al. (2004),
which could have explained the lower BW of chicks
hatched at high altitude. Increased weight loss may also
have reduced YFB of chicks incubated at high EST in