The current work aimed to test the fit hypothesis; does the animal reproductive status have an impact on
the hormonal milieu of the animals and consequently its body metabolic status? In this study, we assessed
the changes in circulating hormones, key metabolites and blood parameters taking place during different
stages of the estrous cycle and pregnancy in Egyptian Barki ewes. An ultrasonographic examination as well
as blood sampling were conducted, before the morning feeding, on clinically healthy cyclic non-pregnant
(n = 7) and pregnant (n = 9) Barki ewes at early- (d 60 ± 5 post breeding [PB]), mid- (d 90 ± 5 PB) and late-(d 135 ± 5 PB) stage of pregnancy. The results showed marked changes in certain biochemical parameters
of sheep blood serum during pregnancy as compared to luteal and/or follicular stages. Pregnancy was
associated with significant higher levels of progesterone, glutathione peroxidase, malondialdehyde, nitric
oxide and HDL. Samples from cyclic animals showed higher levels of insulin, T3, T4, superoxide dismutase
and glucose. Nevertheless, leptin, triglycerides, cholesterol, VLDL, LDL and blood parameters did not vary
between pregnant and non-pregnant animals. From these results we can conclude that the reproductive
state influence on reproductive (progesterone) and metabolic (T3, T4 and insulin) hormonal levels, lipid
peroxidation and body metabolism, which could have long-lasting consequences and therefore should
be taken into consideration during the early prediction and/or diagnosis of metabolic diseases related to
disturbance in energy balance and/or oxidative stress in Barki ewes.