In this study, biological samples (slaughterhouse material) were collected from 30 sheep and 36 goats and classified according to
gestational stage into either early or late gestation. Samples consisted of allantoic fluid, amniotic fluid, fetal liver, fetal kidney, fetal
thyroid gland, maternal plasma and liver to determine selenium (Se) concentrations throughout gestation. The Se concentrations in
the allantoic fluid, fetal liver and kidney increased significantly (p < 0.01) during late gestation. Concurrently, the Se concentrations
in amniotic fluid, maternal plasma and liver decreased significantly (p < 0.01) over time. Significant (p < 0.01) positive relationships
were recorded between the age of the fetus and Se concentrations in the allantoic fluid (r = 0.57–0.75), fetal liver (r = 0.43–0.59)
and kidney (r = 0.80–0.81) in both sheep and goats. A significant (p < 0.05) positive relationships were also recorded between the Se
concentrations in the allantoic fluid and fetal liver (r = 0.35–0.37), the maternal plasma and liver Se concentrations (r = 0.37–0.57)
between sheep and goats. A significant (p < 0.05) negative correlation was recorded between the Se concentrations in the allantoic
fluid with maternal plasma of sheep (r =−0.41) as well as between the fetal liver and maternal liver Se (r =−0.22 to 0.50) and
a negative correlation (r =−0.42 to 0.43) (p < 0.01) between Se concentrations in the fetal liver and amniotic fluid in both sheep
and goats, respectively. Se concentration in the fetal liver was significantly (p < 0.01) higher than that of the kidney and thyroid. In
the thyroid gland no morphological differences were noted. Strong fetal–maternal relationships in Se concentration were evident
throughout the gestational period and dams seem to sacrifice Se levels in order to maintain that in the fetus. Se concentrations in
the amniotic and allantoic fluids could be used as a possible indicator of the Se status of the fetus throughout gestation.