Maternal Serum Concentrations of Several Hormones in Does Bearing Different Fetal Number

Abstract

Twelve Etawah-cross (4 cycling-nonpregnant, 5 single and 3 twin) does, with similar body weight and age, were used to study the effect of fetal number on scrum concentrations of progesterone, cstradiol, triiodothyronine, tetraiodothyronine, and cortisol during the last two months of pregnancy. Blood samples were drawn weekly from jugular vein for honnone analyses using solid-phase technique radioimmtmoassay. The results of the experiment showed that average serum progesterone concentrations in the twin-bearing increased (P<0.01) by 92.0% as compared to those in the single-bearing does while concentrations of
serum estradiol increased (P<0.0l) by 169%. When compared to cycling nonprcgnant docs, serum progesterone concentration in the single- and twin-bearing does increased by 1300 and 2,590%, respectively, while estradiol concentration increased by 684 and 2006%, respectively. Average serum triiodothyronine, tetraiodothyronine and cortisol  concentrations decreased (P<0.0l) by 34.9 and 35.3%, 15.7 and 27.6%, and 44.0 and 43.7% in single- and twin-bearing as compared to those in cycling-nonpregnant docs. There was no difference in serum concentrations of triiodothyroninc, tetraiodothyroninc and cortisol between single and twin-bearing does. It was concluded that the increased fetal number from single to twin increased honnonal stimulation (progesterone and estradiol) for mammary gland growth and development during pregnancy. Pregnancy increased utiliution of metabolic honnones in the cellular level causing the decreased matcmal serum concentrations of triiodothyronine, tetraiodothyronine, and cortisol. However, the increased fetal number in the pregnant does did not seem to affect the utilization of the honnones indicating that honnonal regulations of fetal growth during the second half of pregnancy were independent of matemal endocrine system.