THE PROFILES OF WEEKLY PROGESTERONE AND STRADIOL CONCENTRATIONS DURING PREGNANCY IN EWES : 2. THEIR CORRELATIONS WITH MAMMARY GROWTH INDICES AT PARTURITION
Fifteen pregnant (9 and 6 carrying a single and multiple fetuses, respectively) and 5 nonpregnant ewes, as a control, were used to study the correlations of weekly maternal serum progesterone and estradiol concentrations during pregnancy with mammary growh indices at parturition. Blood samples were drawn weekly (weeks 0 to 20) during gestation period for determination of progesterone and estradiol concentrations. The experimental ewes were sacrificed at parturition to determine mammary growth indices (mammary dry fat-free tissue [DFFT], DNA, RNA, and collagen). Concentrations of progesterone at week 1 and weeks 3 to 19 of pregnancy positively correlated with mammary DFFT, DNA, and RNA at parturition. Maternal serum progesterone concentration at weeks 1, 3 and weeks 6 to 20 of pregnancy positively correlated with mammary collagen at parturition. Concentration of estradiol at weeks 5, 7, 9, and 11 to 20 positively correlated with the mammary DFFT, DNA, RNA, and collagen at parturition. The higher the maternal serum progesterone and estradiol concentration during pregnancy the greater the mammary growth and development at parturition.