Hormone Induced Lactation in the Bovine. II. Dynamics of Injected and Endogenous Hormones

Abstract

Three lactations were induced in two cows in two trials by twice daily subcutaneous injections for seven days. Each injection contained .05 mg/kg body weight of estradiol-17β and .125 mg/kg body weight of progesterone. Included with the hormones in trial 1 was a combination of 233μCi of [6,7-hydrogen-3] estradiol-17β and 12μCi of [4-carbon-14] progesterone. During trial 2, 2050μCi of [2,4,6,7 hydrogen-3] estradiol- 17)β were incorporated with the hormones for one cow and 2344μCi of [1,2,6,7 hydrogen-3] progesterone for the other. Radioactivity from hydrogen-3 and carbon-14 was detected in urine and feces but not in mammary secretion during trial 1. Isotope recovery from [hydrogen-3] estradiol-17β was too low to quantify. By day 17, 90% of the carbon-14 from progesterone was accumulated in feces and 8.0% in urine. For trial 2, recoveries of radioactivity by day 28 from urine, feces, and mammary secretions were, respectively, 32.4, 56.2, and <.002% from [hydrogen-3] estradiol-17β and 6.0, 87.7, and .25% from [hydrogen-3] progesterone. Estrogen and progesterone in plasma averaged 1.83 and 2.61ng/ml during days 2 to 7. Estrogen decreased more rapidly than progesterone post-treatment, but both had decreased by days 16 to 19 when average prolactin of plasma increased. Quantitative measures of estradiol 17-β and progesterone absorption, whether in plasma or excreta, were correlated.