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Hormone Induced Lactation in the Bovine. II. Dynamics of Injected and Endogenous Hormones¹

Department of Dairy Science, Ohio Agricultural Research and Development Center, Wooster 44691

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-17ß and .125 mg/kg body weight of progesterone. Included with the hormones in trial 1 was a combination of 233 µCi of [6,7-hydro-gen-3] estradiol-17ß and 12 µCi of [4-car-bon-14] progesterone. During trial 2, 2050 µCi of [2,4,6,7 hydrogen-3] estradiol- 17)3 were incorporated with the hormones for one cow and 2344 µCi 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-17ß 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-17ß and 6.0, 87.7, and .25% from [hydrogen-3] progesterone. Estrogen and progesterone in plasma averaged 1.83 and 2.61 ng/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-ß and progesterone absorption, whether in plasma or excreta, were correlated.

¹ Journal Articles: 53–75, Ohio Agricultural Research and Development Center, Wooster 44691; and 6031, Purdue Agricultural Experiment Station, Lafayette, IN 47907.