Effect of Hormonal Treatments Prior to Lactation on Hormones in Blood Plasma, Milk, and Urine during Early Lactation
Open Access
- 1 April 1977
- journal article
- research article
- Published by American Dairy Science Association in Journal of Dairy Science
- Vol. 60 (4), 557-565
- https://doi.org/10.3168/jds.s0022-0302(77)83902-7
Abstract
Hormonal changes in blood plasma, colostrum, milk and urine were studied through day 25 of lactation in 6, 6 and 2 Holsteins, respectively, to compare normal calving, induced with 25 mg of dexamethasone and estradiol-17.beta., and lactation induced with exogenous estradiol-17.beta. and progesterone. Treatments had no effect on concentrations of prolactin in plasma, but concentrations and daily excretion (.mu.g/day) of prolactin were higher in milk after induced calving. Concentrations of prolactin in colostrum were up to 8 times higher than in blood plasma and decreased subsequently to near ratio of 1:1 in milk. Hormonal treatments had no effect on progesterone in plasma, colostrum or milk. Major differences in the estrogens (estrone, estradiol-17.beta., estradiol-17.alpha., and their total) were observed after day 2 of lactation. Concentrations of the estrogens in plasma and milk, and rates of excretion in urine and milk were lower 3 days after normal calving than after induced calving. Postpartum, estrone decreased proportionately more in milk than estradiol-17.alpha.. Proportions of each estrogen in mammary secretions resembled those in blood plasma prior to day 3 lactation (estrone major) and those in urine thereafter (estradiol-17.alpha. major). Concentrations of estradiol-17.alpha. in milk were 3-10 times higher, but total estrogen was only about twice higher than in blood plasma.Keywords
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