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Estradiol concentrations increase in bovine milk in late pregnancy and are correlated with milk fat and protein
Author(s) -
PapeZambito Dana Alyce,
Magliaro Ann L.,
Kensinger Ronald S.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1423-d
Subject(s) - radioimmunoassay , pregnancy , chemistry , milk fat , bovine milk , zoology , endocrinology , blood plasma , medicine , food science , biology , genetics , linseed oil
Estradiol (E 2 ) is present in milk, but the mechanism(s) regulating the appearance of E 2 in milk are not known. The objectives of this study were to quantify E 2 concentrations in plasma and milk samples throughout pregnancy in cows and to determine if the plasma to milk ratio changes during pregnancy. Blood and milk samples were collected from 13 cows every 28 days throughout pregnancy. E 2 was quantified in blood and milk using radioimmunoassay after organic solvent extractions and Sephadex LH‐20 column chromatography. Cows were categorized in the 1 st , 2 nd , and 3 rd trimesters of pregnancy. Proc Mixed and Corr procedures of the Statistical Analysis Software were utilized for statistical analyses. Plasma E 2 averaged 0.55 ± 0.22, 0.86 ± 0.17, and 2.01 ± 0.20 pg/mL and milk E 2 averaged 0.25 ± 0.90, 0.87 ± 0.67, and 5.09 ± 0.61 pg/mL for trimesters 1, 2, and 3, respectively. Plasma and milk E 2 concentrations were significantly higher in trimester 3 compared to 1 and 2 (P < 0.001). Milk E 2 concentrations were positively correlated with milk fat (R = 0.22, P < 0.05), milk protein (R = 0.62, P < 0.001) and plasma E 2 concentrations (R = 0.86, P < 0.001). The plasma to milk ratio of E 2 significantly decreased with ratios of 3.0, 1.7, and 0.6 in trimesters 1, 2, and 3, respectively, suggesting that the mechanism(s) regulating the appearance of E 2 in milk may change during late pregnancy. (USDA Special Research Grant 2003‐34163‐13404).