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Concentrations of Progesterone in Milk of Cows Administered an Intravaginal Progesterone Insert

J. R. Chenault^*, R. E. Hornish, Y. C. Anderson, L. F. Krabill, J. F. Boucher^* and M. J. Prough

^* Product Development—Food Animal and
Pre-clinical Development, Pharmacia Animal Health, Kalamazoo, MI 49001

Corresponding author:
John R. Chenault; e-mail:
John.R.Chenault{at}Pharmacia.com.

Milk from pregnant cows contains concentrations of progesterone (P4) considered safe for human consumption. The objective of this study was to determine if concentrations of P4 in milk during administration of an intravaginal progesterone insert (CIDR insert) are less than concentrations of P4 in milk associated with pregnancy. Results have implications for human use of milk from cows receiving CIDR inserts. Holstein cows (N = 64; > 40 and < 150 d after calving) were administered 25 mg of PGF₂ i.m. (study d 0) and 20 cows detected in estrus from 2 to 4 d later were assigned randomly to either control (N = 10; no further treatment) or CIDR insert (N = 10; 1.38 g of P4) inserted on study d 17 (14 ± 1 d after estrus) and removed 7 d later. Composite milk samples were collected contemporaneously from each of the 20 estrous cycling cows and from 10 pregnant cows ( 60 and 220 d of gestation) twice daily from study d 17 to 27. Concentrations of P4 in de-fatted milk samples were quantified using a validated radioimmunoassay. Mean logs of areas under the curve of concentrations of P4 from the afternoon on study d 17 through the afternoon on study d 27 were 3.05 ng day/ml for control, 3.33 ng day/ml for CIDR insert, and 3.81 ng day/ml for pregnant cows. Therefore, increased P4 due to pregnancy was 0.76 ng day/ml (3.81 - 3.05), whereas the increase in P4 due to CIDR insert was only 0.28 ng day/ml (3.33 - 3.05). Applying a 95% confidence interval to 0.28 ng day/ml provided an upper value of 0.70 ng day/ml, lower than the increase due to pregnancy. Because milk from pregnant cows is considered safe for human consumption, it follows that milk from cows administered CIDR inserts should also be considered safe, based on concentrations of P4.

Key Words: intravaginal progesterone insert • concentrations of progesterone in milk • dairy cow

Abbreviation key: AUC = area under the curve, CIDR insert = EAZI-BREED CIDR Cattle Insert, CIDR B insert = EAZI-BREED CIDR B Cattle Insert, DPC = Diagnostic Products Corporation, LOQ = limit of quantification, P4 = progesterone, QC = quality control

This article has been cited by other articles:

				S. Z. El-Zarkouny and J. S. Stevenson Resynchronizing Estrus with Progesterone or Progesterone Plus Estrogen in Cows of Unknown Pregnancy Status J Dairy Sci, October 1, 2004; 87(10): 3306 - 3321. [Abstract] [Full Text] [PDF]