Laboratory 3

  1. Introduction
  2. Review: Progesterone in cattle
    1. Normal cycle
    2. Pregnancy
  3. Measurement of Milk Progesterone





Review: Progesterone Levels in Cattle

Progesterone is a steroid hormone produced by the corpus luteum (CL) on the ovary which forms after ovulation of the oocyte. Progesterone targets uterine epithelium, mammary tissue, myometrium and hypothalmus causing endometrial secretion, inhibition of GnRH release and promotes maintenance of pregnancy.

The level of progesterone in the serum and milk reflects the activity of the CL on the ovary. The level of progesterone increases for the first 4 to 6 days following ovulation. Maximum levels are reached between days 10-17.

If the cow becomes pregnant, the CL is maintained and high levels of progesterone are produced which helps to maintain pregnancy. If the cow does not become pregnant, the CL begins to regress and the level of progesterone sharply decreases on days 18 or 19 and allowing the cow to return to estrus on day 21-23.

normal cyclepregnant cycle