PERIPHERAL PLASMA CONCENTRATIONS OF PROGESTERONE, OESTRADIOL-17β AND LUTEINIZING HORMONE AROUND OESTRUS IN THE COW

Abstract

I.N.R.A.-Laboratoire de Physiologie de la Reproduction, Nouzilly, 37380 Monnaie, France (Received 29th May 1974) The concentrations of a number of reproductive hormones found in the peripheral plasma of the cow around the time of oestrus have been measured by numerous authors: plasma concentrations of progesterone throughout the oestrous cycle (Stabenfeldt, Ewing & McDonald, 1969), LH (Schams & Karg, 1969), oestrogen and progesterone (Henricks, Dickey & Hill, 1971) and LH and progesterone (Henricks, Dickey & Niswender, 1970). These and other reports have paid little attention to the precise onset and duration of oestrus, behaviour being checked at various intervals (usually two or three times a day) before the expected onset. To obtain a more precise pattern of hormone concentrations around oestrus, we have measured simultaneously LH, oestradiol-17β and progesterone in samples of plasma taken at 2-hr intervals from cows over a period of 5 days. The cows were maintained with a