OVULATION CONTROL IN CATTLE WITH PROGESTERONE INTRAVAGINAL DEVICE (PRID) AND GONADOTROPIN RELEASING HORMONE (GnRH)

Abstract

A technique for chronic application of progesterone intravaginally in cattle is described. When used in conjunction with gonadotropin releasing hormone (GnRH), synchronized ovulation is achieved for timed artificial insemination. Progesterone is released from a silicone rubber matrix attached to a stainless steel spiral. Plasma progesterone concentration reaches luteal phase levels shortly after insertion and falls to I to 3 ng per ml of plasma by day 21 when the device is removed. An intramuscular injection of IOO vg of GnRH 28 to 30 hours after device removal induces an LH surge comparable to the normal preovulatory LH surge. Conception rates in dry cows and heifers have been comparable to controls.