Randomised controlled trial of the effect of concentration of progesterone before artificial insemination on fertility in ovulatory and anovulatory Bos indicus cattle.

Abstract

OBJECTIVE: To investigate the effect of concentration of progesterone (P4) before artificial insemination (AI) on fertility in ovulatory or anovulatory Bos indicus cattle. DESIGN: Randomised control study METHODS: The study included 162 heifers and 96 lactating cows. On days -10 to -12, animals were examined using transrectal ultrasound, administered PG and examined for a corpus luteum (CL). Those with a CL were allocated to Experiment 1. On day 0 they were administered an intravaginal progesterone-releasing device (IVD) containing progesterone (P4) (0.78 g), oestrodiol benzoate (ODB) and either saline or PG to induce high and low circulating P4 concentrations, respectively. Those without a ..