Insertion of a Used CIDR on Day 3 to 5 Post-Insemination in Heifers to Improve Pregnancy Rate

The study was designed to determine if increasing progesterone (P4) post-insemination could improve pregnancy rates. Beef heifers were randomly allotted to receive a controlled internal drug, P4, releasing device (CIDR) on day 3 to 5 or serve as a control. In Replicate 1, significantly more treated heifers became pregnant than control heifers (P \u3c 0.05); however, there was no difference (P \u3e 0.05) in the pregnancy rate in Replicate 2. Among control heifers in Replicate 2, pregnant heifers had significantly higher (P \u3c 0.05) plasma P4 on day 4 and 5 compared with non-pregnant heifers