|Lucy, M - UNIV. OF MISSOURI|
|Billings, H - RUTGERS UNIVERSITY|
|Butler, W - CORNELL UNIVERSITY|
|Ehnis, L - UNIV. OF NEBRASKA|
|Fields, M - UNIV. OF FLORIDA|
|Kesler, D - UNIV. OF ILLINOIS|
|Kinder, J - UNIV. OF NEBRASKA|
|Mattos, R - UNIV. OF FLORIDA|
|Thatcher, W - UNIV. OF FLORIDA|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2000
Publication Date: April 1, 2001
Citation: LUCY, M.C., BILLINGS, H.J., BUTLER, W.R., EHNIS, L.R., FIELDS, M.J., KESLER, D.J., KINDER, J.E., MATTOS, R.C., SHORT, R., THATCHER, W.W. EFFICACY OF AN INTRAVAGINAL PROGESTERONE INSERT AND AN INJECTION OF PGF2ALPFOR SYNCHRONIZING ESTRUS AND SHORTENING THE INTERVAL TO PREGNANCY IN POSTPARTUM BEEF COWS, PERIPUBERTAL BEEF HEIFERS, AND DAIRY HEIFERS. JOURNAL OF ANIMAL SCIENCE. 79:982-995. 2001. Interpretive Summary: Estrous synchronization is an important tool for increasing the rate of implementation of artificial insemination in beef and dairy herds. Methods for estrous synchronization should be relatively simple to employ and should be robust so that they can be applied under a variety of management conditions. The CIDR+PGF2alpha program met these criteria as it was effective at multiple locations in the United States that employed cattle of different genetic backgrounds and management conditions. The efficacy of the CIDR in these studies suggests that the insert will be a reliable option for estrous synchronization in cattle when used in conjunction with an injection of PG.
Technical Abstract: Control (C) cattle were not treated and treated cattle were administered PGF2alpha (PG) or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with PG on d 6. The treatments were applied in 1 of 3 experiments that involved postpartum beef cows (Exp. 1; n=851), beef heifers (Exp. 2; n=724), and dairy heifers (Exp. 3; n=260). In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+PG-treated cows compared with PG-treated or C cows (15, 33, and 59% for C, PG, and CIDR+PG, resp.; (P<0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for C, PG, and CIDR+PG, resp.; P<0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+PG (50, 55, and 58% for C, PG, and CIDR+PG, resp., P<0.10). Improvements in estrus and pregnancy rates after CIDR+PG were also observed in beef heifers (Exp. 2). Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The PG and CIDR+PG treatments were evaluated in dairy heifers (Exp. 3). The CIDR+PG-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared to the PG-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+PG compared with PG- treated heifers.