| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Dairy Science and
2 Department of Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061
Corresponding author: R. L. Nebel; e-mail: rnebel{at}vt.edu.
Reproductive performance of dairy heifers was compared for each of 2 synchronization protocols: The first group of 54 heifers was synchronized using intravaginal progesterone inserts (CIDR) plus estradiol cypionate (ECP) on d 0, PGF2
on d 7, and ECP again on d 8 (CIDR-ECP); a second group of 56 heifers was synchronized using CIDR and ECP on d 0, PGF2 on d 7, and GnRH on d 9 (CIDR-GnRH). All heifers received timed artificial insemination (TAI) at 48, 56, or 72 h after CIDR removal on d 7. Pregnancy diagnosis was conducted by ultrasonography 32 ± 1 d post AI to confirm pregnancy and at 60 ± 1 d post AI to determine embryo survival. Ovaries were monitored by ultrasonography daily from d 0 to 7 and twice daily from d 8 to ovulation to examine emergence of a new wave of follicles, size of the ovulatory follicle, and timing of ovulation on 15 heifers per protocol. New follicular development was detected 3.7 ± 0.2 d after CIDR insertion. Heifers receiving CIDR-ECP had a shorter interval from CIDR removal to ovulation than heifers receiving CIDR-GnRH (63.8 ± 3.0 vs. 71.6 ± 2.3 h, respectively); however, ovulation occurred 39.8 ± 3.0 h after ECP or 23.6 ± 2.3 h after GnRH. Diameters of ovulatory follicles did not differ between treatments. Overall pregnancy rate for synchronized heifers was 60.1%, and embryo survival was 98%. Pregnancy rate for heifers synchronized with CIDR-ECP was 63.0% and similar to that in heifers synchronized with CIDR-GnRH (57.1%). Pregnancy rate was affected by time of AI for heifers synchronized using CIDR-ECP but not for those synchronized with CIDR-GnRH. Heifers in the CIDR-ECP group that were inseminated 56 h after CIDR removal had a higher pregnancy rate (81.0%) compared with heifers inseminated 48 (66.7%) or 72 h (50.0%) after CIDR removal. Either ECP or GnRH used in a CIDR-based TAI program in dairy heifers can achieve acceptable reproductive performance.
Key Words: intravaginal progesterone insert • timed artificial insemination • reproductive performance • dairy heifer
Abbreviation key: CIDR = intravaginal progesterone insert, E2 = estrogen, ECP = estradiol cypionate, P4 = progesterone, PR = pregnancy rate, TAI = timed artificial insemination
This article has been cited by other articles:
|
|
 |
|
  D. J. Ambrose, D. G. V. Emmanuel, M. G. Colazo, and J. P. Kastelic Short Communication: Pregnancy Rates to Timed Artificial Insemination in Holstein Heifers Given Prostaglandin F2{alpha} Twenty-Four Hours Before or Concurrent with Removal of an Intravaginal Progesterone-Releasing Insert J Dairy Sci, July 1, 2008; 91(7): 2678 - 2683. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Rivera, R. A. Sterry, and P. M. Fricke Presynchronization with gonadotropin-releasing hormone does not improve fertility in holstein heifers. J Dairy Sci, October 1, 2006; 89(10): 3810 - 3816. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Rivera, H. Lopez, and P. M. Fricke Use of Intravaginal Progesterone-Releasing Inserts in a Synchronization Protocol before Timed AI and for Synchronizing Return to Estrus in Holstein Heifers J Dairy Sci, March 1, 2005; 88(3): 957 - 968. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
