Abstract
Our objectives were to determine whether a fixed-time artificial insemination (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus and whether inclusion of a CIDR (a vaginal insert containing progesterone) in protocols using gonadotropin-releasing hormone (GnRH) and prostaglandin F2α (PGF) would enhance fertility. Postpartum suckled beef cows (n = 2,630) from 14 locations were assigned randomly to each of five estrus-synchronization protocols using PGF with GnRH and(or) a CIDR. Protocols were Control, CO-Synch, COSynch+CIDR, Hybrid-Synch, and HybridSynch+CIDR. The percentage of cows cycling at the initiation of estrus synchronization was 66.8%, the percentage of cycling cows ranging from 38 to 90% among locations. Overall pregnancy among locations ranged from 39% to 67%. Pregnancy rates were greatest for the Hybrid-Synch+CIDR (57.9%) treatment, although not significantly different from the CO-Synch+CIDR (53.6%) and Hybrid-Synch (53.0%) treatments, but greater than the Control (52.3%) and CO-Synch (43.4%), which yielded the poorest pregnancy rates. Overall, the Hybrid-Synch+CIDR protocol (AI after detected estrus for 3 days, and then a clean-up TAI) achieved the greatest pregnancy rates, but CO-Synch+CIDR is a reliable, fixed-time AI protocol that gives producers the option to eliminate detection of estrus.
Highlights
Synchronization of estrus shortens the calving season, increases calf uniformity, and enhances the possibilities for using artificial insemination (AI)
Our objectives were to determine whether a fixed-time artificial insemination (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus and whether inclusion of a CIDR in protocols using gonadotropin-releasing hormone (GnRH) and prostaglandin F2α(PGF) would enhance fertility
The percentage of cows cycling at the initiation of estrus synchronization was 66.8%, the percentage of cycling cows ranging from 38 to 90% among locations
Summary
Synchronization of estrus shortens the calving season, increases calf uniformity, and enhances the possibilities for using artificial insemination (AI). The EAZI-BREED CIDR® (CIDR; Pharmacia Animal Health, Kalamazoo, MI) was recently approved by the U.S Food and Drug Administration for synchronizing estrus in beef cows. Nal insert that contains 1.38 g of progesterone, which is gradually released over a period of days, and it can be used effectively with prostaglandin F2α (PGF) with or without gonadotropin-releasing hormone (GnRH) to synchronize estrus or ovulation in beef cows. The objectives of this study were to determine whether: 1) a TAI protocol could yield pregnancy rates similar to a protocol requiring detection of estrus; and 2) inclusion of a CIDR to GnRH and PGF-based protocols would enhance fertility.
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