Comparison of three CIDR-based fixed-time AI protocols in beef heifers1

Abstract

Several effective fixed-time AI (FTAI) protocols have been developed to facilitate AI in beef heifers that circumvent the need for estrus detection. Among these are the 5-d CO-Synch + controlled intravaginal progesterone insert (CIDR) protocol (5dCO), PGF2α (PG) 6-d CIDR protocol (PG-6dCIDR), and 14-d CIDR-PG protocol (14dCIDR-PG). Although each of these protocols varies in duration and approach to synchronizing estrus and ovulation, each has been reported as an effective method to facilitate FTAI in beef heifers. Therefore, the objective of this study was to compare FTAI pregnancy rates in beef heifers synchronized with these 3 CIDR-based protocols. Virgin beef heifers (n = 801) at 4 locations were synchronized with 1 of 3 protocols: 1) 5dCO, an injection of GnRH (100 μg) and insertion of a CIDR on d -5, PG (25 mg) and CIDR removal on d 0 with a second injection of PG (>4 h after CIDR removal) on d 0 and FTAI at 72 h after CIDR removal, 2) PG-6dCIDR, PG (25 mg) on d -9, GnRH (100 μg) and insertion of a CIDR on d -6, PG and CIDR removal on d 0, and FTAI at 66 h after CIDR removal, or 3) 14dCIDR-PG, a 14-d CIDR insert from d -30 to -16, PG (25 mg) on d 0, and FTAI at 66 h after PG. All heifers received an injection of GnRH (100 μg) concurrent with FTAI. Timing of treatment initiation was offset to allow all heifers to receive FTAI concomitantly and at random. Pregnancy success was determined between 35 and 40 d after FTAI by transrectal ultrasonography. Blood samples were collected before the beginning of each protocol and at the initiation of each protocol to determine estrous cycling status (77%). Data were analyzed using the GLIMMIX procedures of SAS. As expected, because of the duration of protocols, fewer heifers in the 14dCIDR-PG treatment were pubertal at initiation of synchronization than in the 5dCO (P < 0.05) and PG-6dCIDR (P = 0.10) treatments. Fixed-time AI pregnancy success did not differ between treatments (P = 0.14; 62.6%, 56.9%, and 53.3% for 5dCO, PG-6dCIDR, and 14dCIDR-PG, respectively). However, heifers that had reached puberty by initiation of synchronization had greater (P < 0.01) pregnancy success compared to heifers that were prepubertal (60.7% and 47.3%, respectively). In summary, all 3 protocols had similar FTAI pregnancy success, and puberty status had the greatest impact on pregnancy success.

Effects on Synchronization and Reproductive Efficiency of Delaying the Removal of the Intravaginal Progesterone Device by 24 h in the 5d Co-Synch Protocol in Heifers

“…Similarly, the age of beef heifers in the second part of this study did not influence the probability of pregnancy after FTAI. For adequately developed beef heifers, reaching puberty before FTAI may be even more important for fertility than age [23]. Age may not have influenced conception rate in our study because the heifers (21.7 ± 3.54 months old) had reached puberty and had adequate body condition.…”

“…Such pre-synchronization has been associated with higher CR in dairy heifers [21], higher fertility rate after FTAI in multiparous beef cattle [20], and greater ovarian synchronization in beef heifers [22]. In beef heifers, however, another study did not observe different CRs between the 5d Co-synch 72-h protocol and a prostaglandin 6d-IPD protocol, consisting of prostaglandin (25 mg) on Day −9, GnRH (100 µg) and IPD insertion on Day −6, PG and IPD removal on Day 0, and FTAI at 66 h after IPD removal [23]. Unlike the prostaglandin 6d-IPD protocol, the modified protocol in the present study did not include pre-synchronization with prostaglandin.…”

Effects of delaying the removal of the intravaginal progesterone device by 24 h in the 5d Co-synch protocol in heifers

“…Similarly, the age of beef heifers in the second part of this study did not in uence the probability of pregnancy after FTAI. For adequately developed beef heifers, reaching puberty before FTAI may be even more important for fertility than age [42]. Age may not have in uenced conception rate in our study because the heifers (21.7 ± 3.54 months old) had reached puberty and had adequate body condition.…”

“…Such pre-synchronization has been associated with higher CR in dairy heifers [40], higher fertility rate after FTAI in multiparous beef cattle [39], and greater ovarian synchronization in beef heifers [41]. In beef heifers, however, another study did not observe different CRs between the 5d Co-synch 72 h protocol and a prostaglandin 6d-IPD protocol, consisting of prostaglandin (25 mg) on Day − 9, GnRH (100 µg) and IPD insertion on Day − 6, PG and IPD removal on Day 0, and FTAI at 66 h after IPD removal [42]. Unlike the prostaglandin 6d-IPD protocol, the modi ed protocol in the present study did not include pre-synchronization with prostaglandin.…”

Manipulation of Fertility in Crossbred Dairy Cattle Using Controlled Internal Drug Release Device Combined With Prostaglandin and Equine Chorionic Gonadotrophin

“…Promising developments have been shown by reducing the time of keeping CIDR devices in the vagina to 4 [23] or 5 days [15,24], although estrus response and conception rates are not consistent even after the use of the standard 7-day CIDR regime [3,25,26] which could be due to environmental, management, breed and other factors. Yet, a recent report showed a similar pregnancy success when CIDR was maintained for 5 days, 6 days and 14 days in heifers [27]. Moreover, another recent study that compared between 7 and 9 days CIDR inserts on estrus response and fertility in dairy cattle has shown a similar effect between the two protocols [28].…”