Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2α, and progesterone1

Abstract

We determined whether a fixed-time AI (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus, or estrous detection plus TAI, and whether adding a controlled internal device release (CIDR) to GnRH-based protocols would enhance fertility. Estrus was synchronized in 2,598 suckled beef cows at 14 locations, and AI was preceded by 1 of 5 treatments: 1) a CIDR for 7 d with 25 mg of PG F(2alpha) (PGF) at CIDR removal, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received 100 mug of GnRH and TAI at 84 h (control; n = 506); 2) GnRH administration, followed in 7 d with PGF, followed in 60 h by a second injection of GnRH and TAI (CO-Synch; n = 548); 3) CO-Synch plus a CIDR during the 7 d between the first injection of GnRH and PGF (CO-Synch + CIDR; n = 539); 4) GnRH administration, followed in 7 d with PGF, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received GnRH and TAI at 84 h (Select Synch & TAI; n = 507); and 5) Select Synch & TAI plus a CIDR during the 7 d between the first injection of GnRH and PGF (Select Synch + CIDR & TAI; n = 498). Blood samples were collected (d -17 and -7, relative to PGF) to determine estrous cycle status. For the control, Select Synch & TAI, and Select Synch + CIDR & TAI treatments, a minimum of twice daily observations for estrus began on d 0 and continued for at least 72 h. Inseminations were performed using the AM/PM rule. Pregnancy was diagnosed by transrectal ultrasonography. Percentage of cows cycling at the initiation of treatments was 66%. Pregnancy rates (proportion of cows pregnant to AI of all cows synchronized during the synchronization period) among locations across treatments ranged from 37% to 67%. Pregnancy rates were greater (P < 0.05) for the Select Synch + CIDR & TAI (58%), CO-Synch + CIDR (54%), Select Synch & TAI (53%), or control (53%) treatments than the CO-Synch (44%) treatment. Among the 3 protocols in which estrus was detected, conception rates (proportion of cows that became pregnant to AI of those exhibiting estrus during the synchronization period) were greater (P < 0.05) for Select Synch & TAI (70%; 217 of 309) and Select Synch + CIDR & TAI (67%; 230 of 345) cows than for control cows (61%; 197 of 325). We conclude that the CO-Synch + CIDR protocol yielded similar pregnancy rates to estrous detection protocols and is a reliable TAI protocol that eliminates detection of estrus when inseminating beef cows.

Altered progesterone concentrations by hormonal manipulations before a fixed-time artificial insemination CO-Synch + CIDR program in suckled beef cows

“…1). 2 Median days between calving and day of timed AI. 3 Body condition score assessed 1 wk before CIDR insertion.…”

“…Several ovulation synchronization protocols that use exogenous GnRH at the time of insertion of a progesteroneimpregnated intravaginal controlled internal drug release (CIDR) insert have been developed [1,2]. Beef herds that have >50% anestrous cows at the start of the breeding season may benefit from protocols that promote ovulation in response to GnRH before initiating a timed AI (TAI) program.…”

Fixed-time AI pregnancy rate following insemination with frozen-thawed or fresh-extended semen in progesterone supplemented CO-Synch protocol in beef cows

“…With this trend, there is an opportunity to investigate the possibility of maintaining or improving the reproductive outcome in commercial beef operations using fresh0extended semen with low sperm numbers per insemination, instead of frozen-thawed semen with high sperm numbers. estrus in anestrous cows [6][7][8]. Our previous CO-Synch-CIDR study, with an interval of 64 h between the PGF2 α and the second GnRH treatment, resulted in an acceptable fixed-time AI pregnancy rate [9].…”

Effect of preovulatory follicle maturity on pregnancy establishment in cattle: the role ofoocyte competence and the maternal environment

“…Animals that have not expressed estrus by the time of FTAI require an injection of GnRH or estradiol to induce a preovulatory gonadotropin surge and ovulation so that all animals can be inseminated at the same time. Females that exhibit estrus prior to or at the time of FTAI normally have a spontaneous gonadotropin surge and experience higher pregnancy rates compared to those that fail to exhibit estrus (Perry et al, 2005;Larson et al, 2006). Therefore, a challenge with FTAI is to manipulate the estrous cycle or the induction of ovulation such that the follicular microenvironment is optimal for acquisition of oocyte competence and programming the maternal environment for the establishment and maintenance of pregnancy.…”