title: Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone.
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.
authors.affiliation: North Central Research and Outreach Center, University of Minnesota, Grand Rapids, 55744, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Larson
authors.forename: G C
authors.initials: GC
authors.lastname: Lamb
authors.forename: J S
authors.initials: JS
authors.lastname: Stevenson
authors.forename: S K
authors.initials: SK
authors.lastname: Johnson
authors.forename: M L
authors.initials: ML
authors.lastname: Day
authors.forename: T W
authors.initials: TW
authors.lastname: Geary
authors.forename: D J
authors.initials: DJ
authors.lastname: Kesler
authors.forename: J M
authors.initials: JM
authors.lastname: DeJarnette
authors.forename: F N
authors.initials: FN
authors.lastname: Schrick
authors.forename: A
authors.initials: A
authors.lastname: DiCostanzo
authors.forename: J D
authors.initials: JD
authors.lastname: Arseneau
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004972:Estrus Detection; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D005298:Fertility / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation / Q000502:physiology; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D012744:Sex Ratio; D013997:Time Factors
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost