Comparison of short-term progestin-based protocols to synchronize estrus and ovulation in postpartum beef cows.
Two experiments evaluated short-term controlled internal drug release (CIDR) insert-based protocols to synchronize estrus and ovulation and compare differences in their potential to facilitate fixed-time AI (FTAI) in postpartum beef cows. Experiment 1 was designed to compare the 7- and 5-d Select Synch + CIDR protocols on the basis of timing and synchrony of estrus after treatment. Cows assigned to the 7-d protocol (n = 59) received GnRH [100 microg intramuscularly (i.m.)] and CIDR inserts (1.38 g of progesterone) on d 0 and PGF(2alpha) (25 mg i.m.) and CIDR removal on d 7. Cows assigned to the 5-d protocol (n = 58) received GnRH and CIDR inserts on d 2, PGF(2alpha) and CIDR removal on d 7, and a second injection of PGF(2alpha) 12 h after CIDR removal. Estrus detection and AI were performed for cows assigned to each protocol during the 144-h synchronized period. There was no difference in estrous response (P = 0.85), interval to estrus (P = 0.09), or variance for interval to estrus (P = 0.75) between treatments, nor were there differences in synchronized conception or pregnancy rates resulting from AI (P = 0.85, P = 0.91, respectively). Experiment 2 was designed to compare pregnancy rates resulting from FTAI after administration of the 7- and 5-d CO-Synch + CIDR protocols. Both treatments were administered the same as in Exp. 1; however, cows assigned to the 7-d protocol were inseminated 66 h after PGF(2alpha) and CIDR removal, and cows assigned to the 5-d protocol were inseminated 72 h after the first PGF(2alpha) injection. Cows assigned to both protocols were administered GnRH (100 microg i.m.) at AI. There was no effect of treatment (P = 0.85), technician (P = 0.20), or sire (P = 0.25) on pregnancy rates resulting from FTAI. Given these observations, the 5-d protocol provides an effective alternative to the 7-d protocol for use in facilitating FTAI; however, beef producers must carefully consider the increased labor and treatment costs associated with the 5-d protocol.
Wilson
D J
DJ
Division of Animal Science, S132 ASRC, University of Missouri, Columbia 65211, USA.
Mallory
D A
DA
Busch
D C
DC
Leitman
N R
NR
Haden
J K
JK
Schafer
D J
DJ
Ellersieck
M R
MR
Smith
M F
MF
Patterson
D J
DJ
D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000662:veterinary; D016014:Linear Models; D008297:Male; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage; D011897:Random Allocation
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost