Document Detail

Comparison of progestin-based protocols to synchronize estrus and ovulation before fixed-time artificial insemination in postpartum beef cows.
MedLine Citation:
PMID:  17400969     Owner:  NLM     Status:  MEDLINE    
This experiment was designed to compare pregnancy rates in postpartum beef cows resulting from fixed-time AI (FTAI) after treatment with 1 of 2 protocols to synchronize estrus and ovulation. Cross-bred, suckled beef cows (n = 650) at 4 locations (n = 210; n = 158; n = 88; and n = 194) were assigned within a location to 1 of 2 protocols within age group by days postpartum and BCS. Cows assigned to the melengestrol acetate (MGA) Select treatment (MGA Select; n = 327) were fed MGA (0.5 mg x head(-1) x d(-1)) for 14 d, GnRH (100 microg of Cystorelin i.m.) was injected on d 26, and prostaglandin F2alpha (PG; 25 mg of Lutalyse i.m.) was injected on d 33. Cows assigned to the CO-Synch + controlled internal drug release (CIDR) protocol (CO-Synch + CIDR; n = 323) were fed a carrier for 14 d, were injected with GnRH and equipped with an EAZI-BREED CIDR insert (1.38 g of progesterone, Pfizer Animal Health, New York, NY) 12 d after carrier removal, and PG (25 mg of Lutalyse i.m.) was injected and the CIDR were removed on d 33. Fixed-time AI was performed at 72 or 66 h after PG for the MGA Select or CO-Synch + CIDR groups, respectively. All cows were injected with GnRH (100 microg of Cystorelin i.m.) at the time of insemination. Blood samples were collected 8 and 1 d before the beginning of MGA or carrier to determine estrous cyclicity status of the cows (estrous cycling vs. anestrus) before treatment [progesterone > or = 0.5 ng/mL (MGA Select, 185/327, 57%; CO-Synch + CIDR, 177/323, 55%); P = 0.65]. There was no difference (P = 0.20) in pregnancy rate to FTAI between treatments (MGA Select, 201/327, 61%; CO-Synch + CIDR, 214/323, 66%). There was also no difference (P = 0.25) between treatments in final pregnancy rate at the end of the breeding period (MGA Select, 305/327, 93%; CO-Synch + CIDR, 308/323, 95%). These data indicate that pregnancy rates to FTAI were comparable after administration of the MGA Select or CO-Synch + CIDR protocols. Both protocols provide opportunities for beef producers to utilize AI and potentially eliminate the need to detect estrus.
D J Schafer; J F Bader; J P Meyer; J K Haden; M R Ellersieck; M C Lucy; M F Smith; D J Patterson
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2007-03-30
Journal Detail:
Title:  Journal of animal science     Volume:  85     ISSN:  1525-3163     ISO Abbreviation:  J. Anim. Sci.     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-07-16     Completed Date:  2007-10-16     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1940-5     Citation Subset:  IM    
Division of Animal Sciences, University of Missouri, Columbia 65211, USA.
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MeSH Terms
Abortion, Veterinary
Administration, Oral
Animal Husbandry / methods*
Cattle / physiology*
Dinoprost / administration & dosage,  analogs & derivatives,  pharmacology
Drug Implants
Estrus Synchronization / drug effects,  methods*
Fertility Agents, Female / administration & dosage,  pharmacology*
Gonadotropin-Releasing Hormone / administration & dosage
Insemination, Artificial / veterinary
Melengestrol Acetate / administration & dosage
Ovulation / drug effects*
Postpartum Period
Pregnancy Rate*
Progesterone / administration & dosage
Reg. No./Substance:
0/Drug Implants; 0/Fertility Agents, Female; 2919-66-6/Melengestrol Acetate; 33515-09-2/Gonadotropin-Releasing Hormone; 38562-01-5/dinoprost tromethamine; 551-11-1/Dinoprost; 57-83-0/Progesterone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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