Document Detail

Control of the estrous cycle to improve fertility for fixed-time artificial insemination in beef cattle: a review.
MedLine Citation:
PMID:  19783709     Owner:  NLM     Status:  MEDLINE    
Early estrus-synchronization protocols focused on regressing the corpus luteum (CL) with an injection of PGF(2alpha) followed by detection of estrus or involved the use of exogenous progestins that prevent estrus from occurring. Later, protocols combining the use of PGF(2alpha) and exogenous progestins were developed. Gonadotropin-releasing hormone was utilized to control follicular waves, synchronize ovulation, or to luteinize large dominant follicles. Our research aimed to develop reliable protocols that 1) relied solely on fixed-timed AI (TAI); 2) required a maximum of 3 animal handlings, and 3) were successful in estrous-cycling and noncycling females. In cows, insertion of an intravaginal progesterone insert during the 7-d interval between the initial GnRH and PGF(2alpha) injections enhanced pregnancy rates by 9 to 10%. In a multi-location study, a TAI protocol yielded pregnancy rates similar to a protocol involving detection of estrus plus a fixed-time clean-up AI for females not detected in estrus (54 vs. 58%, respectively, for cows and 53 vs. 57%, respectively, for heifers). Initiation of estrous cycles in noncycling cows is likely the primary manner in which beef producers may improve fertility in response to estrus synchronization and TAI protocols. Treatment of noncycling females with progesterone and GnRH increases the percentage of cycling females and improves fertility to a TAI, but inducing cyclicity with hCG failed to enhance fertility in TAI protocols. Supplementing progesterone after TAI failed to increase pregnancy rates in beef cattle. In contrast, administration of hCG 7 d after TAI induced an accessory CL, increased progesterone, and tended to enhance pregnancy rates. Development of TAI protocols that reduce the hassle factors associated with ovulation synchronization and AI provide cattle producers efficient and effective tools for capturing selective genetic traits of economic consequences. Location variables, however, which may include differences in pasture and diet, breed composition, body condition, postpartum interval, climate, and geographic location, affect the success of TAI protocols.
G C Lamb; C R Dahlen; J E Larson; G Marquezini; J S Stevenson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review     Date:  2009-09-25
Journal Detail:
Title:  Journal of animal science     Volume:  88     ISSN:  1525-3163     ISO Abbreviation:  J. Anim. Sci.     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-04-20     Completed Date:  2010-07-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  E181-92     Citation Subset:  IM    
North Florida Research and Education Center, University of Florida, Marianna, FL 32446, USA.
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MeSH Terms
Animal Husbandry / methods
Cattle / physiology*
Estrus Detection / methods
Estrus Synchronization / methods*
Fertility / physiology
Gonadotropin-Releasing Hormone / pharmacology
Insemination, Artificial / methods,  veterinary*
Progesterone / pharmacology
Reg. No./Substance:
33515-09-2/Gonadotropin-Releasing Hormone; 57-83-0/Progesterone

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

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