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ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Publications at this Location » Publication #138124
Title: ESTROUS CHARACTERISTICS AND PREGNANCY RATES OF BEEF HEIFERS ADMINISTERED TWO SYNCHRONIZATION PROTOCOLS

Author
item ROGERS, C - NEW MEXICO STATE UNIV
item DRUMMOND, T - NEW MEXICO STATE UNIV
item FLORES, R - SOUTHWEST BIOLABS
item MATHIS`, C - NEW MEXICO STATE UNIV
item LOOPER, MICHAEL - 6227-05-00

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2002
Publication Date: 2/1/2003
Citation: ROGERS, C.A., DRUMMOND, T.W., FLORES, R., MATHIS`, C.P., LOOPER, M.L. 2003. ESTROUS CHARACTERISTICS AND PREGNANCY RATES OF BEEF HEIFERS ADMINISTERED TWO SYNCHRONIZATION PROTOCOLS. PROFESSIONAL ANIMAL SCIENTIST. 19(1):19.

Interpretive Summary: Synchronization can simplify reproductive management, reduce the necessity for visual estrous detection, and improve the success of an artificial insemination program in cattle. Beef heifers were treated with either gonadotropin-releasing hormone (GnRH) 7 days before treatment with prostaglandin F2alpha (PGF2alpha) or with two administrations of PGF2alpha 14 days apart. Intensity of estrus was increased in heifers administered PGF2alpha 14 d apart compared with heifers administered GnRH 7 d before treatment with PGF2alpha; however synchronization and pregnancy rates were not influenced by synchronization protocol. This information is of interest to producers that utilize synchronization protocols, and extension personnel and agricultural professionals who advise producers on reproductive management.

Technical Abstract: Two estrous synchronization protocols were used to determine their effect on estrous characteristics, synchronization rates, and pregnancy rates in nulliparous beef heifers on a commercial cow/calf operation in western New Mexico. Fifty-three Angus and Angus x Hereford heifers were sorted by age and BW to compare heifers treated with gonadotropin-releasing hormone (GnRH) 7 d before treatment with prostaglandin F2alpha (PGF2alpha; SelectSynch; SS; n = 26) and heifers treated with two administrations of PGF2alpha 14 d apart (Targeted Breeding; TB; n = 27). An androgenized cow fitted with a chin-ball marker was placed in each pen of heifers, and a HeatWatch (HW) transmitter was attached to each heifer to monitor estrous characteristics. Heifers were artificially inseminated after estrus was determined by HW. Number of standing events tended (P = 0.12) to be increased in TB heifers than SS heifers (54.4 ± 7.4 and 37.5 ± 7.7, respectively). Duration of estrus was increased (P < 0.05) in TB heifers (16.0 ± 1.3 h vs. 11.6 ± 1.3 h). However, overall synchronization and pregnancy rates were similar (P > 0.10) between protocols. Androgenized cows identified 53% of the estruses detected by HW. When utilizing synchronization protocols, radiotelemetric estrous detection systems may identify more estrus heifers than androgenized cows. Intensity of estrus was increased in heifers administered PGF2alpha 14 d apart compared with heifers administered GnRH 7 d before treatment with PGF2alpha; however synchronization and pregnancy rates were not influenced by synchronization protocol.