Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2002
Publication Date: 4/1/2002
Citation: FUNSTON, R.N., ANSOTEGUI, R.P., LIPSEY, R.J., GEARY, T.W. FEEDING MELENGESTEROL ACETATE (MGA) SEVEN DAYS PRIOR TO THE SELECT SYNCH ESTROUS SYNCHRONIZATION PROTOCAL RESULTS IN EQUAL PREGNANCY RATES COMPARED TO THE CONVENTIONAL MGA/17 DAYS PROSTAGLANDIN SYNC PROTOCOL IN BEEF HEIFERS. THERIOGENOLOGY. 2002. v. 57. p. 1485-1491. Interpretive Summary: Feeding MGA 7 d before the Select Synch protocol provided equal synchronization and pregnancy rates as the traditional MGA/PGF protocol in beef heifers. This may be a viable synchronization program for producers who want a shorter synchronization program or a program that requires less days of feeding MGA than the traditional MGA/PGF program.
Technical Abstract: The objective of this study was to evaluate synchronization, conception, and pregnancy rates of yearling beef heifers synchronized with either the Select Synch protocol preceded by 7 d of MGA feeding (MGA/Select Synch) or the traditional MGA/PGF protocol. Heifers in the MGA/Select Synch group (n=402) were fed MGA (0.5mg/hd/d) for 7 d, received an injection of GnRH (100 mcg) the day following the last MGA feeding and an injection of PGF (25 mg) 7 d after GnRH. Heifers in the MGA/PGF group (n=394) received MGA (0.5mg/hd/d) for 14 d followed 17 d later by an injection of PGF (25 mg). Synchronization rates tended (P=0.08) to be higher for the MGA/Select Synch (82%) compared to the MGA/PGF (77%) treated heifers. Conception and pregnancy rates to AI were similar (P>0.10), 57 and 46% for the MGA/Select Synch heifers and 61 and 47% for the MGA/PGF heifers, respectively. Mean estrous response (h) was earlier (P<0.05) for the MGA/Select Synch vs MGA/PGF treatment, 56 vs 61 h post PGF treatment, respectively. In summary, short-term (7 d) MGA feeding preceding the Select Synch protocol produced similar synchronization, conception, and pregnancy rates as the traditional MGA/PGF protocol.