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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #153673
Title: IMPROVEMENT IN ESTROUS SYNCHRONIZATION AMONG BEEF HEIFERS

Author
item Geary, Thomas
item FUNSTON, R - MSU EXTENSION SERV

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Popular Publication
Publication Acceptance Date: 10/1/2002
Publication Date: 1/15/2003
Citation: GEARY, T.W., FUNSTON, R.N. IMPROVEMENT IN ESTROUS SYNCHRONIZATION AMONG BEEF HEIFERS. RESEARCH UPDATE FOR FORT KEOGH LIVESTOCK AND RANGE RESEARCH LABORATORY. p. 39-40. 2003.

Interpretive Summary: The melengestrol acetate/prostaglandin (MGA/PGF) protocol has long been considered the industry standard for synchronizing estrus in beef heifers. The traditional MGA/PGF protocol includes feeding MGA to each heifer at a rate of 0.5 mg per day for 14 days followed by administration of PGF 17 days after the final day of feeding MGA. While it has served as an industry standard for beef heifers, it is not widely used for beef cows because of its length (31 days) and increased incidence in twinning. This article summarizes several studies over the last 3 years that tried to improve upon the MGA/PGF protocol in beef heifers. In study 1, beef heifers were synchorized with the MGA/PFG protocol and either bred ~ 12 hr after estrus (EAI) or times AI (TAI) 72 hr after PGF. Conception rates, but not pregnancy rates to AI, were higher among EAI heifers. In study 2, heifers received either the MGA/PGF protocol or were fed MGA for 7 d before receiving the Select Synch protocol. Synchronization, conception, and pregnancy rates were similar between treatments. In study 3, heifers received either the MGA/PGF protocol, the Select Synch Protocol, or the Select Synch protocol preceded by the 7 d of MGA feeding. Synchronization rates were higher for heifers receiving the MGA/PGF protocol, but conception rates were similar across treatments. These studies revealed alternatives available to producers wishing to synchronize estrus in heifers and the problems associated with each protocol.

Technical Abstract: The melengestrol acetate/prostaglandin (MGA/PGF) protocol has long been considered the industry standard for synchronizing estrus in beef heifers. The traditional MGA/PGF protocol includes feeding MGA to each heifer at a rate of 0.5 mg per day for 14 days followed by administration of PGF 17 days after the final day of feeding MGA. While it has served as an industry standard for beef heifers, it is not widely used for beef cows because of its length (31 days) and increased incidence in twinning. This article summarizes several studies over the last 3 years that tried to improve upon the MGA/PGF protocol in beef heifers. In study 1, beef heifers were synchorized with the MGA/PFG protocol and either bred ~ 12 hr after estrus (EAI) or times AI (TAI) 72 hr after PGF. Conception rates, but not pregnancy rates to AI, were higher among EAI heifers. In study 2, heifers received either the MGA/PGF protocol or were fed MGA for 7 d before receiving the Select Synch protocol. Synchronization, conception, and pregnancy rates were similar between treatments. In study 3, heifers received either the MGA/PGF protocol, the Select Synch Protocol, or the Select Synch protocol preceded by the 7 d of MGA feeding. Synchronization rates were higher for heifers receiving the MGA/PGF protocol, but conception rates were similar across treatments. These studies revealed alternatives available to producers wishing to synchronize estrus in heifers and the problems associated with each protocol.