A comparison of progestin-based protocols to synchronize estrus in postpartum beef cows

Area of Science:

• Reproductive physiology in beef cattle
• Estrus synchronization protocols
• Artificial insemination efficiency

Background:

• Effective estrus synchronization is vital for efficient beef cattle reproduction.
• Progestin-based protocols, including melengestrol acetate (MGA), are commonly used.
• Optimizing synchronization protocols impacts herd reproductive performance.

Purpose of the Study:

• To compare two progestin-based estrus synchronization protocols (MGA Select and 7-11 Synch) in postpartum beef cows.
• To evaluate estrous response, interval to estrus, estrus synchrony, and pregnancy rates.
• To determine the efficacy of each protocol for improving reproductive outcomes.

Main Methods:

• Two groups of postpartum beef cows (n=109 MGA Select, n=111 7-11 Synch) were assigned to different progestin-based synchronization protocols.
• Protocols involved melengestrol acetate (MGA), GnRH, and prostaglandin (PG) administration at specific intervals.
• Estrus was monitored using HeatWatch, and artificial insemination (AI) was performed 12 hours after estrus onset.

Main Results:

• Estrous response (92% MGA Select, 91% 7-11 Synch) and final pregnancy rates (86% MGA Select, 90% 7-11 Synch) did not differ significantly between protocols.
• The 7-11 Synch protocol resulted in a shorter mean interval to estrus (52 h vs. 65 h) and improved estrus synchrony compared to MGA Select.
• Serum progesterone concentrations at PG administration differed significantly between treatments (P < 0.01).

Conclusions:

• Both MGA Select and 7-11 Synch protocols are effective for estrus synchronization and achieving pregnancy in postpartum beef cows.
• The 7-11 Synch protocol offers improved synchrony of estrus, potentially enhancing AI efficiency.
• Estrus response and fertility rates were comparable across both evaluated synchronization strategies.