Estrus synchronization in beef cows: comparison between GnRH+PGF2alpha+GnRH and PRID+PGF2alpha+eCG

Area of Science:

• Reproductive biology
• Animal science
• Veterinary medicine

Background:

• Estrus synchronization is crucial for efficient artificial insemination in beef cattle production.
• Optimizing synchronization protocols can improve reproductive efficiency and economic returns in beef herds.
• Understanding the impact of different hormonal treatments on ovulation and pregnancy rates is essential.

Purpose of the Study:

• To compare the efficacy of two estrus synchronization protocols in suckled beef cows.
• To evaluate the effects of PRID+PGF2alpha versus GnRH+PGF2alpha+GnRH on ovulation and pregnancy rates.
• To assess the influence of factors like cyclicity and year on treatment outcomes.

Main Methods:

• A 2-year study involving 340 Charolais and Limousin beef cows across 26 herds.
• Two groups were compared: Group 1 (PRID+estradiol benzoate+dinoprost+eCG) and Group 2 (GnRH+dinoprost+GnRH).
• Hormonal concentrations, ovulation, early pregnancy, and pregnancy rates (ultrasonography) were monitored.

Main Results:

• No significant difference in overall pregnancy rates between Group 1 (53.8%) and Group 2 (46.3%) at 35-45 days.
• Ovulation rate was significantly higher in Group 1 (90.8%) compared to Group 2 (77.1%).
• The GnRH protocol's ovulation rate was significantly affected by pre-treatment cyclicity, especially in anestrous cows.

Conclusions:

• While overall pregnancy rates were similar, the PRID+PGF2alpha protocol demonstrated a superior ovulation rate.
• The GnRH+PGF2alpha+GnRH protocol showed reduced efficacy in inducing ovulation in anestrous beef cows.
• Protocol selection should consider the cyclicity status of the cow population for optimal results.