Different protocols using PGF₂α as ovulation inducer in Nelore cows subjected to estradiol-progesterone timed AI...

Area of Science:

• Reproductive biology and endocrinology in cattle.
• Animal science and veterinary medicine.
• Livestock reproduction management.

Background:

• Timed artificial insemination (TAI) protocols are crucial for efficient cattle breeding.
• Hormonal interventions, including prostaglandin F2α (PGF) and estradiol cypionate (ECP), are used to synchronize ovulation.
• Optimizing TAI protocols aims to improve pregnancy rates and reduce management complexity.

Purpose of the Study:

• To evaluate the efficacy of a prostaglandin F2α (PGF) analogue in inducing ovulation and enhancing pregnancy rates in cattle undergoing TAI.
• To compare the reproductive outcomes of PGF-based ovulation induction protocols with those using estradiol cypionate (ECP).
• To assess the feasibility of alternative PGF administration routes (intramuscular and subcutaneous) for TAI synchronization.

Main Methods:

• Three experiments involving cattle treated with intravaginal progesterone-releasing devices (CIDR), estradiol benzoate (EB), and various hormonal regimens.
• Experiment 1 & 2: Compared ECP with ECP plus PGF for ovulation and pregnancy rates after TAI.
• Experiment 3: Evaluated ECP versus subcutaneous (SC) or intramuscular (IM) PGF administration without ECP, assessing estrus display and pregnancy per AI (P/AI).

Main Results:

• No significant differences in ovulation interval or proportion of cows ovulating were observed between ECP and ECP-PG groups in Experiment 1.
• Experiment 2 showed similar pregnancy rates (approximately 55%) between cows treated with ECP and those with ECP plus PGF.
• Experiment 3 indicated that while PGF (SC or IM) did not differ in P/AI from ECP, the ECP group exhibited higher estrus expression, which correlated with improved P/AI.

Conclusions:

• Intramuscular or subcutaneous PGF administration can effectively induce ovulation for TAI in cattle, yielding pregnancy rates comparable to ECP.
• Subcutaneous PGF on the day of CIDR removal presents a potentially simpler management strategy for achieving similar reproductive outcomes.
• Estrus expression prior to TAI is a significant factor influencing pregnancy success in PGF-based protocols.