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Estrus synchronization in cattle using estradiol, melengestrol acetate and PGF
J P Kastelic1, D H McCartney, W O Olson
1Research Centre, P. O. Box 3000, Lethbridge, Alberta, Canada T1J 4B1.
Theriogenology
|November 1, 1996
Summary
Estradiol treatments improved estrus detection and pregnancy rates in heifers during cattle estrus synchronization. Including estrogen with MGA and PGF enhanced synchronized pregnancy rates in heifers lacking a functional corpus luteum.
Area of Science:
- Reproductive endocrinology in livestock
- Animal breeding and genetics
- Veterinary reproductive physiology
Background:
- Estrus synchronization is crucial for efficient cattle artificial insemination (AI) programs.
- Melengestrol acetate (MGA) and prostaglandin F2α (PGF) are commonly used for synchronization.
- The role of exogenous estrogen in improving synchronization outcomes requires further investigation.
Purpose of the Study:
- To evaluate the efficacy of estradiol valerate (EV) and estradiol 17beta (E17beta) in estrus synchronization protocols for cattle.
- To determine the impact of estrogen administration on estrus response, AI pregnancy rates, and overall pregnancy rates.
- To assess the effect of estrogen on follicular dynamics and synchronized pregnancy rates in cattle without a functional corpus luteum.
Main Methods:
- Experiment 1: Cattle received MGA and PGF, with half also receiving EV on Day 0. Estrus detection and AI were performed from Days 7-13.
- Experiment 2: Cattle received MGA and PGF, with a third group receiving MGA and E17beta. Synchronization protocols varied based on corpus luteum presence.
- Follicular development was monitored, and pregnancy rates were assessed through AI and bull exposure.
Main Results:
- EV treatment increased estrus detection and AI breeding in heifers at Location 1, but not significantly different pregnancy rates.
- Fall pregnancy rates were higher for EV-treated heifers at Location 2, but not for cows.
- In Experiment 2, the PGF-only group had higher synchronized pregnancy rates in cows than MGA or MGA+E17beta groups. E17beta+MGA improved synchronized pregnancy rates in heifers without a functional CL.
Conclusions:
- Estradiol administration, particularly E17beta in combination with MGA and PGF, can enhance synchronized pregnancy rates in heifers, especially those without a functional corpus luteum.
- Estrogen treatment appears to induce follicular regression and the emergence of a new follicular wave, potentially improving synchronization.
- Estradiol's inclusion in estrus synchronization programs shows promise for improving reproductive efficiency in cattle, particularly in heifers.
