Control and induction of ovulation in cattle

Area of Science:

• Veterinary Science
• Reproductive Biology
• Animal Science

Background:

• Controlling and inducing ovulation in cattle is crucial for efficient breeding programs.
• Progesterone administration is a common method for synchronizing estrus and ovulation.

Purpose of the Study:

• To evaluate the efficacy of progesterone-impregnated coils for ovulation control in heifers and beef cows.
• To determine optimal progesterone treatment durations and the necessity of luteolytic agents for ovulation induction.

Main Methods:

• Cattle were treated with progesterone-impregnated coils for varying durations (7, 9, 12, or 14 days).
• Luteolytic agents (prostaglandin or estradiol benzoate) were used in conjunction with shorter progesterone treatments.
• Hormonal profiles, including progesterone and luteinizing hormone (LH), were monitored.
• Fertility rates were assessed after different treatment protocols.

Main Results:

• A 14-day progesterone treatment was necessary for precise estrus onset.
• Shorter treatments (7-12 days) required a luteolytic agent for ovulation induction.
• Fertility was normal with 7-12 day treatments, but requires further evaluation for 14-day treatments.
• Progesterone coils failed to maintain adequate luteal-phase progesterone levels, and increasing coil concentration did not improve blood progesterone.
• A pre-coil removal rise in LH occurred when progesterone dropped below 1.5 ng/ml, indicating potential ovulation readiness.

Conclusions:

• Progesterone coils alone are not fully effective for maintaining luteal-phase progesterone or inducing consistent ovulation in cattle.
• The precise duration of progesterone treatment and the use of luteolytic agents are critical for successful ovulation induction.
• Inadequate LH release patterns may explain anovulation in postpartum cattle, suggesting potential issues with episodic LH secretion.