Repeated oestrus synchrony and fixed-time artificial insemination in beef cows

Area of Science:

• Veterinary Science
• Animal Reproduction
• Beef Cattle Production

Background:

• Natural service in beef herds can lead to challenges in genetic selection and disease transmission.
• Synchronized estrus and artificial insemination (AI) offer potential for controlled breeding and genetic improvement.
• Investigating non-natural service breeding methods is crucial for enhancing reproductive efficiency in beef cattle.

Purpose of the Study:

• To evaluate the feasibility of breeding spring-calving, single-suckled beef cows without natural service.
• To assess the efficacy of repeated estrus synchronization and fixed-time AI protocols over two breeding seasons.
• To determine pregnancy rates and identify factors influencing reproductive success in a non-natural service system.

Main Methods:

• Cows were synchronized using norgestomet implants and prostaglandin injections for timed AI.
• Repeated synchronization and AI protocols were employed for first, second, and third services.
• Pregnancy was diagnosed using milk progesterone assays and confirmed by rectal palpation.

Main Results:

• First-year pregnancy rates were 56% (1st service), 69% (2nd service), and 40% (3rd service), with 17% barren cows.
• Second-year pregnancy rates were 58% (1st service), 48% (2nd service), and 33% (3rd service), with 20% barren cows.
• Milk progesterone assay accuracy for pregnancy diagnosis was high, at 84% and 87% over the two years.

Conclusions:

• Fixed-time AI following estrus synchronization is a feasible alternative to natural service in beef cows.
• Reproductive performance varied across successive services, indicating potential for optimization.
• Accurate pregnancy diagnosis via milk progesterone assays supports efficient management of AI programs.