Introduction
Dr. Paul Fricke is a professor of Dairy Science and Extension dairy cattle reproduction specialist at the University of Wisconsin-Madison. His research focuses on developing and improving methods for reproductive management of dairy cattle and understanding the biology underlying the many reproductive problems presented by modern dairy cattle. The goal of his Extension program is to improve reproductive efficiency of dairy cattle by applying knowledge gained through scientific research to develop practical management strategies, assess new reproductive technologies, and disseminate that information throughout Wisconsin, nationally, and globally.
Whitney Brown is a PhD student with Dr. Paul Fricke in the Department of Animal and Dairy Sciences at UW- Madison. The focus of Whitney’s dissertation is methods to improve reproductive management of replacement dairy heifers. Whitney will overview the results from a recent field trial with the aim of improving synchrony to a protocol for timed AI in dairy heifers.
Chapters
02:10 Overview
02:17 Background of why this is important
07:15 Modifications to a 5-day CIDR-Synch protocol
19:51 Hypotheses
21:38 Experimental Design
22:25 Results
28:26 Summary
Highlights
📊 Larger-scale fertility trials are planned to confirm findings and optimize dairy heifer reproductive protocols.
🐄 The dairy industry has experienced a “reproduction revolution” since 2000, improving conception rates and reducing days open in cows.
🥚 The 5-day CIDR synchronization protocol is the gold standard for dairy heifer fertility but has limitations, including early estrus and low ovulatory response rates.
🔄 Delaying insemination after GnRH injection in the 6-day CIDR protocol can improve fertility outcomes with sexed semen.
Key Insights
📉 Reproduction Revolution and Improved Fertility Trends: The long-term increase in days open (time between calving and conception) from 1955 to 2000 reflected declining reproductive performance in dairy cows. However, since 2000, advancements such as timed AI protocols and automated activity monitoring have reversed this trend, significantly improving conception rates and shortening days open, which is crucial for dairy farm profitability and herd health. This highlights the importance of integrating new reproductive technologies for herd improvement.
🐄 5-Day CIDR Protocol as a Standard but Imperfect Tool: The 5-day CIDR protocol is widely adopted because it achieves conception rates around 60% in heifers, comparable to conventional inseminations. However, approximately 30% of heifers exhibit early estrus, requiring multiple inseminations and complicating synchronization efforts. This reveals the inherent biological challenges in synchronizing heifers compared to lactating cows, stemming from their unique hormonal profiles and follicular dynamics. Extending progesterone exposure to six days nearly eliminates early estrus but shifts the timing of ovulation later. When insemination timing remains unchanged (timed AI at 72 hours), this leads to insemination occurring too early relative to ovulation, particularly detrimental when using sexed semen, which has a narrower fertile window. This insight underscores the critical need to align insemination timing precisely with physiological changes induced by protocol modifications.
🔄 Delayed Insemination Post-GnRH Injection Improves Fertility with Sexed Semen: A follow-up study demonstrated that delaying insemination by 8 hours after the GnRH injection in the 6-day CIDR protocol recovers fertility rates by better matching insemination to ovulation timing. This finding is significant for practical dairy operations using sexed semen, as it offers a concrete way to improve pregnancy outcomes while maintaining the benefits of early estrus suppression.
📈 Need for Larger-Scale Trials to Validate Protocol Improvements: Whitney’s current study offers promising physiological data but has limited sample size for definitive fertility conclusions. The planned large-scale field trials with hundreds of heifers will provide more robust data on pregnancy rates and losses, which is critical for translating these synchronization protocol modifications into widespread practical recommendations on commercial farms. This illustrates the ongoing iterative nature of applied animal science research.
Summary
The webinar provided an insightful update on dairy heifer reproductive management, blending foundational physiological understanding with applied research aimed at refining synchronization protocols. It demonstrated how subtle changes in hormone administration timing and pre-treatment can profoundly affect ovulatory responses and fertility outcomes. With dairy producers increasingly adopting advanced reproductive technologies alongside strategic genetic decisions like beef semen use, research efforts such as Whitney Brown’s are vital to optimizing herd productivity and farm profitability. The session also emphasized the importance of continued research, collaboration, and extension outreach to translate scientific advances into practical tools for the dairy industry.
