A 100-Year Review: Mammary development and lactation

Area of Science:

• Dairy Science
• Animal Physiology
• Reproductive Biology

Background:

• Early dairy science research focused on identifying key hormones (e.g., steroids, prolactin, growth hormone) regulating mammary development and lactation.
• Advancements in sensitive assays enabled measurement of hormones and growth factors, leading to hypotheses on mammary cell proliferation and function.
• Fundamental knowledge of milk removal, milking frequency, and management for successful lactation has been established.

Purpose of the Study:

• To evaluate the applicability of historical mammary development and lactation principles to modern, high-producing dairy animals.
• To investigate mechanisms underlying the positive effects of early increased milking frequency on subsequent milk yield.
• To explore strategies for improving lactation persistency and the potential for early management to "program" future mammary productivity.

Main Methods:

• Review of historical and current research on mammary gland physiology and lactation in dairy animals.
• Analysis of the impact of evolving technologies, including molecular techniques and "-omics" approaches, on understanding mammary function.
• Consideration of data integration challenges faced by dairy farmers in managing operations.

Main Results:

• While significant progress has been made in understanding mammary development and lactation, fundamental questions persist regarding high-producing cows.
• The long-term effects of early management practices, such as milking frequency, on lactation persistency and productivity require further elucidation.
• The integration of vast amounts of molecular data (gene expression, cell signaling) remains a challenge for comprehensive understanding.

Conclusions:

• Revisiting foundational dairy science principles is essential for addressing contemporary challenges in dairy animal production.
• Further research is needed to bridge the gap between molecular-level understanding and practical application in dairy farm management.
• Identifying a unifying framework ('Rosetta stone') is crucial for interpreting complex data and optimizing dairy cow health and productivity.