Lactational imprinting: exploiting a novel adaptive response to match milk supply to demand

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The long-term objective of this research is to identify and understand the key factors that regulate milk production by the bovine mammary gland in order to develop new and/or improved methods to enhance the efficiency of milk production. The current proposal is focused on understanding the response of the bovine mammary gland to increased milking frequency (4 times daily vs twice-daily milking) during early lactation. It is well established in mammals that mammary glands typically respond to increased suckling demand of their offspring by acutely increasing milk yield. Importantly, we and others have shown that the bovine udder is uniquely responsive during early lactation such that the increment in milk yield is partially carried over and persists through the remainder of that lactation. Little is known about the mechanisms underlying this response, however the novelty of the biology and the practical implications to the dairy industry are compelling. Over the past several years we have systematically studied this paradigm, mostly using a powerful, half-udder experimental model. We have identified ~ 20 genes as candidate regulators of the response that are coordinately regulated, suggesting a novel, adaptive pathway for modulating mammary function. We propose that the response is an example of "Lactational Imprinting" a novel biological program that regulates milk supply to meet demands of the offspring. The proposed research program is designed to discover: a) the function of specific candidate genes and their interactions in the novel putative adaptive response; b) the biological nature of the unique mammary gland response during early lactation; and c) the potential existence of lactational imprinting of key genes that lead to establishment of a new functional set point for milk yield. These studies will identify the mechanisms involved in the adaptive response to frequent milking and determine the function of individual genes/proteins that make up the putative novel lactational imprinting pathway. Findings are likely to be novel and relevant to other paradigms of adaptive physiology in other organs.