MilkOmicsTM: Functional Development of the Bovine Mammary Gland During the Production Cycle

Objectives: The overall objective is to elucidate the signaling mechanisms underlying the functional development of the mammary gland throughout the entire production cycle, i.e. from dry-off through peak, mid, and late lactation in Holstein cows.  We will use genomic analysis to delineate gene expression profiles in mammary tissue at 9 time points during the lactation cycle.  Our general hypothesis is that functional development of the mammary gland is accompanied by coordinated changes in gene expression.  Thus, expression patterns for genes associated with milk component synthesis such as fat and protein will be up-regulated from parturition through peak lactation.

Specific objectives are 1) To determine temporal coordination of changes in expression for over 13,000 genes during growth, secretory differentiation, activation, and through each lactation stage in mammary tissue, and 2) To relate mammary gene expression profiles with other physiological measurements such as blood prolactin and insulin around parturition, and milk fatty acid profiles during lactation.

Potential benefits:  The proposed research directly addresses a critical limitation in our knowledge of molecular mechanisms associated with control elements that are key during growth and functional development of the bovine mammary gland.  This knowledge should benefit scientists working in a wide range of disciplines pertaining to the dairy cow.  For example, increased knowledge of bovine mammary gland growth and development should be of practical importance to the dairy industry because nearly one third of dairy cows are replaced yearly at a cost that exceeds four billion dollars, yet knowledge of the basic biology of bovine mammary development is far from complete (Capuco et al., 2003).  Ruminant nutritionists could use some of the information generated to design feeding strategies for improving the productive efficiency of cows, which in turn will reduce the environmental impact of milk production.  Information on specific metabolic pathways could be incorporated into existing models of bovine mammary gland metabolism (McNamara and Baldwin, 2000) and improve the accuracy of their predictions.  Geneticists could search for the presence of candidate genes of economic importance within the database and follow their temporal expression.  Most importantly, this study will aid in the functional annotation of the bovine genome and the discovery of novel genes.