Gene expression in bovine mammary gland in response to increased milking frequency as determined by microarray and SAGE

Transcript profiling was performed by Affymetrix microarray analysis and SAGE to characterize changes in gene expression in the bovine mammary gland in response to 4× versus 2× daily milking during the first week of lactation. These changes in gene expression may contribute to the increased milk production observed in response to increased milking frequency. Our results indicate that increased milking frequency alters expression of genes in the mammary gland related to increased extracellular matrix remodeling, neovascularization, metabolism, cell proliferation and apoptosis. Keywords: Physiological response to stimulus Overall design: Multiparous Holstein cows were milked either 2× daily (Control, n = 3) or 2× daily from day 1 to 3 of lactation, and 4× daily beginning at day 4 of lactation until day 21 post partum (IMF4, n = 4). The milking intervals were approximately 12 hours for Control cows and 9, 3, 9, and 3 hours, respectively, for IMF4 cows. Mammary biopsies were obtained at approximately day 7 of lactation for extraction of total RNA and subsequent transcript profiling my microarray (Affymetrix). Pooled Control and IMF4 RNA samples were used to synthesize two SAGE libraries using the Long SAGE kit by Invitrogen.