Submitted to: Journal of Mammary Gland Biology and Neoplasia
Publication Type: Review Article
Publication Acceptance Date: November 2, 1998
Publication Date: N/A
In order to maximize lifetime milk production, dairy cows are pregnant during approximately 70% of their lactation. Between successive lactations, a nonlactating priod is necessary for optimal milk production in the succeeding lactation. With cessation of milking, alveolar structure is largely maintained and little or no loss of cells occurs. However, increased apoptosis and cell proliferation occur, suggesting that a nonlactating period serves to promote cell turnover prior to the next lactation. Even in the absence of pregnancy, involution in dairy animals occurs at a slower rate than in rodents, alveolar structure is maintained for several weeks and lactation can be reinitiated after four weeks or more of involution. Apoptosis appears to be initiated within a similar time frame to that in rodents, although the maximum proportion of apoptotic epithelial cells is probably lower than In rodents and may be accompanied by an initial increase in cell proliferation. The ability to manipulate apoptosis and cell proliferation during the nonlactating period and during lactation is expected to provide enormous benefits to the dairy industry.