Abstract

Understanding the mammary responses that occur at the cessation of milking whether natural, forced, or which occur at the end of the milking season and during the subsequent initiation of mammary involution (Holst et al., 1987; Hurley, 1989) has relevance in milk production traits such as milk yield, persistency and extended milking intervals and may suggest ways of improving milk production in later lactation (Stelwagen, 2001) (Vetharaniam et al., 2003). The proportions of secretory, support and milk storage components vary significantly between the alveolar (main milk synthesis), peripheral (a several cm thick layer of secretory tissue surrounding the main alveolar bed) and cisternal (main milk storage area adjoining the teats) compartments of the udder (Farr et al., 1996; Sordillo and Nickerson, 1988; Weber, 1977). In addition, variations in the local proportions of these components has also been observed in the main alveolar areas and dramatic variations of gene expression depending on the local mammary tissue composition have been observed (Molenaar et al., 1992). Ignorance of the effect on gene expression profiles resulting from sampling variations could lead to improper interpretation of experimental results and hence there is a need for more extensive spatial and temporal surveys to be done.

AJ, Molenaar, VC Farr, KE Oden, TT Wheeler, CD McMahon, LL Good, K Stelwagen, K Singh, and SR Davis

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 5-7, 2004