Effect of Prepartum Milk Removal on Quantitative Morphology of Bovine Lactogenesis

The effect of prepartum milking on bovine mammary histology and milk composition was studied in five Holstein cows. One udder half was milked twice daily starting 10 days before the estimated calving date. One udder half was not milked until 2 days postpartum when all quarters were milked and two tissue samples per quarter were taken for morphological analyses. Lactose, casein, and fat concentrations differed from prepartum-milked to postpartum-milked quarters (.82, −1.44, and 3.29%). Quarters milked prepartum were more developed: mature epithelium 24.8%, immature epithelium −8.9%, total epithelium 15.6%, stroma −24.8%, and alveolar lumen 8.5%. Most alveolar cells in prepartum-milked halves had prominent rounded basal nuclei, hypertrophied secretory vesicles, and a mixed array of lipid droplets. Cells within alveoli were morphologically similar. Secretory epithelial cells from postpartum-milked glands had irregular randomly located nuclei, indistinct Golgi, variable lipid content, and less cytoplasm. These differences demonstrate the importance of prepartum-product removal on secretory cell development and subsequent milk production.