A method to collect to high volumes of milk from mice (Mus musculus)

Collecting milk samples from mice (Mus musculus) may be interesting for a variety of preclinical research. References in the literature for protocols describing how to milk a dam are scarce, and a major limitation of such protocols is the small sample volume that is generally collected. The aim of our study was to develop a practical protocol to collect substantial amounts of milk from mice. Adult female outbred NMRI and inbred BALB/c mice with nursing litters were used in this study. The milking was carried out on days 7–12 after parturition. The pups were separated from their mothers for 6–12 h before milking to allow accumulation of milk in the glands. Dams were anesthetized using either an injectable mixture of midazolam and ketamine, or by use of the inhalational agent isoflurane. To induce milk flow, the mice were given 2-8 IU of oxytocin intraperitoneally. The milk was collected using an electric human breast pump that was modified to accommodate mouse nipples and to handle small liquid volumes. With this protocol, the total amount of milk collected from each dam per each milking ranged between 0.2 and 1.5 mL. We concluded that this milking method provides an excellent means for acquiring substantial amounts of mouse milk.