Inside the milk bank creating infant formula for orphaned animals

Orca milk smells dizzyingly fishy. Seal milk has a rich orange hue. Reindeer milk, perhaps fittingly, is as thick as eggnog. Not that I am tempted to try it, or any of the other unusual milks I can see stacked on shelves from floor to ceiling. I have donned a puffy winter jacket and stepped inside the freezer that houses the largest collection of animal milk in the world, containing that of everything from tree shrews to two-toed sloths and giant anteaters.

The collection, housed at Smithsonian’s National Zoo in Washington DC, is more than a cabinet of curiosities – it is a critical resource for staff at this zoo and others around the world tasked with feeding orphaned infants. By studying all this white – and not-so-white – stuff, Smithsonian scientists can create custom infant formulas that will give the animals in their care the best possible start in life.

As their understanding of milk has improved, however, they have realised that their formulas are missing an important component: microbes. Now, as they explore the microbial diversity contained in different milks and the benefits these organisms bring, they are striving to replicate this in lab-made milk – not only to better assist young animals in the zoo, but also to aid the survival of some of the rarest species in the wild.

“The objective isn’t necessarily to freeze milk, archive it…