Share this page:

Milk Repository

Did you know the Smithsonian’s National Zoo and Conservation Biology Institute is home to the largest sample collection of exotic animal milk in the world?

The Milk Repository program, based within the Department of Nutrition Science at the Smithsonian’s National Zoo and Conservation Biology Institute, is a world-class scientific resource for veterinarians, nutritionists and animal care specialists. Scientists at the repository preserve and analyze milk samples for their nutritional composition, enabling the replication of formulas based on species-specific nutritional needs. Through the operation of this program, the Smithsonian helps zoos and animal care facilities across North America meet the nutritional needs of neonatal and developing mammals in human care. The Milk Repository program is part of the pan-Smithsonian Cryo-Initiative, which aims to manage and share Smithsonian’s frozen biomaterial to better understand and sustain biodiversity.

The Milk Repository includes more than 16,000 individual samples taken from more than 200 species of mammals—and is still growing!

A Mammal’s First Food

Milk is essential to the growth and development of all young mammals. All milks contain the necessary ingredients for life, but the proportions can differ greatly between species. At the Smithsonian nutrition laboratory, scientists analyze milks to see how much energy, fat, protein, sugar, calcium, phosphorus and other minerals are present, and create nutrition profiles based on that analysis. Formulas developed by Smithsonian scientists have helped young mammals thrive at the Smithsonian and at zoos around the country.

Zoo nutritionist, Erin, poses for the camera holding a screaming hairy armadillo. Erin is wearing a black mask, navy jacket and light blue latex gloves. Sherman's front paws are on Erin's left hand.

Replacing Milks

The Milk Repository is a valuable resource for zoos with young animals who are unable to nurse from their mothers. In the event that a decision to hand-rear or assist feed is made on behalf of a young mammal, the Smithsonian's nutritional composition research may be applied as a resource to help formulate a species-appropriate replacement. In addition to milk composition, nutritionists also develop hand-rearing protocols based on mammal lactation physiology, suckling patterns, volume and feeding frequency.

A Great Cats keeper supplemental feeds the Sumatran tiger cub born July 11, 2017.

The Latest Research

Milk is a complex biological fluid; it contains more than just nutrients. Research conducted at the Smithsonian has enabled not only the discovery of variable milk compositions across species, but have also made preliminary investigations of immunoglobins, maternal gut microbiomes, hormones and growth factors—all of which are important for the health and development of mammals. Milk samples continue to be collected and accepted within the Milk Repository.

Recent Work

A nutrition lab research assistant at the Zoo wearing a full-body snowsuit stands in the freezer where animal milk samples are stored. She holds a bag full of milk samples, and is surrounded by shelves stacked with cardboard boxes full of more samples.

Quiz: Guess That Milk!

Are you a milk maven? Play "Guess That Milk" and try to match these milk samples with the animals they came from.

Take the quiz. 

A nutrition lab research assistant at the Zoo wearing a full-body snowsuit stands in the freezer where animal milk samples are stored. The shelves are stacked with cardboard boxes and she holds a small box filled with tubes of milk samples.
As a research assistant for the nutrition laboratory, Jenna Pastel wears a snowsuit year-round. That’s because she spends a lot of time in a -20 degree Fahrenheit walk-in freezer located in the Zoo’s science building. 
two cheetah cubs with their eyes closed lay in hay
A special delivery of cheetah milk recently arrived at the Smithsonian's National Zoo's milk bank (the largest milk repository in the world). Find out what researchers hope to learn from this unique milk sample.
Keeper Erin Stromberg expresses milk from orangutan mother Batang while she holds her son, Redd.
Smithsonian Conservation Biology Institute scientist Michael Power and primate keeper Erin Stromberg discuss the science behind great ape milk in this Q & A.