Feeding Ferments

How Zoo animals are getting their greens year-round through a new initiative

Fermented foods have gained popularity in recent years for their gut health benefits and shelf life, and some animals at the Zoo have had the opportunity to try their own version of the trend through its new silage initiative. What started as a conversation about how to provide the best food for animals at the Zoo through the colder seasons led to the idea to ferment leafy browse preserving it to ensure a supply of nutritious plant matter through the winter.

“During the spring and summer months and even into early autumn, we’re able to get a lot of leafy browse from Zoo grounds and Cleveland Metroparks reservations,” said Dr. Noah Dunham, Zoo Research Curator. “In the winter, it’s very difficult to come by.”

Rather than source fresh browse from warmer states through the winter, the team had the idea to collect extra leafy material through the summer and ensile it, or pack it into large barrels to ferment, not unlike kimchi. Bringing this idea to life turned out to be a cool example of collaboration between departments at the Zoo – it brought together research scientists, animal keepers, tradespeople, and horticulturists as well as Cleveland Metroparks colleagues in the process.

Zoo horticulturists collect and deliver two truckloads of fresh browse for the animals each day in the warmer months. High in fiber and fed out in large, branched pieces, this element of their diet not only provides nutrition but also encourages natural foraging and chewing behaviors – and increases time spent feeding to closer mimic life in the wild. The goal of providing browse through more of the cold season speaks to the Zoo’s commitment to world-class animal care – and the collaborative effort that achieved it is truly impressive.

Packing unwieldy branches and leaves into a 55-gallon barrel is not the easiest task – in fact, it requires custom equipment. Welder Jason Widdowson designed and fabricated a hydraulic press by modifying a wood splitter and made two different sizes of metal rams to press the plant material into the barrel as tightly as possible. A collar at the top of the barrel lets the team pack browse all the way to the top rim to minimize air in the barrel – a critical detail for anaerobic fermentation. It takes two people one to two hours to fill just one barrel, which holds around 100 pounds of browse.

After three to six months of fermentation, the barrels are opened and the silage is delivered to areas throughout the Zoo. Orangutans, rhinos, kangaroos, and wallabies are among the species to try it so far. With the initial success of the program, the team is looking forward to offering this unique food option again this winter.

“It has been exciting to see how compiling all these different departments’ expertise and ideas has resulted in this silage press and process that really work,” Dunham said, “and a lot of fun to work together and see the results being fed to the animals.”