Giraffes like to eat leaves. This is evident on the African savannah where the animals stretch their long necks to reach the leaves of the acacia trees. The giraffe's digestive system is specifically designed to digest large quantities of browse – but what does a giraffe do in a zoo in Denmark, where there are no acacia trees or even leaves on the domestic trees for half of the year?

Scientists from Aarhus University are busy devising a solution to this. They are testing if giraffes are willing to eat silage made from leaves and, if so, whether there may be a practical and effective way to harvest and ensile browse. The scientists have also tested whether the giraffes show preferences for specific ensiled crops.

- Since giraffes in the wild primarily eat leaves, the recommendation is to feed the giraffes in captivity as much browse as possible. However, in practice it’s very difficult if not impossible to get the quantities of fresh leafy material that you need for a group of giraffes, especially during wintertime. Giraffes are therefore typically fed alfalfa hay and different kinds of feed pellets, often supplemented with some fruit and vegetables, explains PhD student Cathrine Sauer from the Department of Animal Science at Aarhus University.

The challenges are to devise a fast and effective method of harvesting fresh leafy material and to subsequently preserve the harvested material for wintertime feeding in particular.

Giraffe preferences tested

Making silage from various crops is a routine procedure in agriculture, so maybe some of the lessons learned there could be transferred to giraffe feed? Silage is not widely used in zoos since leaf silage production is somewhat problematic. Experience has shown that the harvest is very labour-intensive since the leaves are often harvested by hand.

- I visited a zoo in Switzerland where they told me that it takes them about two weeks and ten men to pick and harvest one and a half tonnes of leaves. For my feeding trial I would need 10 tonnes of leaf material and a zoo would need to use much more in the course of a year, so picking by hand is a fairly impractical method, says Cathrine Sauer.

First, the scientists had to find out whether the giraffes were at all interested in eating silage. The giraffes at Copenhagen Zoo were therefore presented with a buffet of one kilogram portions of different silages. How much they ate of the various silages was then measured to give an expression of their preference. The options included silage made from alfalfa, chopped willow, caraway, chicory, red clover and birdsfoot trefoil.

- It was obvious that giraffes have different tastes, but generally they appeared to like eating silage, also the one we made from willow, says Cathrine Sauer.

Fast food requires a fast production

The next step was to find a quick and effective method of harvesting and ensiling the willow. Young re-growths of willow were mechanically harvested and chopped by Ny Vrå Bioenergi I/S before being baled in large round bales by Mosegaarden I/S. The bales are now left to ensile for  at least eight weeks before the silage is ready to be served.

The whole harvesting process was so productive that four people could make nine tonnes of willow silage in just one morning.

- It is totally unprecedented that so much browse silage can be produced so fast. This means that it may be practically possible to feed giraffes in zoos willow silage harvested in Denmark, explains Cathrine Sauer. In Copenhagen Zoo, she will be looking at whether giraffes will eat larger quantities of willow silage than the appetizer they were offered in the initial investigations and whether this will affect their appetite and behaviour.

For further information please contact: PhD fellow Cathrine Sauer, Department of Animal Science, cathrine.sauer@anis.au.dk, telephone: +45 6171 6000