Energy flow on a farm

Title Info
Common name Cow
Scientific name Bos taurus
Taxonomic group Bovidae
Source Dan L. Perlman
Ecological interactions Mutualism
Human impacts Agriculture
Organisms Animals; Bacteria
Lessons Energy Flow
Date October 09, 2005
Location Wisconsin,USA,North America
Energy flow on a farm: sun, grass, cows
Related materials: Grass and energy flow
This image can be used to show a few of the many energy transformations that occur within an ecosystem, including the capture of solar energy, fermentation by bacteria (in two locations), and digestion by the cow.

Energy flow on a farm, Wisconsin. This image shows the many transformations that energy undergoes on its way through an ecosystem. Solar energy is captured by the leaves of trees, shrubs, and grass--some of which is eaten by the cow seen in this picture. The cow's digestive system contains many billion bacteria and protozoa that ferment and break down the difficult-to-digest grass into chemical compounds that the cow can herself absorb and use as nutrition. This is an example of mutualism; the cows would not be able to digest the grass without the bacteria and protozoa, which get a warm, sheltered location in which to live.

Much of the solar energy captured on the farm is stored in grass that is not eaten directly; instead it is stored in the hay rolls seen on the right. Since cows cannot digest the grass, bacteria that naturally occur on the hay are employed to ferment the hay to more useful compounds. However, if oxygen-requiring bacteria are allowed to multiply on the hay, they will not create the most useful chemical product (lactic acid). So, the hay must be stored in a fairly air-tight container (the silo, on the left) so that anaerobic bacteria, which do not need oxygen, can play the primary role in breaking down the hay. Over a period of 2-3 weeks the lactic acid that these bacteria create leads to an acidic environment that eventually stops the further bacterial action and preserves the silage in an edible, long-lasting form--which can be fed to cows during the winter.