When a cow eats hay how much of

the hay's original energy is

recovered by the cow?

10%

Explanation:

We use the energy pyramid to figure this out:

.01% - A pex Predators

0.1% - Tertiary Consumers

1% - Secondary Consumers

10% - Primary Consumers

100% - Primary Producers

Cows are primary consumers, as they eat grass and hay (which are primary producers). So however much they eat of grass and hay, you multiply by 10% to get the total amount of energy that the cow gets.