Why are fish more efficient at converting protein than terrestrial livestock?

Fish have the ability to convert a greater proportion of the protein and energy they receive from feed and turn it into human food (i.e. fillet) than what terrestrial livestock can.

There are two reasons why fish are more efficient at converting feed into human food than terrestrial livestock:

Feed Factor

Fish are able to convert feed into human food more efficiently (i.e. lower food conversion) because they expend less energy on maintaining bodily processes than terrestrial livestock.The feed factor indicates how much the animal has to eat to gain 1 kg. A feed factor of 1.35 means that the salmon needs 1.35 kg feed to gain 1 kg. The pig needs more than twice as much food as the salmon to gain 1 kg, while sheep needs to eat almost six times as much.


Harvest Yield

A higher proportion of a fish can be eaten by humans compared to terrestrial livestock. Harvest yield is yield of gutted animal. Salmon differs from other terrestrial animals  with a yield of 86%. Sheep in comparison has a harvest yield of just 47%.

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