Farmed Seafood and Livestock Stack Up Differently Using Alternate Feed Efficiency Measure

A new study by researchers at the Johns Hopkins Bloomberg School of Public Health’s Center for a Livable Future found that, contrary to widely held assumptions, farmed fish and shrimp convert protein and calories in feed to edible seafood at rates similar to livestock (i.e., cattle, pigs, and chickens). The study contributes new insights into what is known as feed conversion efficiency – that is, the efficiency of the process by which feed is turned into meat – across species, and uses a new analysis to assess this efficiency. Researchers found that average protein and calorie retention across nine types of farmed fish and shrimp are lower than chickens and similar to pig and cattle production. They estimate that 19 percent of protein and 10 percent of calories in feed for aquatic species are ultimately made available in the human food supply. The similarity to livestock when using these efficiency measures is the opposite of the expected result based on weight-based feed conversion ratios. Comparing all terrestrial and aquatic animals in the study, chickens are most efficient for protein retention, followed by Atlantic salmon, rainbow trout, whiteleg shrimp and pigs.