Protein efficiency ratios

A classic feeding-trial measure of protein quality, abbreviated PER: growing animals receive the test protein, and weight gained per unit of protein eaten becomes the score. Widely applied in comparing food proteins, it assumes dietary protein goes entirely toward growth, an approximation that works for young animals but oversimplifies human nutrition. Higher values mark proteins that support growth efficiently, with animal proteins generally outscoring most plant proteins. Though largely superseded by digestibility-corrected scoring systems, it remains a familiar reference in older literature and product specifications.