“performance index” of growing chickens

In commercial broiler production and in research on growth of chickens, it is common practice to compare groups with respect to weight and with respect to feed efficiency which is defined as the gain per unit of feed consumed. It often happens that groups are arranged in one sequence when compared on the basis of mean live weight and in an entirely different sequence when compared on the basis of efficiency. It then becomes desirable to make an over-all comparison that takes account of both weight and efficiency. Very frequently this is accomplished by multiplying mean live weight by efficiency or dividing mean live weight by feed conversion which is the reciprocal of efficiency. The resulting figure, designated the “performance index,” “efficiency index,” or “performance efficiency” has been used both by commercial broiler producers and by research workers (Lanson and Smyth, 1955; Wilder et al., 1955). Wilder et al., after …