Table 1.

Different measures/traits of feed efficiency

Measure/trait	Abbreviation	Formulaa
Feed conversion ratio (gross efficiency)	FCR	FCR=FI/PO
Residual feed intake	RFI	RFI=FI – (α + β1 BW0.75 + β2 ΔBW)
Coefficient of digestibility	CDU	CDU = 100–100(DEW/FI)
Maintenance efficiencyb	ME	ME=BW/FIn

^aFI – feed intake, PO – production outputs, BW – body weight, BW^0.75 – metabolic body weight, FI_n – feed intake at zero change of body weight, DEW – weighted dried excreta, α, β₁, β₂ – regression coefficients, ΔBW – change of body weight

^bMaintenance efficiency is defined as the feed needed to maintain the energy requirements of the animal, i.e., to keep temperature level, body movement, and basal metabolism level, without affecting the body weight