Surely there is nothing wrong with the concept of FCE.  The problem arises from the fact that energy input (feed) and energy output (meat) per kg are not the same.  The energy in feed is the same for all animals, but the energy concentration in the meat varies between individuals according to maturity / frame type.  FCE is a prime example of man measuring inappropriate criteria accurately.  FCE is biased toward lean, late maturing genotypes.  Lean bulls will produce lean cows that will have to be fed in order to be “productive”.
There is a common denominator between FCE and GCE which is positive – Relative Intake.  There is also a common denominator that is negative – Inherent Body Condition.

What is the most appropriate measurement of  feed / grass conversion efficiency ?The faster an individual animal grows in relation to size the greater the efficiency.  In order to be equally efficient, animals of different sizes have to grow in proportion to their size.  Fullness of the package or 12 month maturity are the easiest, most comprehensive and best measures of efficiency.

The problem is that animals can not eat in proportion to their size. Therefore small frame animals have an unfair advantage and large frame animals are genetically handicapped.  All selection criteria should be positively correlated to Relative Intake.

A veld adapted genotype can also perform well on a feedlot ration, particularly if management manipulate frame size / body condition (backgrounding) prior to the feedlot phase.

Cattle bred to perform in a feedlot will lose veld productivity.
Cattle bred for veld productivity can be efficiently fattened on a feedlot ration.