The literature strongly points towards the fact
that antibiotics can have amino acid saving properties. So it seems that
animals fed without antibiotics need more amino acids in the diet for optimal
growth and performance. Trials at Schothorst feed research investigated
whether the AGP ban really has an effect on the amino acid requirements.
This article can also be found at Feed Mix, volume 14, no. 1
22_FM14_01 AGP ban effects.pdf