Fig 1. Frequency of ear biting in pigs kept under different sanitary conditions and fed a diet with either a low or normal dietary protein level and a basal or supplemented amino acid profile.

Ear biting was recorded during live ad libitum sampling for 100 min per pen in total. The bars represent the raw means per treatment group ± standard error of the mean. LSC = low sanitary conditions, HSC = high sanitary conditions, LP = low dietary crude protein level (white bars). NP = normal dietary crude protein level (grey bars), AA-B = basal dietary amino acid profile (striped bars), AA-S = supplemented dietary amino acid profile containing 20% more Met, Thr, and Trp compared with the basal profile (dotted bars), SC = sanitary conditions, AA = amino acid profile.