Adding amino acids like threonine and lysine completely compensates the lack of growth promoters in pig feed. Studies by the Dutch institute Schothorst Feed Research support this conclusion.
The institute discovered that pigs predominantly need more threonines when
not being fed growth promoters. When the animals are still being fed growth
promoters, however, adding lysine or threonine does not appear to
work.
Pigs having a threonine-lysine percentage of about 65 to 70% in the
feed perform as well as when being fed meals containing growth
promoters.
Related website:
Schothorst Feed Research
Related
article:
AGP effects on amino acids
requirements