I'm not a farmer,..you might use it?
Just for your information, found out that it could be dangerous...

from the web...
The drug works by increasing the bodyâÂÂs synthesis of protein thereby causing animals to bulk up and yield more meat. Ractopamine is in the family of drugs known as beta-agonists, which contains many asthma drugs.

from the web
The controversy with exports arises because use of the drug is banned in 160 countries.

I'm not really sure what to say about this drug,...good or bad?

Just my gut feeling say's bad.

from the web...
U.S. farmers have complained that ractopamine induces hyperactivity, muscle damage and even a 10 percent death rate in their pigs and cattle, a concern confirmed by a 2003 study published in the Journal of Animal Science.

Here is a link that might be useful: What is Ractopamine? Dispute Over Drug in Feed Limiting US Meat Exports