Many people don't realize how large the animal drug market is. Pfizer's used to have around 16,000 people and around $3 billion in animal drugs. I'm not sure what they have today.
The people at Tyson aren't taking the drugs from Novartis; the animals are. However, people with headaches probably down a lot of Excedrin, also owned by Novartis.
NVS biggest drug end user: Tyson? The largest livestock based food producer in the US?