Animal control workers and Los Angeles firefighters were called to the scene near Polk Street shortly before 11 a.m., prompting a full closure of the westbound lanes.
Los Angeles Fire Department spokesman Brian Humphrey says three sheep and a dog were rescued and appeared uninjured. Two pregnant cows were hoisted out of the overturned trailer with a crane.
Humphrey says the cows were badly shaken up but didn't appear physically injured. The driver was taken to a hospital in serious condition.
The cause of the crash remains under investigation. All westbound lanes are scheduled to reopen at about 4:30 p.m.
PHOTOS: Animals rescued from overturned trailer on 210 Freeway
CNS contributed to this report.