We had to we had the calf in the back seat and the chickens in the front
Yes, just stuff animals in the trunk. An unsecured animal would never become disoriented flailing around in there and injure themselves in such an environment [/obvious sarcasm].
You didn't have to, you chose to. Was there something wrong with taking two trips? Is there something wrong with responsible transporting? If someone came to pick up goats from place and were planning on shoving them in the trunk of their car, I'd hand them their money back and say gtfo. Too many things that can go wrong, not worth the risk.