Ad lib fed的用法和样例：
- We were told to help ourselves to the food ad lib.
- Effect of Dietary Tryptophan Levels on Serum IGF-1 in Limited and Ad lib Fed Weaned Piglets
- The actress often forgot her line but was very good at ad lib.
- I had forgotten to bring my notes and had to speak ad lib.
- The ad lib joke in the play is the best.