These youths are full of animal spirits.

（误译）这些年轻人充满动物精神。
（正译）这些年轻人充满活力。

animal spirits 精力充沛
类似表达如下：

1. full of energy

You are strong and full of energy.
你身强体壮，充满活力。

That old man remained full of energy.
那位老人还是那么精力充沛。

After rests, we are full of energy to go down quickly.
经过短暂的休息讨论后，大家的精力都很旺盛，下山速度明显加快。

2. as fresh as paint 精神饱满的

The children looked as fresh as new paint after their bath.
孩子们洗完澡后显得精神焕发。

Though nearly seventy years of age, he is still hale and fresh as paint.
他虽年近七十，但身子硬朗，精力充沛。

After living a while in the open, campers become as fresh as paint. They feel rejuvenated.
经过一段时间的野外生活，露营者变得精神饱满，感到恢复了青春的活力。

3. be full of guts
[美国俚语]胆量极大；精力充沛；（小说、图画等）很有精神；[美国俚语]厚颜无耻