方法：选用同窝小猪4对，分别随机分为实验组和对照组。

Methods:4 pairs of littermate swines were allocated randomly to 2 groups(the control group and the experimental group).

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同一胎生的幼崽即被称作同窝出生者(litter mate)。

The pups in a litter are called litter mates.

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它们和同窝的伙伴，也和年长一些的兄弟姐妹一起玩，蹑手蹑脚地接近对方，然后猛扑上去。

The pups will play with each other and their older brothers and sisters, stalking and pouncing on each other.

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