春天是很多动物繁殖的季节。

Chūntiān shì hěn duō dòngwù fánzhí de jìjié.

Spring is the breeding season for many animals.

这种鱼在人工环境下很难繁殖。

Zhè zhǒng yú zài réngōng huánjìng xià hěn nán fánzhí.

This type of fish is very difficult to breed in an artificial environment.

经过多年繁殖，这个农场的牛群数量翻了一倍。

Jīngguò duō nián fánzhí, zhège nóngchǎng de niú qún shùliàng fān le yī bèi.

After years of breeding, the number of cattle on this farm has doubled.