cow in estrus

例句：

1. 1. The cow is in the estrus stage, which means it is ready to breed.
   这头牛正处于发情期，意味着它准备好繁殖了。
2. 2.During the estrus period, the cow's behavior can change significantly.
   在发情期，奶牛的行为会有很大变化。
3. 3.She decided to take advantage of the estrus cycle to breed her cows.
   她决定利用发情周期来繁殖她的奶牛。