Early estrus. Cows just started estrus, the symptoms are chirping, getting lost, walking along the playground, trying to get close to other cows; Crawl over other cows; The vulva is slightly swollen, and the mucosa is moist and flushed; Sniffing the hindquarters of other cows, unwilling to accept other cows crawling over; Milk production has declined. ?

2. Estrus peak (lasting about 18 hours). It is characterized by standing and accepting other cows to climb and climb over other cows; Frequent singing and excitement; Loss of appetite or refusal to eat; Milk production has dropped. ?

3. Estrus is almost over. Cows refuse to accept other cows to crawl and smell other cows; Trying to climb over other cows; Normal appetite and increased milk production; May excrete mucus from the vulva. ?

The change of symptoms in estrus is a gradual process, and there are individual differences in the length of estrus. The suitable breeding time should be shortly after the end of the estrus period of dairy cows. According to experience, generally estrus in the morning and mating in the afternoon; Or estrus in the afternoon and mating the next morning. When the weather is hot in summer, the breeding time should be appropriately advanced and slightly delayed in winter. Old and frail cows have short estrus duration and early ovulation, so they should be bred early; Heifer's oestrus lasts longer and ovulation is later, so it is necessary to breed later. Usually, it is enough to master the appropriate breeding and lose the sperm once. As long as the delayed ovulation is diagnosed by touching the follicle through rectal examination, a second insemination is needed.