Breeding techniques of Dairy cows

After a high degree of breeding and breeding of excellent varieties of dairy cows, the dairy cows in China are mainly black and white dairy cows. in order to enable the cattle to reproduce normally, it is necessary to understand the reproductive physiology of the cows and carry out scientific feeding and management in the production practice. to ensure the normal estrus and breeding of cattle, let's take a look at the reproduction technology of dairy cows.

Time of sexual maturity of dairy cattle

1. Sexual maturity: sexual maturity means that the sexual organs and secondary sexual characteristics of domestic animals are well developed, and the ovaries of cows can produce mature eggs. The bull's testicles produce mature sperm and have normal sexual behavior. After mating, the cow can be fertilized and can complete the process of pregnancy and embryonic development. The age of sexual maturity of dairy cows is usually 8 ~ 12 months old. However, cattle can not be mated immediately after sexual maturity, because it is still in the process of growth and development. at this time, mating not only affects the growth and development of cattle and the later production performance, but also affects the healthy growth of calves. You can't breed until the cow is mature.

2. Physical maturity: physical maturity means that the bones, muscles and internal organs of bulls and cows have basically developed, and have the shape and structure that they should have at maturity. Body maturity is later than sexual maturity, and when the cow's body weight reaches about 70% of the adult cow's body weight, it reaches body maturity and can begin to mate. On the one hand, the sexual and physical maturity of cattle depends on age, and at the same time, it is related to breed, feeding management, climatic conditions, sex and ontogeny. General small breeds are earlier than large breeds, and good breeding and management conditions are earlier than poor ones. The climate in warm areas is earlier than that in cold areas, so it is necessary to be flexible in determining the first mating of cows. The first mating age of dairy cows is generally 1.5-2 years old, but it is not too late to mate, which often causes difficulties in later breeding and affects production.

The estrous cycle of a cow

1. Estrus characteristics: after sexual maturity, a series of sexual activities begin to occur periodically in cows, such as mucous membrane congestion, edema, mucus excretion, mental excitement, sexual desire, acceptance of other cattle, ovarian follicular development and ovulation, etc., internal and external physiological activities are called estrus, and the stage of concentrated expression of estrus is called estrus, the period from one estrus to the next. It's called an estrous cycle.

2. Duration: the duration of estrus refers to the time that the cow accepts climbing to avoid climbing. The duration of oestrus in cows is short, with an average of 18 hours, ranging from 6 to 36 hours, and some cows are as long as 48 hours. Because the duration of oestrus of the cow is short, and now it is artificial insemination, therefore, we should pay attention to observe the estrus of the cow, so as not to miss the estrus and lose the opportunity to breed. Cows ovulate mostly at night. It is necessary to master its characteristics, grasp the time of timely insemination, and improve the success rate of insemination.

3. Estrous cycle: the average estrous cycle of cows is 21 days. Estrus is affected by light, temperature, feeding and management, individual conditions and other factors, there is a range of variation, the range of change is 17-25 days. Estrus is proestrus, estrus, metestrus and diestrus.

① proestrus: proestrus is the preparatory period of estrus, vaginal secretions gradually become thin from dry sticky state, secretions increase, reproductive organs begin to congestion, but do not accept other cattle to climb across, this period lasts for 4-7 days.

② estrus: estrus is the peak sexual desire of the cow, the performance of loss of appetite, mental excitement, often mooing, tail root raised, willing to accept the climb of other cattle. The vulva is red and swollen, a large amount of sticky transparent fluid flows out from the vulva, the vaginal mucosa is red and shiny, and mucus secretion increases. In the herd, some cattle often smell the vulva of the cow in estrus.

③ metestrus: metestrus is the period when the estrus phenomenon gradually disappears. The cow's sexual desire disappears and refuses to climb. Vaginal secretions decreased, vaginal mucosal congestion and swelling gradually subsided, and the duration of metestrus was 5-7 days.

④ diestrus: diestrus is also known as diestrus, during which the corpus luteum gradually disappears and the follicles gradually develop to the next sexual cycle. The duration of the diestrus period of the cow is 6-14 days. After mating, the cow becomes pregnant, which is called pregnancy. The periodic corpus luteum changes to pregnant corpus luteum and no more estrus occurs before calving.

Estrus Identification of cows

1. External observation

① estrus duration: in the early days, cows are excited, howling, walking, loss of appetite, crawling and running, and it is still early to breed. In the middle stage, the cow is allowed to climb and spread its hind legs, which should be matched every other day. At the end of the year, the cow gradually quieted down, and the bull still followed and sniffed. When the bull climbed, the cow dropped and refused to climb, but seldom ran, so it was a good time to breed.

Degree of external swelling of ②: the vulva begins to swell and turn red in the early stage of estrus, and the vulva is swollen and shiny in the middle of estrus. It is still early to breed at this time. When the swelling basically disappears and the vulva appears wrinkles, it is the mating period.

③ mucus character: when the cow is in estrus, the mucus that flows out from the vagina can be called estrus, and the estrus is produced to the end, from the color point of view, from green to yellow or clear white, from the viscosity point of view, its tractive nature is from small to big, and then from big to small, the result is to see the yellow short-term or white short-term breeding.

④ cervical changes: the cervix of the cow is relatively hard during the diestrus, and the rectal touch has a sticky sensation. With the extension of the duration of estrus, the cervix changes from hard to soft and thicker, and the external cervical mouth at the end of estrus changes from soft to hard, but the inner mouth is still soft, mating is the most suitable.

⑤ cows tend to show excitement during estrus, loss of appetite and milk, tail root raised, chase and climb over other cows and accept it. The difference between the two is that if the cow is in estrus, it will stand still and raise its tail at the same time, and if it is not a cow in estrus, it will often escape with its back arched. When the estrus cow climbs over the other cattle, the vulva twitches and drips urine, with the action of a bull mating. The vulva is red and swollen and mucus flows out of the vulva.

2. Estrus test: one is to put the vasectomized bull into the cow herd, test the estrus in the herd during the day, separate the male and female at night, and judge the oestrus of the cow according to the situation of the bull chasing and the degree to which the cow accepts the climb. The other is to put the trial bull close to the cow, such as the cow likes to rely on the bull, and bend and bow back posture, indicating that it may be in estrus.

3. Vaginal examination: vaginal examination uses vaginal opener to observe the changes of vaginal mucosa, secretion and cervix to judge whether it is in estrus or not. The vaginal mucosa of the estrous cow is congested and flushed, and the surface is smooth and moist. The external mouth of the cervix is congested, relaxed, soft and open, excreting a large amount of transparent tractive mucus, such as glass rod (commonly known as hanging line), which is not easy to break. The mucus is thin at first, but gradually thickens with the lapse of time, and the amount of mucus changes from less to more. To the later stage of estrus, the amount decreases gradually and the stickiness is poor, the color is opaque, sometimes contains yellowish cell debris or trace blood. The non-estrous cow's vagina is pale and dry, and the cervix is closed, so there is no mucus outflow.

4. Rectal examination: the estrus period of cows is short (12-18 hours). Generally, they can breed 1 or 2 times during estrus. Rectal examination is not necessary to determine the time of ovulation. However, in some malnourished cows, the reproductive function declines and the follicles develop slowly, so the time of ovulation will be delayed, and some cows may ovulate earlier and irregularly. But most of them are slow follicular development and delayed ovulation. For these cows, it is impossible to correctly judge the time of ovulation without rectal examination. In order to correctly determine the appropriate time for mating, in addition to external observation, it is also necessary to conduct rectal examination. Through rectal palpation, the development of follicles can be divided into four stages.

① follicle appearance period: the follicle was slightly enlarged, the diameter of the follicle was 0.5cm to 0.75cm, and it was a softening point during palpation, and the fluctuation was not obvious. During this period, the general cattle began to show estrus.

② follicular development stage: follicles enlarged to 1cm-1.5cm, showing a small ball, obvious fluctuations, in the second half of this period, the performance of oestrus is not significant.

③ follicle maturation stage: the follicle is no longer enlarged, but the follicular wall becomes thinner and the tension increases. During rectal examination, there is a sense of rupture at a touch.

④ ovulation period: follicular rupture ovulation, follicular fluid loss, so the follicular wall becomes soft, becoming a small depression. 6-8 hours after ovulation, the corpus luteum begins to form and the depression can no longer be touched. Ovulation usually occurs 10-15 hours after the disappearance of libido. There is more ovulation at night than in the day, and more ovulation in the right ovary than in the left.