Sexual maturity time of dairy cows
1. sexual maturity: sexual maturity means that the sexual organs and secondary sexual characteristics of livestock are well developed, and the ovaries of cattle can produce mature eggs. Bull testicles can produce mature sperm and have normal sexual behavior. Cows can be fertilized after mating to complete the process of pregnancy and embryo development. The age of sexual maturity of dairy cows is generally 8~ 12 months old. However, after sexual maturity, cattle cannot reproduce immediately because they are still in the process of growth and development. Breeding at this time not only affects the growth and development of cattle and the performance of future production, but also affects the healthy growth of calves. Don't breed until the cows are mature.
2. Somatic maturation: Somatic maturation means that the bones, muscles and internal organs of bulls have basically developed, and they have appropriate shapes and structures when they mature. Physical maturity is later than sexual maturity. When the weight of a cow reaches about 70% of that of an adult cow, it reaches physiological maturity and can begin to reproduce. The sexual maturity and physical maturity of cattle depend on age, breed, feeding management, climatic conditions, gender and individual development. Generally, small varieties are earlier than large varieties, and the good feeding and management conditions are earlier than the bad ones. The climate in warm areas is earlier than that in cold areas, so it is necessary to be flexible in determining the initial breeding of dairy cows. The first mating age of dairy cows is generally 1.5~2 years old, but it should not be too late to mate, which often causes difficulties in later mating and affects production.
Estrus cycle of dairy cows
1. Estrus characteristics: After sexual maturity, cows begin to have a series of sexual activities periodically, such as congestion, edema, mucus excretion, mental excitement, increased sexual desire, climbing from other cows, follicular development, ovulation and so on. Internal and external physiological activities are called estrus, and the stage of concentrated expression of estrus symptoms is called estrus. The period from one estrus to the next is called estrus.
2. Duration: Estrus duration refers to the time that cows accept to avoid climbing. The duration of estrus of dairy cows is short, with an average of 18 hours, ranging from 6 to 36 hours, and the length of individual dairy cows reaches 48 hours. Because the estrus of cattle is short, it is artificial insemination now. Therefore, we should pay attention to observing the estrus of cattle so as not to miss the estrus and lose the mating opportunity. Most cows ovulate at night. It is necessary to master its characteristics, grasp the appropriate insemination opportunity and improve the success rate of one insemination.
3. Estrus cycle: The average estrus cycle of dairy cows is 2 1 day. Estrus is affected by light, temperature, feeding management, individual conditions and other factors, and the range is 17-25 days. Estrus is divided into pre-estrus, estrus, post-estrus and estrus.
Preestrus: Preestrus is the preparation period of estrus. Vaginal secretions gradually become thinner from a dry and sticky state, secretions increase, and reproductive organs begin to congestion, but other cows are not allowed to climb over. This period lasts 4~7 days.
Estrus: Estrus is a period when cows have strong sexual desire, which is characterized by loss of appetite, mental excitement, frequent Cleisthenes barking, tail root sticking up, and willingness to accept other cows to climb mountains. The vulva is red and swollen, a large amount of viscous transparent liquid flows out from the vulva, the vaginal mucosa is flushed and shiny, and mucus secretion is increased. In the herd, some cows often smell the genitals of cows in estrus.
Late estrus: Late estrus is the period when estrus gradually disappears. The cow lost its libido and refused to climb. Vaginal secretions decrease, and the congestion and swelling of vaginal mucosa gradually subside, and the duration of late estrus is 5-7 days.
Resting period: Resting period is also called intersexual period. During this period, corpus luteum gradually disappears and follicles gradually develop into the next sexual cycle. The estrus of cattle is 6- 14 days. After mating, cow B.
Estrus duration: At the beginning, cows were excited, howling, wandering and lost appetite. They can crawl and run. It's too early to breed. In the middle stage, cows will crawl over, spread their hind legs and mate the next day. At the end of the semester, the cows gradually quieted down, and the bulls were still sniffing behind. When the bull climbs, the cow loses weight and refuses to climb, but rarely runs. Breeding is just right at this time.
Extinction of swelling: Cows' pudendal parts begin to swell and turn red in the early estrus, and obviously shine in the middle estrus. At this time, it is still early from the breeding period. When the swelling basically disappears and the genitals appear wrinkles, it is the mating period.
Mucus characteristics: the mucus flowing out of the vagina during estrus of dairy cows can be called estrus fluid. From the beginning to the end, the estrus fluid changes from green to yellow or white, and its traction force changes from small to large, and then from large to small from viscosity. Therefore, yellow or white short lines breed.
Changes in the cervix: When cows are in estrus, the cervix is hard and the rectum feels like a glue stick. With the extension of estrus, the cervix changes from hard to soft and becomes thicker. At the end of estrus, when the external opening of the cervix changes from soft to hard, but the internal opening of the cervix is still soft, it is most suitable for breeding.
When cows are in estrus, they tend to show excitement and anxiety, reduce appetite and milk production, raise tail roots, chase and climb other cows, and accept other cows to climb. The difference between the two is that if the cow is in heat, it will stand still and hold its tail; If it is not in heat, it will often run away with its back hunched. When a cow crawls over other cows in estrus, the vulva twitches, drops of urine, and there is the action of bull mating. The vulva is red and swollen with mucus flowing out of the vulva.
2. Emotional test method: one is to put the bulls with vasectomy into the herd and put them into the herd during the day to test estrus. At night, males and females are separated, and cows are judged to be in estrus according to the chasing and climbing situation of bulls and the degree to which cows accept climbing. The other is to let the bull approach the cow. For example, the cow likes to lean on the bull and make a bow gesture, indicating that it may be in heat.
3. Vaginal examination: Vaginal examination is to observe the changes of vaginal mucosa, secretion and cervix with vaginal mouth opener to judge whether it is estrus. During estrus, the vaginal mucosa of dairy cows is congested and flushed, and the surface is smooth and moist. The external cervix is congested, loose and soft, and a large amount of transparent mucus, such as a glass rod, is discharged, which is not easy to break. At first, the mucus was very thin, and gradually became thicker as time went on, and the amount changed from less to more. In the late estrus, the amount gradually decreases, the viscosity is poor, the color is opaque, and sometimes it contains light chlorine-producing cell fragments or trace blood. In estrus, the vagina of dairy cows is pale and dry, the cervix is closed, and no mucus flows out.
4. Rectal examination: The estrus time of cows is short, and generally 1~2 estrus is enough. There is no need to use rectal examination to determine ovulation time. However, some malnourished cows have decreased reproductive function and slow follicular development, so the ovulation time will be delayed. Some cows may ovulate earlier and ovulate irregularly. But most of them are slow follicular development and delayed ovulation. For these cows, it is impossible to correctly judge the ovulation time without rectal examination. In order to correctly determine the suitable breeding period, besides external observation, rectal examination is also necessary. Follicle development can be examined by rectal palpation, which is divided into four stages.
Follicle appearance: the follicle is slightly enlarged, with a diameter of 0.5~0.75cm, and its softening point is not obvious when palpated. During this period, the average cow has already begun to estrus.
Follicle development period: Follicle grows to 1~ 1.5cm, which is spherical and obviously undulates. In the second half of this period, estrus performance is not significant.
Follicle maturation: Follicles no longer grow, but the wall of follicles becomes thinner and the tension increases. During rectal examination, there is a feeling of breaking at the touch.
Ovulation period: follicular rupture ovulates and follicular fluid is lost, so T.