First, the breeding of dairy cows

In order to enable the cow to reproduce normally, it is necessary to understand the reproductive physiology of the cows and to conduct scientific feeding and management of the cows in the production practice so as to ensure the normal estrus and breeding of the cows.

(1) Sexual maturation and initial age of dairy cows

Sexual maturation refers to the development of the sexual organs and secondary sexual characteristics of livestock. The ovaries of cows produce mature eggs; the testicles of bulls produce mature sperm and have normal sexual behavior. After mating, the cow can be fertilized and can complete the pregnancy and embryonic development process. The age of sexual maturity of cows is generally between 8-12 months of age. However, after sexual maturity, cattle cannot be bred immediately, because it is still in growth and development. At this time, breeding will not only affect the growth and development of the cattle and the subsequent production performance, but also affect the healthy growth of the yaks. Mature can be reared.

Body maturation refers to the fact that the skeletons, muscles, and internal organs of male cows have been basically completed and have the form and structure that they should have when they mature. When the body matures later than the sexual maturity, when the cow's body weight reaches about 70% of the weight of the adult cow, the body matures and the breeding can begin. The sexual maturation and body maturation of cattle depends on their age and on species, feeding and management, climate conditions, gender, and individual development. Generally, small breeds are older than large breeds, and the conditions for good rearing are earlier than poor. The warm area is earlier than the cold area, so it is necessary to determine the initial allocation of the cow. The initial mating age of dairy cows is generally between 1.5 and 2 years old, but mating should not be too late, too late will often result in difficulties in rearing, which will affect production.

(b) Cow's estrus

After sexual maturity, the cow begins to periodically undergo a series of sexual activities such as congestion, edema, exudation of mucous, mental excitement, sexual desire, other cattle's crawling, ovarian follicle development, and egg discharge. . The above-mentioned internal and external physiological activities are called estrus; the stage of concentrated expression of estrus symptoms is called estrus. The period from the beginning of one estrus period to the beginning of the next estrus period is called an estrus cycle.

The estrus cycle of cows averaged 21 days. The estrus period was affected by factors such as light, temperature, feeding and management, and individual conditions. There was a range of change, ranging from 17 to 25 days. The estrus period was pre-estrus and estrus. Late estrus and recession.

1, pre-estrus: the early stage is the preparation of heat, vaginal secretions from the state of dry sticky gradually become thin, increased secretions, reproductive organs began to congestion, but do not accept other cattle to climb across, the duration of this period is 4 - 7 days.

2, estrus period: estrus is a period of strong cow libido, the performance of the loss of appetite, mental excitement, often barking, tail raised, willing to accept other cattle to climb. The vulva is red and swollen. A lot of viscous transparent fluid flows from the vulva, the vaginal mucous membrane is flushed and shiny, and mucus secretion increases. There are often cows in the herd that sniff the cow's genitals.

The duration of estrus refers to the time the cows accept the climb to avoid the climb. The short duration of estrus in cows is generally 18 hours on average. The range is 6-36 hours, and individual cows reach 48 hours. Since the cow's estrus has a short duration and is now artificially inseminated, it is important to observe the estrus of the cows so that they do not miss the opportunity to miss the estrus period. The ovulation of cows is mostly at night. To grasp its characteristics, grasp the timing of timely insemination, improve the success rate of an insemination.

3, late estrus: is the period when the estrus phenomenon gradually disappears. Cow libido disappeared and refused to climb. Vaginal secretions decreased, and the state of congestion and swelling of the vaginal mucous membranes gradually subsided. The duration of late estrus was 5-7 days.

After 2 to 3 days after cows' estrous run, the cows shed blood or mixed mucus from the vagina. If the amount of bleeding is small and the color is normal, there is no adverse effect on bovine pregnancies; if the amount of bleeding is heavy, the color is dark red or dark purple, it is suffering from Symptoms of uterine diseases should be carefully examined and the time must be taken care of. If the treatment is not timely, it will often result in cow infertility.

4. Rest period: Also known as intercourse, the corpus luteum gradually disappears during this period and the follicle develops gradually into a sexual cycle. The duration of the cow's sorrow period is 6-14 days. After mating, the cow is pregnant. This period is called gestation period. The corpus luteum turns into the gestational corpus luteum, and no more estrus occurs until the lower jaw.

(c) Cows first estrus after childbirth

In order to promptly breed the postpartum cows and shorten the calving interval, it is necessary to pay attention to the first occurrence of heat after the cows are born. After the cow undergoes rapid and dramatic changes in pregnancy, childbirth, and reproductive organs, the genitals of the cow have a process of recovery, and the time for the first estrus after birth is inconsistent. Under the conditions of suitable temperature, no post-partum disease, and good husbandry and management, the time for the first occurrence of heat after birth is shorter. Generally in the postpartum 40-45 days heat, and some 25-30 days after the beginning of the first heat. The first estrus time after delivery starts, usually within 20-70 days. If the estrus has not been detected 60-90 days after delivery, the cow's health, nutritional status, ovaries, and uterus should be examined and treated to prevent air and infertility. Some cows are postnatal due to physical weakness, or a large amount of lactation, resulting in ovulation without obvious estrus symptoms of estrus, especially in high-yield cattle, some cattle up to 45%. To estrus In estrus-free cows, ovarian follicular development should be enhanced.

In order to reach a cow's annual birth, it must be conceived within 85 days after birth. During the 20 days after childbirth, a small number of cows returning to estrus and breeding are only 25% fertile. The average fertility rate after mating in 40-60 days is 50%, and the fertility rate after mating is more than 60% after 60 days. . The introduction of post-harvest early mating, while increasing the consumption of semen, is more assured for shorter production intervals and can increase productivity. It is generally considered that estrus breeding is most suitable for 40-50 days after childbirth.

(D) Cow Identification

The purpose of identifying the cow's estrus is to find the cow that is departed, determine the most appropriate breeding time, and increase the rate of conception. Whether or not the household raises estrus to the cow is mainly based on external observation of the cow. According to the cow's mental state, external changes and sticky outflows of the vulva and other judgments. The excitement of the cow's estrus caused excitement in the central nervous system, screaming, bowing, and bowing. The examiner raised his tail without resistance and urinated frequently. Loss of appetite, decreased response, and decreased milk production. These performances progressed with the development of heat, from weak to strong, and weakened at the end of heat.

The cows were estrus, the labia was slightly swollen and moist, and the mucus came out of the vulva. According to the outflow of mucus traits, cows can be determined more accurately. Cows in the early stages of estrus flowed transparently, such as egg whites, and did not show filthy mucus; during the estrus, the mucus was translucent, milky, or white with clipped filaments. Some cows had blood or mixed mucus from the vagina. It is the end of estrus. However, some cows can be pregnant at this time, such as the discharge of mucus was translucent latex, hanging in the vulva or adhering to the hips and tail of the cow, and has a strong toughness for the discharge of pregnant cows Things. Special attention should be paid to the following situations: If a large amount of red stained, slightly stenched liquid is discharged, lochia will be discharged for post-partum cows; for example, a lot of white lumpiness will be discharged, and there will be malodour, which will result in the post-partum rot of cows; Yellowish dirt or semi-filament-thin, white filaments that are unfilamentous are cows with inflammation of the reproductive tract. Found a similar situation, to identify the reasons, take measures to make it back to normal or recover as soon as possible. Most cows are estrus at night. Therefore, careful observation is required when it is dark and when it is dark. The accuracy of judgment is higher.

The estrus performance of the cows is most easily observed at the sports grounds or grazing lands. For example, the cows look up and look forward, they are excited about spirits and go east to the west, sniffing other cows to climb over each other, and the cows being climbed are quiet and their hind legs are apart. And raising the tail, this time is called stabilizing period, is the estrus period; only climbs across other cows and does not accept the climb of other cows, this cow does not have estrus. After the stabilizing period, the estrus cow escapes the climb, but the following cow does not leave. This is the end of the estrus.

In short, breed breeding records and forecasting systems should be established for breeding cows. The date of the next estrus is forecasted based on the number of days recorded and the number of estruss in the cow. Observe the cows that are expected to be in heat and observe carefully and patience. Observe 2-3 times a day so that the cow's estrus does not leak.

Vaginal examinations and rectal examinations are also two commonly used methods to identify whether or not a cow is oestrus. However, these two methods require certain devices and require strict disinfection. Without the experience and the usual identification, it is difficult to obtain correct results if necessary. For cattle in this area, it is best to use a breeder or animal husbandry technician to help with the inspection.

Cows often have abnormal estrus, and cows have some of the following manifestations of abnormal estrus.

1, implicit estrus, also known as latent estrus or quiet estrus, refers to the external performance of cow estrus is not obvious, the lack of performance of sexual desire. However, ovarian follicles develop and ovulate. This situation has a higher proportion in dairy cows and generally occurs in frail old, malnourished, less sunshine, insufficient exercise during the rainy season, or cows with higher milk production. The main cause is endocrine disorder, which causes inadequate secretion of estrogen, or cows are not sensitive to estrogen response and cause no obvious estrus symptoms. This type of cow has short estrus times and is not easy to observe. Loss of production. For estrus, in addition to enhanced observation, rectal examination of ovarian follicular development can help make accurate judgments.

2, wig lover only the external appearance of estrus, but no follicular development, no ovulation called false estrus. Wigs are more common in pregnant and bred cows, cows in the 4 - 5 months of pregnancy, and some 1 - 2 months before the supervision of production, suddenly have sexual desire performance, crawling across other cattle, Especially accept the climb. However, vaginal examination, contraction of the cervix, no estrus mucus; rectal examination can be to the fetus. In bred cattle, cows have a variety of external signs of estrus, but there are no developing follicles in the ovary and do not ovulate.

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