1. Health status
Before mating, dairy cows must be checked to ensure that they are healthy and disease-free, and their reproductive organs and ovulation physiological activities are normal. Some dairy cows are physically healthy on the surface, but their reproductive organs suffer from diseases such as ovarian inflammation, chronic uteritis and ovarian cysts, which make it difficult to conceive. When dairy cows suffer from these diseases, the combination of local and systemic treatment can be chosen. For example, when dairy cows suffer from chronic endometritis and cause repeated sterility, they can be injected with Chinese and Western medicines with the function of clearing the official and eliminating inflammation into the uterus, and then artificial insemination is carried out after their complete recovery, to improve the fertility rate. If cows suffer from ovarian cysts, progesterone or chorionic gonadotropin should be used for treatment, which has a very obvious therapeutic effect.
2. Nutrition level
During the daily feeding and management of dairy cows, if they ingest too much nutrition or lack nutrition, they can cause reproductive diseases. Especially before and after delivery, if the fed diet contains less energy and protein, it will prolong the time needed for uterine recovery, and some dairy cows will also have uterine inflammation, thus affecting the normal physiological function of the ovary. In the dietary composition of dairy cows, if there are less macroelement, trace elements, and vitamin A and vitamin E deficiency, it will lead to false oestrus, long-term estrus or irregular oestrus and can not accurately judge the oestrus.
Besides, the lack of nutrients in dairy cows can also cause abnormal ovulation. Sometimes, although they can ovulate, due to insufficient nutrients' intake, fertilized eggs can not be implanted, or early embryo death occurs. Moreover, if the diet of dairy cows lacks crude fiber, it can not only cause abnormal metabolism of cattle but also make it unable to give birth smoothly during production, so that it can cause diseases after delivery. If frozen, spoiled and moldy forage is added to the diet of dairy cows, it will cause long-term estrus or repeated sterility after feeding. Therefore, in the daily management and feeding of dairy cows, it is necessary to design a balanced diet formula with full nutrition, and pay attention to the rational mixing of concentrate and roughage in the feeding process, and mix well before feeding.
3. Estrus identification and mating time
The commonly used methods of estrus identification in dairy cows include external observation, rectal examination, estrus test, and vaginal examination. However, due to the short duration of estrus and the obvious external characteristics of dairy cows, clinical estrus identification usually combines external observation and rectal examination, which can correctly judge whether the cows are estrus or not, and determine the appropriate mating time. When the rectal examination is taken, the requirement is high, and after mastering it skillfully, the higher accuracy of identification can be obtained. However, we should pay attention to the identification of luteal and follicle when taking the rectal examination for estrus identification, to make accurate estrus judgment and correct pregnancy diagnosis, thus ensuring that dairy cows can mate in time after estrus, and avoiding mismatching of pregnant dairy cows causing abortion.
Dairy cows usually begin ovulation about 10 hours after estrus, so they can inseminate within 13-18 hours before ovulation. If the calculation is based on the presence of standing estrus in dairy cows, insemination should be arranged 5 to 9 hours after the occurrence of standing estrus. If the dairy cows begin to have oestrus, insemination is suitable for 11-16 hours after the onset of oestrus. However, it should be noted that the specific time of insemination also needs to be judged according to the results of estrus identification of dairy cows. Generally speaking, dairy cows have estrus in the morning and can be inseminated in the afternoon or evening of that day. Estrus in the afternoon, especially in the evening, can be inseminated on the morning of the second day. To improve the conception rate of dairy cows, two inseminations can be carried out in one estrus period, and the second insemination can be carried out after 8-l0 hours.
4. Semen quality and insemination techniques
The conception rate of dairy cows is largely determined by the quality of semen. The better the quality of semen, the higher the conception rate. Therefore, we should strictly follow the principle of semen treatment, that is, the quality of fresh semen is not good enough to be frozen, and the vitality of frozen semen is not good enough to be stored. During insemination, it is necessary to ensure that sperm motility meets the criteria, which is more than 0.35. If semen does not meet the requirements, it must be discarded and cannot be used for insemination. The extraction and thawing of frozen semen should be carried out in strict accordance with the operating specifications. The storage time should not be too long, and it is best to be ready-to-use.
The key link of artificial insemination of dairy cows is insemination technology. Its operation must be accurate, meticulous, strict, and thoroughly disinfected. If the operation is not standardized, the conception rate of dairy cows will be seriously affected. When using rectum to grasp cervical insemination in dairy cows, attention should be paid to slow insertion, moderate depth, light injection, and slow outflow to avoid semen reflux. When semen is injected, the hand extending into the rectum can press the uterus down slightly, making the deferens slope from back to front, which is conducive to the flow of semen into the uterus.
Temperature varies in different seasons, and the estrus behavior of dairy cows is largely affected by temperature changes. When the climate is cold, cows can oestrus, but there is no obvious external manifestation, there will be no obvious phenomenon of climbing across, oestrus is very easy to be ignored, leading to the loss of mating rate. Besides, in the poor conditions of the mating room for mating or thawed semen to other places for insemination, resulting in frozen semen thawed by obvious temperature stimulation will seriously affect the fertility rate of the mating. Moreover, the hot summer climate and high temperature will also affect the oestrus performance of dairy cows and reduce the fertility rate, which is mainly due to the high-temperature environment that will significantly increase their body temperature, resulting in endocrine dysfunction.
According to statistics, dairy cows can get a higher conception rate by breeding in April-June, but the conception rate by breeding in November-December and January-February is lower. To alleviate the influence of temperature on the conception rate of dairy cows, a standardized breeding room can be built to ensure that the temperature of the breeding room can be maintained in the range of 10-20℃. At the same time, semen thawing should strictly abide by the operating rules, and make the thawed semen pass through the harmful temperature zone quickly.