1. Influencing factors of calving interval
Many factors are affecting the calving interval in the production of dairy cows, mainly due to inadequate feeding and management of dairy cows, inappropriate breeding environment, poor postnatal care and so on. Dairy cows are cold-resistance and not heat-resistance. Under the high-temperature environment in summer, dairy cows are prone to heat stress. When heat stress occurs, reproductive function is damaged, metabolic function and endocrine function of the body are disordered, which makes ovulation and estrus abnormal, leading to the reduction of the rate of mating and conception. Heat stress in dairy cows is not conducive to the implantation and development of fertilized eggs, which increases the probability of abortion and prolongs the calving interval. Lack of or inadequate nutrition will lead to reproductive disorders in dairy cows, and inadequate feeding and management of dairy cows will lead to the poor physique, reduced resistance, susceptibility to diseases, and affect the normal oestrus of dairy cows, so that dairy cows can not breed at normal time, affecting the calving interval.
Besides, after calving, if the nursing is not in place, the cow's physique can not be well restored, reproductive function is blocked, and many reproductive diseases are prone to occur so that estrus is delayed or estrus is not established, and then the calving interval is prolonged.
2. Ways to shorten calving interval
Provide appropriate nutrition.
The nutritional level is an important factor affecting the calving interval of dairy cows. It is necessary to provide an appropriate nutritional level for dairy cows to ensure that they have adequate and reasonable nutrient's intake. Dairy cows have different nutritional requirements in different growth stages, physiological states, and lactation stages. Therefore, the nutrition provided is different. According to the growth characteristics of dairy cows, farmers need to adopt scientific feeding methods to provide reasonable nutrition. In addition to energy, protein, minerals, vitamins, and other nutrients, but also to meet the supply of trace elements, crude fibers, and other nutrients.
When the cow protein deficiency will lead to uterine inflammation, vitamin deficiency will lead to long-term estrus cows, and crude fiber deficiency will lead to placenta infertility. Especially in the recovery period of the postpartum constitution and reproductive function of dairy cows, more attention should be paid to the supply of nutrition to prevent serious weight loss of dairy cows during lactation. The appetite of dairy cows has not been restored at the early stage of lactation, but due to the increasing demand for nutrition during milk production, there will be a negative nutritional balance. To ensure adequate nutrition for dairy cows, the nutritional concentration of the diet can be increased appropriately to ensure adequate nutritional intake and normal ovulation, estrus, and mating of dairy cows.
3. Provide a suitable breeding environment.
The appropriate breeding environment can improve the comfort of dairy cows, and avoid harmful factors because of an unsuitable environment. Cowshed requires keeping an appropriate temperature to prevent the influence of bad temperature on dairy cows. It is necessary to do a good job in summer to prevent heat stress in dairy cows. Control the feeding density of dairy cows, pay attention to daily sanitary cleaning and regular disinfection of cowshed, especially before and after childbirth and during milking, do a good job of cleaning and disinfection of the hindquarters to avoid the dairy cows infected with reproductive system diseases by bacteria and pathogens, thus affecting estrus mating.
4. Strengthen the health management of dairy cows.
The health level of dairy cows is the main factor affecting calving interval. Therefore, farmers and farms should do a good job in the health defense of dairy cows. In addition to strengthening daily environmental management and doing a good job in sanitary cleaning and disinfection. They should also formulate scientific and reasonable immunization procedures, and strictly implement them to improve the health and disease resistance of dairy cows, to avoid the invasion of pathogenic microorganisms on dairy cows which causes diseases of the reproductive system such as mastitis and uteritis.
5. Do a good job of dairy cow delivery and postpartum care.
Dairy cows should be prepared before delivery. Strengthen disinfection, including the hind body and vulva of dairy cows, hands and arms of midwives and some utensils for delivery should be thoroughly disinfected to prevent the occurrence of bacterial infections. For dairy cows with dystocia, scientific midwifery is needed to reduce reproductive tract damage caused by dystocia. Dairy cows should strengthen management and do a good job of nursing after delivery. Don't feed cows immediately after delivery. Feed warm water and bran water. The obstetric tract injury caused by childbirth should be treated in time to avoid infection. Do a good job of comprehensive monitoring of postpartum diseases in dairy cows, while recording, including delivery, lochia discharge and the first estrus time. Postpartum dairy cows should exercise to promote lochia excretion and physical recovery. To observe the recovery of uterus and ovary of dairy cows, the rectal examination was carried out half a month after delivery. If the disease of the reproductive system occurs in cows at this time, it should be dealt with in time, so that the reproductive function of cows can be quickly restored, and the normal estrus, ovulation, mating, and conception of cows can be prevented.
6. Do a good job of dairy cow breeding management.
The semen quality of breeding bulls has an important influence on the calving interval of dairy cows, so the breeding of dairy bulls should be done well. Strengthen the feeding and management of dairy bulls to improve the quality of semen. Master the oestrus regularity and oestrus symptoms of cows to achieve timely mating. Strengthen the technology of artificial insemination, and correctly operate the method of insemination. Before mating, farmers should check the quality of semen and transport semen to the appropriate position to improve the fertility rate of mating. Do a good job in early pregnancy diagnosis of cows, and timely supplementary matching the cows of pregnancy failure. Do a good job of pregnant dairy cow fetal protection to ensure the normal growth and development of the fetus. Effective measures should be taken to promote estrus in cows with abnormal postpartum estrus. Estrus can be induced by injecting serum gonadotropin of a pregnant horse. Cows that still do not oestrus after treatment should be eliminated in time.