Abstract: In dairy production, the calving interval of dairy cows affects the fecundity of dairy cows, and then affects the economic benefits of dairy farming, and in the actual dairy farming process, there are many factors that affect the calving interval of dairy cows, farmers should start from many aspects, strengthen feeding management to control the calving interval of dairy cows, so as to achieve the purpose of improving the calving interval of dairy cows.

       The general interval between calving of cows is365Day, of which280Day for the gestation period,85day is the breeding period, and the lactation period is305days, the dry milk period is60Days, the ideal production state of cows is one calf a year. Dairy cattle breeding only meet the above indicators to meet the breeding standards, which can ensure good economic benefits.

 Factors affecting calving interval

       There are many factors in the breeding production of dairy cows will affect the calving interval time, mainly due to the lack of feeding and management of dairy cows, inappropriate breeding environment, poor postpartum care and so on. Dairy cows are afraid of heat but not cold. Under the high temperature environment in summer, dairy cows are prone to heat stress. When dairy cows suffer from heat stress, their reproductive function is damaged, and their metabolic function and endocrine function are disordered, which makes ovulation and estrus abnormal, resulting in lower mating conception rate. Heat stress in cows is not conducive to the implantation and development of fertilized eggs, which will increase the probability of abortion and prolong the interval between calving.

Lack of nutrition or insufficient nutrition will lead to reproductive disorders in dairy cows. Inadequate feeding and management of dairy cows will lead to poor physical fitness of dairy cows, reduced resistance, and susceptibility to diseases, which will affect the normal estrus of dairy cows, so that dairy cows cannot be normal. Time mating affects the interval between calves. In addition, after calving, if the nursing is not in place, the cow's physique can not be well recovered, the reproductive function is blocked, and it is easy to suffer from a variety of reproductive diseases, thus delaying or not estrus, and then prolonging the interval between calving.

Rocky Lick Brick

Ways to shorten the interval between calving

       provide suitableNutrition. Nutritional level is an important factor affecting the calving interval of dairy cows. It is necessary to provide appropriate nutritional level for dairy cows to ensure adequate and reasonable intake of nutrients. Dairy cows have different nutritional requirements in different growth stages, physiological states, and different lactation stages, so the nutrition provided is also different. Farmers need to adopt scientific feeding methods to provide reasonable nutrition according to the growth characteristics of dairy cows. In addition to meet the energy, protein, minerals, vitamins and other nutrients, but also to meet the supply of trace elements, crude fiber and other nutrients.

When the cow protein is insufficient, it will cause metritis, vitamin deficiency will lead to long-term non-estrus, crude fiber deficiency will just lead to the afterbirth and so on. Especially in the recovery period of postpartum physique and reproductive function of dairy cows, more attention should be paid to the supply of nutrients, and serious weight loss should be prevented during the lactation period of dairy cows. Cows in the early stage of lactation appetite has not recovered, but because of the increased demand for nutrition, at this time there will be a negative balance of nutrition, in order to ensure that cows get adequate nutrition, can be appropriate to increase the nutrient concentration of the diet, to ensure adequate intake of nutrition, to ensure that cows can normal ovulation, estrus, breeding.

       Provide a suitable breeding environment. Suitable breeding environment can improve the comfort of dairy cows, but also avoid the environment is not suitable for the adverse factors. Cow house is required to maintain a suitable temperature to prevent the impact of bad temperature on cows, and to do a good job of heatstroke prevention and cooling in summer to avoid heat stress in cows. Control the feeding density of dairy cows, pay attention to the daily cleaning and regular disinfection of dairy cows, especially before and after delivery and during milking, to do a good job of cleaning and disinfection of the hindquarters, to avoid dairy cows by bacteria and germs and infection of reproductive system diseases, thus affecting the estrus breeding.

 Strengthen the health management of dairy cows. The health level of dairy cows is the main factor affecting the 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 of dairy cows. Degree and disease resistance, to prevent dairy cows from being invaded by pathogenic microorganisms, which can cause reproductive system diseases such as mastitis and metritis.

       Do a good job of cow delivery and postpartum care. Cows should be prepared before giving birth. Strengthen disinfection, including the hindquarters and vulva of cows, the hands and arms of delivery personnel, and some utensils used in delivery should be thoroughly disinfected to prevent bacterial infection. For dystocia cows to scientific midwifery, reduce the reproductive tract damage caused by dystocia. Cows should strengthen management and do a good job of nursing after delivery. Postpartum can not be fed immediately, to feed some warm water and bran water. The birth canal injury caused by childbirth should be treated in time to avoid infection.

Do a comprehensive monitoring of postpartum diseases of cows, and record them at the same time, including delivery, the discharge of lochia and the time of the first estrus. It is necessary to let the postpartum cows exercise to promote the discharge of lochia and the recovery of physical fitness. A rectal examination of the cow was performed half a month after delivery to observe the recovery of the uterus and ovaries of the cow. If the cow at this time the occurrence of reproductive system diseases should be targeted and timely treatment, so that the cow's reproductive function can be quickly restored, to prevent the impact of the cow's normal estrus, ovulation, breeding, conception.

Do a good job in the management of dairy cattle breeding. The quality of bull semen has an important influence on the calving interval of dairy cows, so we should do a good job in the selection and breeding of dairy bulls. Strengthen the feeding management of dairy bulls and improve the quality of semen. Master the estrus regularity and estrus symptoms of cows, and do timely breeding. Strengthen the artificial insemination technology, the correct operation of insemination methods, to test the quality of semen before mating, the semen to the appropriate location, in order to improve the mating conception rate.

Do a good job in the early pregnancy diagnosis of cows, and make up for the cows with pregnancy failure in time. Do a good job of pregnant cows to protect the fetus, to ensure the normal growth and development of the fetus. For postpartum estrus abnormal cows to take effective measures to promote estrus, through the injection of pregnant horse serum gonadotropin for aphrodisiac. Cows that are still not in heat after treatment should be eliminated in time.