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The milk production performance of dairy cows is influenced by many factors, which are summarized as follows: genetic factors, physiological factors and environmental factors. Genetic factors include species and individuals; physiological factors include age, parity, lactation, dry period, estrus, and pregnancy; environmental factors include feeding and management, milking and breast massage, calving season, outside temperature, and illness. Variety of genetic factors. The milk yield and milk fat percentage of different breeds of cattle differ greatly. After highly cultivated varieties, their milk production is significantly higher than that of local breeds. There is a negative correlation between milk production and milk fat percentage, and the milk yield is higher. The milk fat percentage is correspondingly low, but through planned breeding, the milk fat percentage can also be increased. individual. Individuals within the same breed, although at the same stage of life, the same feeding and management conditions, their milk production and fat percentage are still different. For example, Holstein's milk production varies from 3000 to 1200 kilograms, and the fat percentage ranges from 2.6% to 6.0%. In general, individuals with large body weights have higher absolute milk production than those with smaller body weight. Under normal circumstances, weight of 550-650 kg is appropriate. In addition, individual height, weight, feeding characteristics, personality, etc., can affect the individual's lactation. Physiological factors age and parity. Dairy cows' lactation ability changes regularly with age and parity. The age of first-produced cows is about 2 years old, and because of their still-developing stages, the milk production is low. Later, as the age and parity increase, milk production gradually increases. By the ages of 6-9 and 4-7, the milk production reached the peak of her life. After the age of 10, due to the gradual aging of the body, the milk production gradually declined. However, well-fed and well-established cows maintain a high level of lactation when they reach the age of 13-14. On the contrary, poorly maintained and debilitated cows, after 7-8 years of age, gradually reduce their milk production. . During lactation. Cows start to stop lactation. Milk production changes regularly during lactation: After delivery, daily milk production rises gradually, reaching the maximum from the first lactation month to the second lactation month. peak. After a certain period of time, the fourth lactation month began to decline again. After the 7th lactation month, it rapidly decreased and stopped lactating around the 10th lactation month. The daily milk production during the whole period forms a dynamic curve called the “lactation curve,†which reflects the general pattern of lactation in dairy cows. In the same herd, although environmental conditions are relatively consistent, due to differences in individual genetic traits, there are three types of lactation curves: The first type is highly stable, and the rate of decline in monthly milk production is maintained at an average rate. Within 6%, these individuals have excellent breeding value; the second type is relatively stable, and the rate of monthly milk production decline is 6%-7%. Such individuals are more common in cattle, and have full-lactation output. High milk volume. Therefore, they can be selected into breeding nucleus groups. The third category is a sharp decline in the monthly rate of lactation decline rate of more than 8% on average, this type of individual milk production is low, short lactation period should not be reserved for species use. During different lactation periods, there is also a change in the fat content of milk. The milk fat rate during colostrum is very high, which is almost double that of conventional milk. Weeks 2-8, the lowest milk fat percentage. At the beginning of the third lactation month, the milk fat rate gradually increased again. Dry period. After the dairy cow finishes milk production during a lactation period, it needs to be dried milk to give the breast tissue a certain amount of rest time, and the cow needs to save necessary nutrients to prepare for the next lactation period. The dry period of cows is generally 50-60 days. The length of the cow should be determined according to the specific conditions of each cow. For cows over 5 years old, the dry period is 40-60 days. The nutritional conditions can be guaranteed and the impact on the milk production of the next baby is small. Estrus and pregnancy. During cows' estrus, there is a temporary reduction in milk production due to the effects of sex hormones. The decline is about 10%-12%. During this period, the milk fat percentage rose slightly. The effect of cow's pregnancy on milk production is obvious and continuous. In the early stages of pregnancy, the impact was minimal. Since the 5th month of pregnancy, since the placenta secreted estrogen and progesterone inhibited the lactation, the amount of lactation decreased significantly, and it declined rapidly in the 8th month, resulting in dry milk. Environmental factors feeding management. Dairy cows' feeding methods, feeding methods, milking techniques, milking times, etc. all have an impact on milk production. However, the supply of nutrients has the most significant effect on milk production. When milking conditions are good, milk production is also high. In the diet, a large amount of greenish succulent and silage was given, and various nutrients were properly matched, and full-price feeding was conducted according to the nutritional needs of lactating cows. Appropriate exercise, often brushing the body of cows, keeping ventilation in the barn, cleaning and drying, reasonably arranging workers' schedules, and regularly conducting preventive quarantine, etc., have a good effect on increasing milk production. Milking and breast massage. Correct milking and breast massage is one of the important factors to increase milk production. The milking technique is skilled and the milking frequency can be increased by appropriately increasing the number of milking. In general, milk can be used twice a day for milk cows under 15 kg milk. More than 15 kilograms of dairy cows, especially high-produced cows, should use 3 milkings. Squeezing the breasts and massaging the breasts with hot water before milking can increase milk production and milk fat percentage. Calving season. Under current conditions in our country, the most suitable calving season for cows is winter and spring. Because the cow's lactation after childbirth is just in the season where the green feed is rich and the climate is mild. During this period, the secretion of prolactin from cows was strong, and no mosquitoes and flies were attacked, which was beneficial to the increase of milk production. Outside temperature. The temperature range of Holstein-Friesian is 0°C-10°C, and the most suitable temperature is 10°-16°C. When the outside temperature rises to 40.5°C, the respiratory rate is accelerated 5 times, and the feeding stops. The milk production is significant. decline. Therefore, it is very important for dairy cows to do summer cooling work in summer. Relatively speaking, dairy cows are not afraid of heat and cold, and when the outside temperature is between 13°C and 20°C, the output of black-and-white cows begins to decline. As long as winter guarantees sufficient supply of silage and juicy materials, more protein feed will be provided. There will be no significant impact on milk production. disease. In the case of cows suffering from diseases and damage to health, their milk production is also reduced. In particular, diseases such as mastitis and nipples in the cow's lactation organs cause a more significant reduction in milk production.