1. Genetic factors
Variety differences.
Different breeds of dairy cows have great differences in milk yield and milk fat rate. Compared with local breeds, the milk yield of highly cultivated breeds is significantly higher. Besides, there is an inverse relationship between milk yield and milk fat rate, that is, milk yield of dairy cows is higher and milk fat rate is relatively lower, but through planned breeding, milk fat rate can also be improved. Nowadays, among the five major dairy breeds in the world, black and white cows have the highest milk yield.
Individual differences.
Within the same breed, for different dairy cows, there are still differences in milk yield and milk fat rate, although the physiological stages and the feeding and management conditions are the same. For example, the milk yield of black and white dairy cows can vary in the range of 3000-12000 kg, and the milk fat rate can vary in the range of 2.6-6.0%.
Physical and weight differences.
For dairy cows with different body size and weight, their milk production is different. Normally, the larger the cow's physique, the larger its body and digestive tract capacity, the more it needs to eat, coupled with its larger lactating organs, resulting in a relatively larger milk yield than small cows. Within a certain range, dairy cows can lactate 1000kg per 100 kg body weight, but beyond a certain range, although the weight of dairy cows is increasing continuously, the milk yield will not increase significantly, so the weight of dairy cows in the range of 550-650 kg is more appropriate.
2. Feeding management level
Milk production performance of dairy cows is closely related to the level of feeding and management. Under good feeding and management conditions, dairy cows can not only increase their milk production directly but also advance their production age by accelerating their growth and development. At the same time, they can improve their reproductive performance and ensure the continuous and healthy development of cows, to improve the production level of the whole cattle farm. Poor feeding and management conditions can easily lead to lower reproductive capacity and milk production, delay delivery of months, and ultimately lead to a significant decline in the production level of dairy cows. Therefore, it is necessary to make dairy cows have good feeding and management conditions.
The energy, protein, minerals and vitamins needed for the growth and development of dairy cows and their production can only be absorbed from the feed. Therefore, the corresponding feed should be fed according to the feeding stage, so as to ensure the increase of milk production and promote the growth and development of dairy cows. The feed of dairy cows should be diversified, based on high quality hay and green feed. The undernourished part should be supplemented by adding concentrate and appropriate additives. According to the calculation of dry matter, it is advisable to control the proportion of roughage, green feed and concentrate in the diet of dairy cows at 3:5:2. Especially in the lactation period of dairy cows, it is necessary to mix different kinds of feed to ensure that there are more than two kinds of green juicy feed and roughage, such as hay, straw or corn husk. The concentrated feed consists of more than four kinds of raw materials, such as corn flour, barley, cake, bran and so on. If conditions permit, dairy cows can also feed some by-products such as brewer's grains, tofu residue, and peel.
In terms of management, to ensure that dairy cows keep a proper amount of exercise every day during the feeding period, which can not only exercise, promote health, and strengthen physical fitness, but also improve lactation performance. Dairy cows can keep high yield and good health if there are good drinking water conditions. It's better to install automatic water dispensers in the cowshed and water tanks in the playground so that cows can drink clean and freshwater anytime and anywhere. The drinking water temperature of dairy cows is usually controlled at about 10-15 ℃, especially in winter, we should pay more attention to providing warm water to cows, to keep milk production relatively stable and improve, and help to maintain body temperature, promote appetite increase, and enhance blood circulation. If the cow drinks cold water in winter, a large amount of heat energy in the body is consumed to increase internal, thus significantly reducing their milk production.
3. Environmental temperature
Generally speaking, dairy cows are cold-resistance and not heat-resistance. The suitable temperature range is 0-20℃, of which 10-16℃is the most suitable temperature. It is reported that when the ambient temperature drops to - 13 ℃ or rises to about 25℃, the milk production of dairy cows will begin to decrease significantly. This is because the temperature is too low, the body increases heat dissipation, resulting in increased energy loss, making it difficult to maintain normal physiological function, which leads to a decline in milk production. High temperature leads to a lower feed intake of dairy cows, which causes lower milk production.
Therefore, in the daily management of dairy cows, it is necessary to strengthen cold prevention and warm protection in winter and heat prevention and cooling in summer, to avoid the phenomenon of seasonal milk production. To prevent cold and keep warm in winter, loopholes must be blocked and doors and windows repaired before entering winter to keep the cowshed well insulated. Water is forbidden to wash the cowbed to ensure its dryness. Feed cows with warm feed and warm water and feces are cleared in time, while the amount of feed can be increased appropriately.
4. Disease and stress factors
Milk production of dairy cows is also affected by certain diseases, mainly mastitis, metabolic diseases, hoof diseases, obstetric diseases, consumptive diseases, digestive system diseases and other infectious diseases and common diseases that can lead to elevated body temperature. Among them, mastitis is a common disease in dairy cows, and it is harmful to their production. It is reported that the incidence of clinical mastitis in dairy cows is about 3%-5%, accounting for 20%-25% of the total incidence, and the incidence of recessive mastitis is about 38%-62%. The number of cows eliminated due to mastitis is about 10%-15% of that of adult cows. Therefore, prevention and treatment of cow diseases must be strengthened to minimize the impact of diseases on cow health and milk production. Stress factors, such as drastic changes in weather, long-distance transportation, sudden change of feedstuffs, exposure to severe noise stimulation such as firecrackers and electric saws, may lead to reduced milk production in dairy cows.