Adult cows have a strong productive capacity and must be scientifically reared to fully exploit their potential for lactation. Cows that are in lactation or gestation stage, if not properly managed, will affect its milk production, normal reproductive function and health. Knowing the nutritional and physiological characteristics of dairy cows will help us to fully understand some of the special features of dairy cows' feeding and management, so as to better cultivate dairy cows.
Cow's nutrition distribution and utilization
In the process of digestion and utilization of nutrients by dairy cows, fecal energy is the main form of energy loss, which is approximately 30% to 32% of the total energy consumed. Part of the energy is converted into digestive energy (DE), urine energy, and methane. Energy can increase body heat by about 30% of total energy. Only 40% of net energy can be used for production. About one-third of the net energy is used for maintenance needs, and the rest is used for production.
From the use of the order of view, the need for maintenance is the first, followed by reproduction. The milk production performance of the first cow was also used for reproduction. After long-term research, people had a very high production capacity. For mature cows, their own weight gain is at the last position of the nutrient distribution. Therefore, when nutrition can not meet the demand, it will use its own body tissue components in order to produce milk. The use of its own body composition is mainly in the pre-milk period (0 days to 70 days postpartum), so in this period should try to meet the nutritional needs of cattle, to prevent it from losing too much weight, especially for high-yield dairy cows.
The high production capacity of dairy cows during the lactation phase and their need for nutrients
Dairy cows are ruminants with high production capacity. A cow with a weight of 600 kg and an annual output of 6,000 kg of milk will be converted to dry matter (11% to 14% of dry matter in milk). This does not include 1 yak produced. Only milk is produced. One animal product it provides exceeds its own weight. Such high production capacity is incomparable to other livestock. According to reports, for every kilogram of milk produced by a dairy cow, 500 kilograms of blood are required to return from the heart to the breast and then back to the heart. At the same time, there are also large amounts of nutrients for milk production. Therefore it must be provided with sufficient nutrients, otherwise it is difficult to maintain high production performance.
Effect of Proportion of Ingredients in Raw Grains of Dairy Cattle on Health and Production of Dairy Cows
Many studies and productions have actually proved that high concentrates are detrimental to dairy cows, and the proportion of refined coarse material should be ensured in the diet. The supply of hay silage should account for at least 1/30 of the dry matter quality, and feed dry matter should contain at least 15% crude fiber. High concentrates will cause large proliferation of lactic acid bacteria, increase ruminal acidity, inhibit or kill other rumen microorganisms, cause rumen metabolic disorders, lead to loss of appetite, rumen swelling and other discomfort, while reducing the proportion of acetic acid, milk fat rate decreased. The rough material used should be of good quality. If straw feed is best treated by ammoniating, it is best to feed with some high quality coarse material, otherwise it is difficult to meet the nutritional needs of dairy cows. At the present stage, some individual cattle-raising households often use straw as their main raw material in the absence of high-quality coarse material in winter, and they rarely deal with it, which to a certain extent limits the exertion of lactating potential of dairy cows. In the future, we should further focus on the production of high-quality raw materials, and at the same time, strengthen the popularization and application of methods such as straw ammoniating. If corn silage is used in combination with hay, the dry matter ratio of the two is better than 2:1, and silage raw corn is suitable for a length of 1.0 cm to 1.5 cm.
Cow nutritional requirements and nutritional needs during lactation
The digestible total nutrients in the feed during the lactation period are high and should contain enough crude fiber. The feedstuff preferably includes cotton seeds, soybeans, and other fatty or animal fats having high fat content. During this period, crude protein should account for 16%~18%, calcium 0.7%, phosphorus 0.45%, and the crude/crude ratio should be controlled at 40~46:50~54 as much as possible. In order to avoid a drop in butterfat ratio, crude fiber should not be less than 17% (accounting for dry matter in the diet). The milk cow feed consisting of 600 kg of body weight and 40 kg of milk per day consists of 12 kg of concentrate, 25 kg of silage, 4 kg of hay and 5 kg of juicy feed.
It has been determined that high-yielding dairy cows eat enough feed, and they have to eat at least 8 hours per day. Currently, in the case of milking three times a day, the intake time of dairy cows is generally not enough, and the milking period of dairy cows should extend the feeding time and increase the number of feedings.
During the mid-lactating period, the milk production of cows began to decline gradually, and the decrease ranged from 6% to 8%. At the same time, after the pregnancy of the cow, the nutritional needs of the cow have been reduced. This feature should be seized so that it can eat more hay and supplement the concentrate properly so that the milk production and fat percentage can be maintained at a relatively high level. The lactose ratio of the mid lactation diet can be controlled at 40-45:55-60.
During the late lactation period, the milk production of cows has dropped significantly, and it is easier to raise at this time. This stage should be used to intensify the recovery of dairy cows. There is still potential for milk production during this period, so cows cannot be overgrown.
Milk Cows' Milk Production During Lactation
Cows started lactation under the action of thyroxine, prolactin, and somatotropin until the dry period (about 305 days). Daily milk production changes during the milk production period have a certain pattern.
Generally, postpartum milk production gradually increases, reaches the peak of lactation at 6 weeks to 8 weeks, and starts to decline after maintaining for a certain period of time. About 200 days after birth, due to the influence of pregnancy, milk production further declined until dry milk or lactation stopped.
The average milk production of cattle is not a smooth curve for each individual cow. Individual cows are affected by many factors during the lactation period, and their milk production changes will be curved.
From the lactation curve, it can be seen that the highest daily (or monthly) milk production, and the lower part of the curve, the area between the horizontal and vertical coordinates is the total milk production during the lactation period. There are two main factors that determine the shape of the lactation curve, namely the highest daily milk yield and lactation persistence.
The recovery of appetite during the postpartum lactation period of dairy cows In the later stages of pregnancy, the fetus gains weight rapidly, and the fetus presses the gastrointestinal tract in the uterus, causing postpartum loss of appetite. Generally, cows reach the peak of dry matter intake from 10 weeks to 12 weeks postpartum, and gradually decline with the course of pregnancy. In this way, the peak intake of dry matter intake is about one month later than the peak milk production period. Cows will experience a negative balance of nutrients at the beginning of lactation, which will reduce body weight and affect the body condition and breeding of dairy cows. Especially for high-yielding dairy cows, this contradiction is even greater and the impact is also great. Its large intake, more than fattening cattle, only to ensure adequate dry matter intake to obtain high milk production, especially in the pre-lactating period, should try to increase its intake and feed nutrient concentration.
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