Milk is rich in nutrients. Its ingredients can be divided into water and solids. Solids include milk protein, milk fat, lactose, minerals, vitamins and many other substances. The content of solids affects the quality of milk. The milk fat percentage is an important indicator to measure the quality of milk. The content is generally 3%-5%. Milk fat contains essential linolenic acid and peanut oleic acid and various fat-soluble vitamins and phospholipids. The main method to improve the milk fat percentage is to improve the dairy cow breed, choose high-quality feed, and raise the management is also one of the important factors to improve the milk fat percentage.
First, the selected breeds and individuals
The milk yield and milk fat percentage of different breeds of cattle are very different. The carefully selected varieties such as Holstein cattle have significantly higher milk production than local varieties. There is a negative correlation between milk production and milk fat percentage, and the milk fat yield of milk with higher milk yield is correspondingly lower. However, the varieties with high milk yield can be improved through planned breeding. Although different individuals in the same variety are in the same growth stage and under the same feeding and management conditions, their milk yield and milk fat percentage will still differ. For example, the milk production variation of Holstein cattle ranges from 3000 to 12000 kg, and the milk fat percentage ranges from 2.6% to 6.0%. Breeding excellent varieties and individuals and continuously improving them is an effective way to produce high quality and high quality cows.
Second, choose quality feed
The volatile fatty acid in the rumen metabolite of cattle is acetic acid. The proportional structure of propionic acid and butyric acid has a significant impact on the milk yield and milk fat percentage of dairy cows. After being absorbed, acetic acid is transported to the mammary gland for synthesis of a series of short-chain fatty acids in milk fat; propionic acid is absorbed and transported to the liver to become a raw material for synthesizing glucose; butyric acid is a kind of milk fat. Short-chain fatty acids can also be condensed with acetic acid coenzyme A to form higher fatty acids. The increase in the ratio of acetic acid and butyric acid is conducive to increasing the milk fat percentage of dairy cows. Milk fat is synthesized from two basic types of precursors. About 50% of the fat is synthesized from the mammary gland using acetic acid and acetic acid produced by rumen fermentation, and the rest is supplied by the fat of the feed or the fat accumulated in the body. The morphology of the chain fatty acids directly forms the different feed composition of the milk fat, which has a great influence on the in vivo synthesis of the swell.
1 crude fiber
The most important effect on milk fat in feed is the crude fiber content. The fiber is decomposed in the rumen to produce acetic acid, while starch can enhance rumen fermentation, lower the pH value, and promote the formation of propionic acid. The milk fat percentage is positively correlated with the ratio of acetic acid to propionic acid in the rumen. If the forage in the diet is less than 50%, or if the ADF (acid detergent fiber) is less than 19%, or if the crude fiber of the whole feed is limited to 13%, the reduction in dietary fiber content will result in an acetic acid/propionic acid ratio. Decreased, thereby lowering the milk fat content.
2 fat
The positive effect of fat is high energy and can provide fatty acids directly for milk fat synthesis. About 50% of milk fat must be supplied by fat in the diet. When the cow is in positive energy balance, it is difficult to use body fat and transport it to the breast. Therefore, dietary fat is the only source of milk fat during lactation. The negative effect of fat is the unsaturated fatty acid produced by unsaturated fat metabolism. In the rumen and hydrogen, it promotes the formation of propionic acid and reduces the milk fat content. Due to the addition of hydrogen, the formed monounsaturated fatty acid can also inhibit the fat in the mammary gland. synthesis. According to the above dual effects of fat, it is preferred to add 3% to 6% fat to the feed in order not to impede the characteristics such as rumen fermentation. Free oils often reduce the milk fat content, while whole oil seeds do not. Soybean oil or whole soybeans can reduce milk protein content, while cottonseed oil and cottonseed have little effect. Adding unsaturated fat or large doses of fat often leads to a decrease in milk fat percentage, mainly due to its effect on rumen fermentation. Therefore, people try to reduce the negative effects of fat by some measures, such as feeding whole or crushed oil cakes, treating with formaldehyde to prevent fat from fermenting, and using calcium saponification. These technical measures have different effects in maintaining and increasing the milk fat percentage. Gao Shizheng et al. (1998) reported that the addition of fatty acid calcium 300 g/day can significantly increase the milk fat percentage in milk compared with the control group (p<0.05), total linoleic acid and linolenic acid and calcium in essential fatty acids. Significant increase (p < 0.05). Cows add fatty acid calcium to cows with a milk fat percentage of 3.5% or less, which is not effective for cows with high milk fat percentage. Since 50% acetic acid must be used as a synthetic precursor due to the increase in milk fat percentage, when the fatty acid calcium is added, the diet is required to maintain the crude fiber level of 17% and ADF 21% (Zhang Yanli, 1996).
3 energy and protein
When the energy level of the diet is increased, the milk protein content is increased, but the milk fat percentage may be lowered. Increased protein content in the diet usually does not increase milk protein content, but protein may reduce milk protein when needed. Only when cows are under very low nutrition or chronic malnutrition can energy and protein have an effect on milk fat percentage.
4 inorganic salts
When the pH of the rumen is kept within the normal range, the formation of acetic acid is easier than that of propionic acid. Due to the increase of acetic acid, the feed intake, milk yield and milk fat percentage of the cows will be improved. The addition of an alkalizing agent to an easily fermented feed such as high-moisture cereals and silage corn can achieve satisfactory results, but the addition of an alkalizing agent to feeds containing more than 20% ADF such as hay and silage fresh grass has no significant effect. Most of the commonly used alkalizing agents are sodium hydrogencarbonate or sodium carbonate, and the mixture prepared by the ratio of magnesium oxide and sodium hydrogencarbonate in a ratio of 1:2 has a good alkalization effect. Zeolite can increase the pH of the rumen, but at the same time it may reduce the milk fat and milk protein content. Han Zhengkang (1986) reported that when the rumen is fermented in propionic acid, the addition of sodium acetate can increase the milk fat percentage.
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Third, scientific and standardized feeding management
1 Reasonable proportion of fine roughage
In dairy cow diets, the concentrate should not be over-emphasized, but should be based on high-quality roughage such as succulent green forage and green hay. After the supply of high-quality green hay and other roughage is sufficient, the insufficient energy is supplied by the concentrate, and the feed should be coarse and fine, and the concentrate should be fed as many times as possible to avoid ingesting a large amount of concentrate. Poewll (l939) first discovered that feeding cows with high-precision, low-calorie diets would result in a decrease in milk fat percentage. When the proportion of concentrate in the diet is higher, the proportion of acetic acid in the rumen decreases, and the proportion of propionic acid increases. Conversely, when the proportion of crude material is larger, the proportion of acetic acid increases. It can be seen that feeding the roughage is beneficial to increase the milk fat percentage. However, roughage does not provide raw materials for dairy cow's synthetic milk protein, which will affect milk production. Therefore, the cattle's diet should be reasonably matched, not only to provide the right amount of concentrate and juicy material, to ensure high yield of the cow, but also to ensure a certain proportion of roughage to increase the milk fat rate. In the production, the cows are fed with a method of mixing coarse or fine or coarse and coarse, and the proportion of crude materials is generally not less than 40% of the diet.
2 pay attention to the digestibility and physical form of the diet
It has been confirmed by a large number of dairy cow tests that the milk fat percentage is related to dietary fiber, and it is concluded that the effect of dietary fiber content and source on milk fat percentage may be directly related to the length of the fiber. Feeding cows should pay attention to the digestibility of the diet. The digestibility of high-yield dairy cows should not be lower than 65%. Both concentrate and coarse materials should pay attention to their digestive properties. Barley and sorghum are easily degraded in the concentrate, and the corn is relatively poor. The crude grass in the coarse material is easily degraded, and the other pastures are relatively poor. At the same time, we must pay attention to the physical form of the diet. The seed of the concentrate is broken or crushed, and the green feed is not too shredded. Generally, it is about 8 cm. The silage can be longer, so that the feed can be increased. The time in the digestive tract, thereby achieving the purpose of increasing the digestibility of crude fiber and dry matter, thereby increasing the milk fat percentage.
3 supplement fat
In general, the fat content of dairy cows is about 3%, and the relevant data show that cows have the highest nutrient utilization rate when the fat content in the diet is 5%-6%. Therefore, adding a certain amount of rapeseed or protective fatty acid to the diet can effectively increase the milk fat percentage, but the amount of addition should not be too high, and the fat content in the diet can be generally 5%-6%.
4 strengthen the management of dry period
The dry period of dairy cows is a stage in which the fetus needs more nutrients for rapid growth and development. Improving the nutritional status of the cows is also beneficial to the next lactation period, and the necessary conditions for prolonging the production period; while the secretion of mammary glands during dry milk is stopped, it is secreted. Epithelial cell renewal plays a necessary preparatory stage for normal secretion during lactation. Therefore, the cow's dry milk period provides sufficient nutrition and combined with scientific feeding management (such as strengthening the breast massage in the middle and late stages of dry milk), can effectively improve the milk fat rate.
5 master the correct milking method
Proper massage and milking operations enhance breast milk reflexes and increase milk production and milk fat percentage. Standardize and improve the milking technology. Every time you milk, try to squeeze the milk in the breast cells as much as possible. It not only increases milk production (10%-20% increase), but also increases the milk fat percentage by 0.2-0.4%. Master the milking speed and squeeze as much as possible within 5 minutes.
6 appropriate exercise
Cows are less likely to exercise, and if given proper exercise, they can not only exercise, strengthen metabolism, enhance health, but also increase milk production and milk fat percentage. Under normal circumstances, the cows should exercise freely for no less than 6 hours a day. According to reports, the cows drive 3 kilometers a day, can effectively increase the milk production and milk fat rate, but the exercise should not be intense, the time should not be too long, should be based on the physiological and nutritional status of the cattle. Excessive exercise can sometimes cause a negative balance of energy, causing ketosis.
Fourth, strengthen the prevention of dairy cow mastitis
Breast inflammation is an important factor affecting the milk yield and milk fat percentage of dairy cows, especially mastitis caused by Streptococcus lactis, Escherichia coli, Pasteurella, etc. The milk will be watery and the milk fat percentage will be significantly reduced. Because the cause of mastitis is complex and has many influencing factors, prevention work is difficult. To prevent mastitis, we must start from all aspects and take comprehensive measures to implement the principle of prevention and prevention. In daily management, we must do a good job in environmental and animal health, especially breast hygiene; pay attention to milking hygiene and correct milking; regular recessive mastitis or DHI measurement, for the detection of recessive mastitis is "++" Timely medication for the above reactions; pay attention to and adhere to the nipple medicated bath work, the immersion nipple liquid requires strong bactericidal power, low stress, stable performance, long acting time, commonly used 0.3%-0.5% chlorhexidine solution.
V. Feeding management measures for dairy cows in winter
Feeding cow's roughage in winter is far from meeting the physiological and maintenance needs of the cow, so a certain proportion of concentrate must be added appropriately. The main raw materials of concentrate supplements should be guaranteed in more than 3 kinds to maintain the comprehensiveness of nutrient sources. Generally, in the early stage of milk production, the ratio of refined to coarse materials is generally 3:7. With the peak of milk production, the cows are nutrition. The demand for the increase is increased, and the concentrate ratio can be appropriately increased. The ratio of fine to coarse can be adjusted according to the nutrient concentration level of the crude material. If the quality of the roughage is poor, the amount of concentrate can be increased appropriately, but it must not be too much, because eating too much concentrate will make some concentrates less than enough. Dairy cows are digested and fermented by microorganisms in the stomach, causing indigestion and even acidosis in dairy cows. Cows entering the winter, due to changes in the external environment, must lead to the consumption of physical energy of the cows. The main feed used to supplement its energy is corn, which increases corn by 20%-50% without changing the protein feed. The daily supply of high-yield dairy cows (more than 35 kg per day) should be 6-8 kg, and the amount of concentrate supplied to the general dairy cows should be no less than 3.2 kg per day. In the winter, cows should be fed more succulent feeds such as silage, micro-storage or beer grains to replace the grassy juicy green feed for dairy cows in summer and autumn.
Practice has shown that cows fed silage or micro-storage in winter have nearly twice as much milk as cows that are not fed silage or micro-storage. It can be seen that if the cows are fed enough succulent feed in winter, the milk yield can be increased. It is necessary to take measures to keep warm and keep out the cold. The optimum temperature in the barn is 16-20oC. If the cow is in a low temperature for a long time, the cow loses a lot of heat, and the resistance is reduced, which is easy to get sick. Therefore, in the winter, it is necessary to block the loophole around the wall of the cow house early to prevent the wind from invading. The doors and windows in the barn should be filled with glass or paste paper, and the curtains and curtains of grass or cloth should be hung to prevent the wind from entering the church. Thick circles of grass in the circle, no conditions to lay dry soil, to prevent freezing the breasts. It is necessary to achieve "three warmths" in cattle houses, feed and drinking water. The temperature of adult cattle should be kept above 6oC, and the temperature of the breeding house should be kept above 5oC. Do not feed with frosty, moldy feed.
Many breeders only drive cattle into the house during the winter, and usually put the cows in the yard. As the temperature drops, the cows lose energy and seriously affect the milk production. After entering the winter, when the temperature drops to minus 15oC, the cows should be driven into the enclosure for the night to prevent frostbite or excessive consumption of body energy, thus affecting the milk production. In winter, the temperature in the barn is generally kept at 10-25oC, and the temperature is too high, which will have a negative effect on cattle. Due to the single composition of the forage in winter cows, 5-15 grams of calcium and phosphorus must be added to the feed daily. In order to prevent salt poisoning in dairy cows or other adverse diseases caused by excessive salt, try not to add the proportions to the feed when adding salt to the cows. It is advisable for the cows to eat freely. Try to purchase salt bricks and salt tanks.
1 increase lighting
Cows are raised in winter, and artificial light is used to simulate the summer natural environment, which can greatly increase the secretion of prolactin and increase the milk production. American researchers use white fluorescent lighting to cycle white and night at a ratio of 16 hours and 8 hours, increasing light, and milk production can be increased within 2-6 weeks of exposure. In the spring, autumn and winter seasons, the daily milk yield per cow can be increased by 10%.
2 for warm water
In winter, cows eat more hay. If they do not drink enough water, the appetite of the cows will drop. Cows need 5 kg of water for every kilogram of dry feed. Therefore, the number of cows drinking in winter cannot be lower than in summer. It is required to drink water once every morning, afternoon and evening. The drinking water temperature should be close to the body temperature of the cow (38-40oC), and it is strictly forbidden for the cow to drink the ice water.
3 insist on appropriate exercise outside the house
From the grazing to the cows after feeding, the amount of exercise is greatly reduced, especially after feeding the full-price diet, the cows are not enough to eat, and it is easy to over-fertilize. This is unfavorable for the cow's constitution and milk production, and it is easy to incur ketone. Urine and so on. The pastoral area can be combined with grazing. When the agricultural area is warm at noon, the cattle can be driven into the playground for free activities, or they can be driven for one hour. It can not only enhance the disease resistance of cattle, but also strengthen the ability of cattle to keep out the cold. But pay attention to safety, prevent slipping, but also prevent colds, do not freeze the cattle, in order to prevent the nipples from freezing, you can make cotton bras, with ropes around the cow body fixed a week, have a good warmth. Brush the cow often. In the cold winter, the blood vessels of the bovine epidermis contract. Regular brushing of the bovine body can promote blood circulation and has a significant effect on increasing the milk yield of the cow.
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