What nutrition do cows need?

Water is an essential nutrient for animals, accounting for 60% ~ 70% of their weight. If animals are seriously short of water or lose 20% water, it may be life-threatening. The distribution ratio of water in the body is 65% ~ 75% in intracellular fluid, 20% in interstitial fluid and 5% in plasma. Therefore, it has a very important role and position in dairy cows.

Studies have proved that under normal circumstances, dry cows need to drink 35 liters of water every day; Dairy cows with daily milk production of 15 kg need to drink 50 liters of water every day; High-yield dairy cows with a daily milk production of about 40 kg need to drink about 100 liter of water every day. In hot season, cows need more water than in spring, autumn and winter.

② protein.

All life and production activities of animals must involve protein. Protein's nutritional function in animals can't be replaced or transformed by any other substance. When the supply in protein is insufficient, the growth and development of young animals are slow and emaciated, the semen quality of breeding animals is reduced, the sexual cycle of female animals is abnormal, the fetus is stunted, and even weak fetuses and stillbirths are produced, and the newborn weight of young animals is small. Too much protein in the diet has a bad effect on animals, which not only causes waste, but also leads to metabolic disorders and even diseases.

(3) Energy

Because the efficiency of converting metabolic energy into maintenance and net milk production is very similar, the same index is used for the convenience of application. Therefore, the milk yield, maintenance and growth of China dairy cows in feeding standard are expressed by net milk production energy. Cow feeding standard adopts the standard milk energy equivalent to 65,438+0 kg and 4% fat content, that is, the net milk production energy of 3.65,438+0.38 MJ is taken as the energy unit (NND) of cows. The energy demand of dairy cows can be divided into maintenance demand (including extra demand when temperature changes), milk production demand, weight gain demand and late pregnancy demand.

④ crude fiber

Cows are ruminants. In order to maintain normal digestive function, the supply of crude fiber must be considered in diet. Crude fiber mainly includes cellulose, hemicellulose and lignin. They are of great significance to dairy farming:

① Maintain normal rumen fermentation and digestive physiology of cattle.

When cows get enough neutral detergent fiber from the diet, they can ruminate for 7-8 hours every day, so they get1160 liters of saliva to enter the rumen, and then the volatile fatty acids produced by fermentation in the rumen are buffered to keep their hydrogen ion concentration at 100 ~ 1000.

When the average length of cellulose is above 0.64 cm, it will play the above role.

② Maintain normal milk fat rate.

When the crude fiber in dairy cows' diet is lower than 17%, or the effective neutral detergent fiber is lower than 2 1%, the milk fat rate will decrease obviously. When the rumen fermentation of dairy cows is too fast, that is, the fermentation is unbalanced, the milk fat rate will also decrease, and the direct reason is that the digestibility of neutral detergent fiber in rumen decreases.

The processing length of roughage for high-yield dairy cows should be 1 ~ 4cm, accounting for 40% ~ 50% of the total amount of neutral washing fiber, in order to maintain the normal physiological function of rumen, maintain its normal milk production level and milk fat rate.

③ Prevent gastric acidosis and keep limbs healthy.

When the effective neutral detergent fiber in dairy cows' diet is insufficient, the rumen fermentation type will change from acetic acid fermentation to propionic acid fermentation, and the rumen acidity will increase (pH 5 ~ 5.5), which will lead to rumen poisoning and limb and hoof diseases such as keratinization of rumen nipple (mucosa) and hoof inflammation.

④ Prevent gastric displacement.

When the roughage in dry dairy cows' diet is too short (less than 1 cm) and the concentrate-feed ratio is more than 50%, four gastric displacements can occur. Therefore, dry cows should be fed with 3 ~ 4 kg of coarse forage of Gramineae with a length of 3 ~ 4 cm to prevent gastric displacement.

⑤ Mineral elements

① Calcium

99% of calcium exists in bones and teeth. Calcium can regulate the excitability of muscles and nerves. When the calcium concentration is high, the excitability decreases. Calcium also plays an important role in blood coagulation. In the early stage of lactation, the sudden increase in the demand for calcium in milk production will lead to the decrease of blood calcium, which will lead to puerperal fever. If not treated in time, it will lead to the slow heartbeat of dairy cows, making them unable to stand, walk or even die in a coma. Calcium deficiency in calves causes rickets, while calcium deficiency in adult cows easily causes chondrosis and osteoporosis. Roughage, mainly leguminous crops, can generally meet the calcium demand for maintaining growth and limiting milk production.

② Phosphorus

80% of phosphorus in human body exists in bones and teeth. Because phosphorus has many functions, such as participating in energy metabolism, being a part of genetic material and participating in body fat transport, there is no specific symptom of phosphorus deficiency. In fact, because phosphorus is closely related to calcium, phosphorus deficiency is very similar to calcium deficiency. In addition, nonspecific symptoms are decreased appetite, disease resistance and reproductive rate. When feeding a large amount of grain or plant protein feed, or low-quality roughage, it is necessary to supplement phosphorus to meet the needs.

③ Salt

According to the severity of salt deficiency in dairy cows, the symptoms of salt deficiency are as follows: (1) lick or bite various items to obtain sodium salt; No appetite; Not strong, gaunt, dull eyes, rough fur, etc. ; Decreased milk production or slow weight gain; Tremor, dyskinesia, weakness and irregular heartbeat can lead to death in severe cases. Dairy cows have a strong ability to store sodium, and only long-term deficiency will show symptoms.

A. Salt requirement of lactating cows

According to 0.46% of net dry matter content in diet or 1% of compound feed (or concentrate supplement), it can meet the needs of dairy cows. Generally, lactating cows are fed 15g salt every day; If the daily milk production exceeds 20 kg, you should feed 30 grams of salt.

B. salt requirements of non-lactating dairy cows

According to the daily dry matter intake of 0.25% ~ 0.3%, it can meet the needs.

The amount of salt can be slightly higher in summer, but it should not be increased in winter, because eating more salt will increase the amount of drinking water. When the water temperature is low in winter, drinking more cold water will reduce rumen function, and raising the temperature of cold water to body temperature will greatly increase energy consumption. For example, raising the temperature of 1 kg water from 10℃ to body temperature (38.5℃) will consume 0.1/9 mj of energy.

④ Potassium

The minimum requirement of potassium for lactating cows is 0.9% of dry matter in diet. High-yield dairy cows (30 ~ 60 kg) are 65,438+0%. During heat stress, the requirement of potassium increased, which was about 65,438+0.2% of the dry matter of diet. The potassium content in dairy cows is 0. 15%, and potassium is lost from milk and sweat, so it should be supplemented in a balanced way every day throughout the summer to be effective. The requirement of potassium for bulls and growing cows is 0.65% of the dry matter of diet.

⑤ Magnesium

The content of magnesium in milk is about 0.0 15%, and the demand for magnesium increases with the increase of milk output. Magnesium deficiency can cause convulsion, magnesium and phosphorus deficiency in cattle, and also make milk alcohol positive and milk diluted. The maintenance requirement of magnesium for dairy cows is 2 ~ 2.58g/(sun), and 0. 1 2g is added for every1kg of milk.

The dry matter content of diet is about 0.2%. High-yield dairy cows with daily milk output of more than 35 kg in early lactation need 0.25% ~ 0.3% magnesium, and 0.5% ~ 0.8% magnesium chloride can be added to the diet to meet the needs, usually added to concentrate. The requirement of magnesium per kg body weight of calves is 12 ~ 16 mg, which is 0.07% ~ 0. 1% based on dry matter of diet. 0. 16% is suitable for dry cows, bulls and growing cows.

⑥ Sulfur

Sulfur is needed for microbial synthesis of bacterial protein and B vitamins in rumen of dairy cows. Rumen bacteria can use inorganic sulfur (sodium sulfate) to synthesize sulfur-containing amino acids (methionine and cystine), and then synthesize bacterial proteins. Milk contains 0.03% sulfur, most of which exists in the form of methionine and cystine. The sulfur requirements of lactating cows are about 0.2% of daily dry matter, 0.25% in early lactation, 0.29% in calves, and 0. 16% in dry cows, bulls and other growing cows. Adding sodium sulfate, calcium sulfate, potassium sulfate and magnesium sulfate to the diet of high-yield dairy cows can maintain its optimal sulfur balance. The suitable nitrogen-sulfur ratio for maintaining the maximum feed intake of lactating cows is 10 ~ 12 ∶ 1. Sulfur deficiency in dairy cows' diet will reduce feed intake and digestibility, slow down weight gain and reduce milk production. Excessive sulfur level will also reduce food intake, cause excessive burden on urinary system, and interfere with the metabolism of selenium and copper.

[6] Trace mineral elements

Cows need a small amount of trace elements, but they are necessary for their physiological functions. Trace elements are usually expressed in mg/kg. The content in cow or milk can also be expressed in this way. Trace elements include: iron, copper, cobalt, manganese, zinc, selenium, molybdenum, chromium and silicon. 10 elements, especially the first 8 elements are more important for dairy cows.

vitamin

Vitamins are essential nutrients for dairy cows to maintain normal production performance and health. There is sufficient evidence to prove that rumen microorganisms synthesize B vitamins and vitamin K. Therefore, traditionally, there are only three vitamins that need to be provided for cattle from feed: vitamin A, vitamin D and vitamin E. However, recent research shows that with the increase of milk yield of dairy cows, the increase of concentrate ratio in diet and the destruction of vitamins in feed processing, some water-soluble vitamins are added to the diet. Such as thiamine (vitamin B 1), nicotinic acid (calcium pantothenate) and vitamin C, can improve the production performance of dairy cows, improve milk quality, enhance immune function and reproductive function, and reduce the occurrence of diseases.

Cows need to get vitamin A and vitamin E from their diet. Under ultraviolet irradiation, 7- dehydrocholesterol under the skin of dairy cows can synthesize vitamin D, but vitamin D should be added to the diet of closed-house dairy cows and high-yield dairy cows. Rumen microorganisms can synthesize enough vitamin K. At the same time, high-yield dairy cows fed with a lot of silage but lacking sunlight, especially dairy cows that use straw as roughage for a long time, need to add vitamin D, vitamin A and vitamin E to their diets to maintain their health and production performance.