Increasing Utilization of Urea in Ruminant Feeding

The nitrogen content of urea is 42-46%. If 70% of the nitrogen in urea is calculated from the synthetic bacterial protein, 1 kilogram of urea can be converted into protein equivalent to 4.5 kilograms of soybean cake after ruminal transformation of ruminants. According to foreign reports, adding 1 kilogram of urea to a protein-deficient diet can produce 6-12 kilograms of milk or 1-3 kilograms of more weight, and can also produce 50-150 grams of net hair. Domestically, 3.6-4.6 kilograms of milk per kilogram of urea have been obtained.

Rumen bacteria in ruminants use urea as a nitrogen source and soluble carbohydrates as a source of carbon and energy to synthesize bacterial proteins. Then, like the feed protein, under the action of animal digestive enzymes, passive objects digest and absorb.

However, ammonia decomposition of urea is not all in the rumen bacteria protein synthesis, and the use of urea is also affected by a variety of factors, in order to improve the utilization of urea and prevent ruminant ammonia poisoning, feeding urea should pay attention to the following several aspects:

1. There must be a certain amount of easily digestible carbohydrates in the diet supplemented with urea. In the process of using ammonia to synthesize bacterial proteins, rumen bacteria need to supply available energy and carbon racks at the same time, and carbon racks are mainly supplied by carbohydrate glycolysis. Experiments have shown that when crude fiber alone is used as energy source in cattle and sheep diets, the utilization rate of urea is only 22%, and when adequate amounts of crude fiber and starch are supplied, the utilization of urea can be increased to more than 60%. This is because The rate of degradation of starch is similar to that of urea, and the release of energy and nitrogen sources tends to be synchronized, which is beneficial to the synthesis of bacterial proteins. Therefore, when urea is added to the diet based on roughage, the starch concentrate should be properly added, and every 100 grams of urea should be added. It can be used with 1 kilogram of easily digestible carbohydrates, including 2/3 of starch and 1/3 of soluble sugar.

Second, supplement the urea diet in the protein level should be appropriate. When the protein content of the ruminant diet exceeds 13%, the rate and utilization of urea in the rumen to transform into bacterial proteins are significantly reduced, and ammonia poisoning may occur. When the protein level in the diet is lower than 8%, it will affect the growth and reproduction of bacteria. It is generally believed that the protein level in the diet should be between 8-13% before the ruminant supplements urea.

Third, ensure the supply of minerals necessary for microbial life activities. Cobalt is a vitamin B12 component that plays an important role in protein metabolism. If there is a deficiency of cobalt in the diet, the synthesis of vitamin B12 is hindered, which will affect the use of urea by bacteria. Sulfur is a raw material for the synthesis of methionine, cystine and other sulfur-containing amino acids in bacterial proteins. While ensuring sulphur supply, attention should also be paid to the ratio of ammonia to sulphur and nitrogen to phosphorus. The optimum ratio of nitrogen to sulphur for urea-containing diets is 10-14:1, and the optimal ratio of nitrogen to phosphorus is 8:1. In addition, the supply of calcium, phosphorus, magnesium, iron, copper, zinc, manganese, and iodine, which are necessary for the life activities of bacteria, must also be guaranteed, which is conducive to improving the utilization of urea.

Fourth, control the amount of feed. The amount of urea fed is about 20-30% of the crude protein content of the diet, or no more than 1% of the dry matter of the diet. Adult cattle are fed 60-100 grams per day, and adult sheep are fed 6-12 grams per day. Yak and lambs within 2-3 months after birth are forbidden to feed urea because their rumen function is not fully developed. If the diet contains non-protein nitrogen high feeds such as silage, the amount of urea should be halved. If it exceeds this amount, it will cause waste. Second, ammonia poisoning will occur in ruminants. Poisoning usually occurs within 0.5 to 1 hour after feeding. Symptoms of poisoning include exercise disorders, muscle tremors, cramps, and shortness of breath. Mouth foamed. If not treated, it may die within 2-3 hours.

Fifth, pay attention to feeding method. In order to use urea effectively and prevent urea from ammonia poisoning in ruminant feeding, when feeding urea, it is necessary to feed urea evenly into roughage, and it is better to use urea to dilute the urea or use concentrate to mix urea. After mixing with coarse material, urea can also be added to the silage material and then fed together with silage. The practice is to uniformly add 4 kg of urea and 2 kg of ammonium sulfate to 1 ton of corn silage material. When fed with urea, there are a few to many, so that ruminants have 5-7 days of adaptation. The amount of urea fed a day is divided into several feedings. Raw urea and barnyardgrass and other feeds containing urease are not fed in large quantities and mixed in urea-added cereal feeds. It is strictly forbidden to feed urea alone or in water, and should drink water after urea is fed for 3-4 hours.

Six, using high-efficiency urea additives. In order to reduce the decomposition rate of urea in the rumen, the bacteria have enough time to use ammonia to synthesize the bacterial protein, improve the utilization rate of urea and feed safety. The following measures can be taken when feeding urea: (1) Adding to urea diet Urease inhibitors, such as oxalic acid, fatty acid salts, sodium tetraborate, etc., inhibit urease activity. (2) Coated with urea. Use cooked corn batter or sorghum batter with urea and feed. According to experiments, only 50% of the coated urea granules in warm water at 35°C were dissolved after 2 hours, and all were dissolved without coating urea for 9 minutes. (3) The method of making granules of granule gelled starch is as follows: the crushed grains (70-75%), urea (20-25%), bentonite (3-5%) are mixed, and subjected to high temperature and high pressure blasting to make The starch gels and binds tightly to the thawed urea. This product reduces the rate of ammonia release while accelerating the rate of starch fermentation, maintaining the simultaneous release of nitrogen and improving the efficiency of bacterial protein synthesis. (4) Urea block. The urea, honey, minerals, etc. are pressed into natural solidified masses to allow the cattle and sheep to feed. This controls the ingestion speed of urea, thereby increasing the utilization of urea. (5) Feed urea derivatives such as urea phosphate, biuret, fatty acid urea and the like. Compared with urea, its degradation rate is slower, and its feeding effect and safety are high.

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