All along, I thought urea was just a simple fertilizer, but I went to an uncle's cattle farm some time ago to know that urea can still be given to cattle. But it is worth mentioning that urea can only be added in a small amount. Once overdosed, it will lead to illness and even death of cattle. What's going on here? Let's talk about this problem together.
Urea for cattle?
0 1 the source of urea
Urea is an organic compound composed of carbon, nitrogen, oxygen and hydrogen. It has existed since the appearance of animals, because urea is actually protein, and ammonia will be produced in the process of catabolism in animals. The toxicity of pure ammonia will damage the animal body, so animals must find ways to turn it into a non-toxic substance and then metabolize it.
At this time, the ability of animal liver is reflected. Ammonia will react with carbon dioxide, water and aspartic acid in the liver to produce urea, which is called urea cycle.
After urea is formed, a small amount will enter the blood and then be excreted from our sweat, but most of it will pass through our kidneys and then be excreted through urine. Because urea is a kind of white crystal that is easily soluble in water, the white salt that appears after our clothes are soaked in summer is actually because of urea, and something similar to hoarfrost will be formed on the ground where we often urinate, which is actually urea.
Although urea has always been accompanied by the metabolic system of animals (mammals and amphibians), it was discovered by the French scientist Hilaire-Marin Rouelle in 1773 and then applied to agricultural cultivation.
After the discovery of urea, people always thought that animal metabolism was the only way to produce urea, but this cognition was broken by German chemist Friedrich W?hler 55 years after the discovery of urea, namely 1828. However, this break was unintentional, because at that time, Willer wanted to get a new compound by reacting ammonium cyanate with ammonium sulfate, but unexpectedly got urea.
This discovery not only obtained urea, but also broke the long-recognized vitality theory and opened up organic chemistry. But now urea is more simplified in industry, and chemical urea can be obtained only by ammonia and carbon dioxide under certain conditions.
02 urea for cattle?
Since urea was discovered, people have been exploring its uses. During the period of 1879, foreign scientists found that ruminants have the ability to convert non-protein nitrogen into protein, but they didn't know the specific mechanism at that time.
In 1949, a scientist made further research on the basis of this idea. He mixed the urea capsules marked with N 15 into the Leymus chinensis feed for the sheep to eat. It was found that protein labeled N 15 was detected in sheep viscera and blood four days later.
With this discovery, in the same year, another research group directly fed a certain amount of urea to sheep, and found that sheep was actually in positive nitrogen balance (nitrogen intake exceeded excretion), which means that sheep did something with urea. Through further research, the research team found that microorganisms in sheep rumen can actually use urea to synthesize the protein they need, so that microorganisms can grow and reproduce with energy. In addition, microorganisms in sheep rumen actually need nitrogen to synthesize protein, while urea contains nitrogen.
At this point, the problem is solved. Cattle and sheep are ruminants. Their food first enters the rumen, and the trace protein in forage is decomposed into amino acids needed by cattle and urea needed by themselves by a large number of microorganisms in rumen.
Feeding cows with proper amount of urea artificially can make the microorganisms in rumen more active and make ruminants such as cattle and sheep digest and absorb food better. In this way, obviously cattle and sheep will grow better, and the biggest "killer" stomach disease of ruminants will rarely get sick. This is why urea can be fed to cattle. Not only cattle and sheep, but also other ruminants.
However, although urea is beneficial to cattle, it is extremely counterproductive. As an organic compound, urea is also a double-edged sword. According to scientific research, the semi-lethal dose (LD50) of urea to cattle is 0.45g/kg, which means that once it exceeds 225g, even cattle weighing 500kg will die, which is called "urea poisoning".
This is because once the urea is excessive, microorganisms can't use it, urease in rumen will decompose the excessive urea into carbon dioxide and ammonia, which will lead to cow poisoning.
Why don't bison need urea supplement?
All domestic animals have a wild ancestor, for example, the ancestor of domestic pigs is wild boar, the ancestor of dogs is wolf, and the ancestor of chickens is primitive chicken, and so on. The same is true of cattle. Take yellow cattle as an example. Their ancestor is B.primigenius, a bison that once spread all over Eurasia. They were domesticated 8,000 years ago.
Obviously, people haven't found urea, and wild ruminants don't drink urine, so why don't cows need to supplement urea? The answer lies in the state of being.
The first is exercise. In the wild environment, the foraging time in Niu Yi can reach 10 hour. During this period, they eat and walk, and this amount of exercise will be full at the end of the day. Moreover, in Eurasia, the biggest natural enemy of cattle is wolves, and the pursuit of wolves is also crucial to their physical consumption. Therefore, it is not easy to have problems because of more exercise and good digestion.
However, if domestic cattle are herded every day, this kind of semi-free farming does not need urea, but the narrow space of the farm makes them have little opportunity to move, so their digestion ability is poor.
Followed by food. In the wild environment, the original cattle eat forage, which is all natural. Although the heat is low, the large quantity makes up for the lack of energy, so the original cow is not prone to problems. However, under the condition of human feeding, the food of cattle is synthetic feed. Although these feeds are scientifically matched, in the case of low activity and high food safety, cows in farms are prone to digestive problems, and most of the digestive problems are concentrated in rumen, that is, eating more and digesting less, so urea is needed at this time.
abstract
Urea is a "panacea", because it is not only suitable for most plants and land, but also has many functions, such as one of the raw materials of some plastics, laying on the ground to prevent freezing, adding some products such as shampoo and detergent, rain promoter, tooth whitening products and so on.
Of course, in addition to these applications, it can also be used as a feed additive that many people have not thought of, but they are usually only for ruminants. Finally, on the surface, cows are herbivores, but in fact, they can grow strong muscles (protein). Apart from a small amount of protein in the food, the most important thing is that they eat meat every day. These meats are microorganisms that enter the digestive system with food in the rumen, so the number of microorganisms is very important to these animals.