A cheap way of guaranteeing a constant source of protein throughout the year for the beef cattle raising industry in tropical and subtropical zones is to provide urea mixed to the feed of salt given to the cattle, above all in the dry season, when there is a shortage of pasture. With this food supplement, which turns into protein in the animal’s stomach, after a series of chemical reactions, the herd reaches the ideal moment for slaughter in half the time. The problem is that, if the breeder get the dosage wrong for the protein supplement, there will be intoxication from ammonia.
This is a substance that comes from urea and is hard to control, and it can kill cattle in a few hours, from cardiac arrhythmia and arrest. Now, the good news: a new therapeutic procedure for this kind of problem, simple and about ten times more efficient than the standard treatment, has been successfully developed and tested by a team of veterinarians from the University of São Paulo (USP).
The researchers found that the joint administration of a hydrating solution, usually a saline solution and a diuretic successfully reduces the degree of intoxication and saves the majority of cattle that, with an excess of ammonia, go into a convulsion, a critical stage which leads to an imminent risk to life. If the use of amino acids from the urea cycle are added to the above procedure, the results of the new therapy are usually even better. “But the use of amino acids, an expensive product, is not indispensable, in this alternative treatment”, guarantees Enrico Lippi Ortolani, from USP’s Faculty of Veterinary Medicine and Zootechny, who coordinated the studies into intoxication by ammonia.
“Just with the hydrating agent and the diuretic, it is possible to get round the problem”. Last month, Ortolani took part in the 22nd World Buiatrics Congress , in Hannover, Germany, where he set out the alternative treatment. The usual procedure to try to neutralize the intoxication, the effectiveness of which, according to Ortolani, leaves much to be desired, is to administer acetic acid, better known as vinegar, to the animals that are showing the problem.
The use of the alternative treatment sparks off a crucial action for an organism intoxicated by ammonia: urination. By means of a series of experiments, with funding from the National Council for Scientific and Technological Development (CNPq), the veterinarian’s team found that, even without being subjected to any treatment, animals with a greater capacity for urinating had, spontaneously, a better chance of escaping from the intoxication alive. This is because the concentration of ammonia (and urea) in urine is directly proportional to the quantity of liquids filtered by the kidneys and eliminated by the body.
It was also found that the pH (the level of acidity, or basicity) of the blood and urine of animals that passed a lot of water was slightly lower than 7 (slightly acid), less than for the animals that passed little water. There was a clear relation between these parameters: the lower (less acid) was the pH of the urine, the more ammonia was eliminated by this means. When reaching a pH higher than 7 (basic or alkaline), the cattle’s fluid starts to favor the absorption of the ammonia by the bloodstream, which leaves the way open for intoxication.
By proposing the use of a hydrating agent, associated with a diuretic, as a new therapy for this condition of intoxication, Ortolani was therefore trying to produce, temporarily, in all the animals with an excess of ammonia the same kind of natural protection from this substance which would otherwise remain a privilege for a few animals. During her studies for a master’s degree, veterinarian Sandra Satiko Kitamura found that some 60% of the rats intoxicated by ammonia survived this clinical condition with the use of a diuretic and a hydrating solution, against only 6% of the rodents that had not received any treatment. “In experiments with 25 head of cattle with convulsions, in which we had brought about an intoxication similar to what happens in the field, we managed to turn the problem around in all cases, with the new therapy”, says Ortolani. “We didn’t lose a single animal”. One hour after having received the hydrating solution and the diuretic by intravenous injection, the animals treated had already eliminated about 30% of the ammonia they had received. In conventional treatment, this level is lower than 3%.
A high concentration of ammonia sets off a sequence of events that leads to the animals’ death, unless quickly controlled. To start with, the excess of this substance depresses the intoxicated cattle, and makes it difficult for them to remain standing. The animal feels its muscles tremble and nervous perturbations, as this substance interferes with its brain, and it ends up falling down. It slobbers a lot, has difficulty in swallowing, and becomes dehydrated.
Ammonia causes water to build up in the lungs, where there is an edema (accumulation of fluid). “The rumen stops working, swells up and presses on other organs”, Ortolani explains. The start of convulsions is a sign that, unless something is done to reverse the condition of intoxication, the loss of that member of the herd is imminent. With the new therapy, these symptoms are controlled in less time. “The animals treated with a hydrating solution and a diuretic recover movement in their rumen and their appetite more quickly, and stand up sooner”, says Sandra. The edema in the lung is also more easily resolved.
The existence of ammonia in the animal’s rumen is indispensable for the urea to become a source of protein. In cattle, as with sheep, the rumen is the part of the stomach where the food is digested, with the help of enzymes produced by microorganisms that live there in symbiosis. When it reaches the rumen, the urea is transformed by the action of an enzyme called urease, which gives rise to ammonia and carbon dioxide. From the ammonia, bacteria in the rumen synthesize proteins, which will enrich the cattle’s diet.
The so-called urea cycle is something that is usually beneficial for livestock raising. Sometimes, though, some problem occurs in the system – a change in the pH in the rumen, difficulty in swallowing, lack of balance in the urea/feed mixture – and the liver and the blood are no longer able to succeed in neutralizing the presence in excess of the ammonia in the rumen. It is then that intoxication occurs.
To avoid the excess of ammonia in cattle, the quantity of urea (a solid in the format of white crystals) added to the food for the cattle should not exceed 1% of the dry matter of the feed, or 3% of the concentrate given to the animals. In ruminants not used to this food supplement, there should be a process of gradual adaptation to the addition of protein. Otherwise, there is a great risk of intoxication. When the supply of urea is interrupted, the process of adaptation has to be started again. If this is not done, intoxication from ammonia may occur. That is to say, any slip up in the use of this cheap source of protein, and the animals may fall sick.
As the gains with the use of urea are great – the animal reaches its ideal weight for slaughter in three years at the most, instead of the traditional five years -, Brazilian cattle breeders, who own about 160 million head of cattle, one of the largest herds in the world, are turning to more and more to this food supplement. In this context, a more effective treatment against intoxication from ammonia , like the one proposed by Ortolani, is of fundamental importance to those who are working with beef cattle.Republish