Introduction
During the extreme drought which Namibia is experiencing at the moment, many farmers have lost cattle and sheep to urea poisoning or what they suspect was urea poisoning. The following article will attempt to give background on what urea is and how it can be used in lick supplementation programs.
Urea is a non-protein nitrogen (NPN) compound. Farmers should remember that urea contains no other useful feed components such as energy, amino acids, minerals or vitamins, therefore it should be used in conjunction with feed components which can supply the needed energy, amino acids, minerals or vitamins and necessary building blocks for microbial protein synthesis. Urea can be used to supply a part of the protein needed in commercial feed & lick supplements. It is important to know that the microbial population needs to be adapted to change these NPN sources into microbial protein, where the animal can digest the protein and use it for growth and maintenance.
Calculations
Farmers should understand that all natural feedstuffs consumed by ruminants contain variable amounts of NPN. The amount of nitrogen in a feed sample is used to determine how much crude protein it contains. Urea can contain from 42% to 46% nitrogen. To work out the amount of crude protein that urea contains a factor of 6.25 has to be multiplied with the percentage of nitrogen, giving a result of 281 or 262 depending on the amount of nitrogen present. Determining the amount of natural protein in a supplement: Subtract the amount of non-protein nitrogen sources from the total percentage of crude protein listed on the feed tag. For example: Crude protein (not less than) 30% - Protein equivalent from NPN 20% = 10% of the feed is natural protein.
Mode of action
Urea is broken down to ammonia during the fermentation process in the rumen. Micro-organisms in the rumen combine the ammonia with products of carbohydrate metabolism to form microbial protein which consists of amino acids. The proteins formed in this way are similar in amino acid content to the proteins available to the animal when the principal source of dietary nitrogen is intact protein or natural protein. -
Adaptation
Dry Season
In the extreme drought that Namibia is facing at the moment where little or no roughage is available, it can happen that animals who are nearly starved can consume too much of a lick which contains urea and this can lead to urea poisoning. Urea inclusion in animals lick or feed should be done gradually and when it has been included in the supplementation of the animal, the animal should receive it every day so the micro-organisms within the rumen stay adapted. If producers decide to use a supplementation lick, they should ensure that that the animals are not salt hungry. The animals can consume too much of the lick which contains urea and this can lead to urea poisoning. To prevent animals from consuming too much of the lick, producers can give a phosphate lick, for example, Futterfos P6 for two to three days before the protein lick is provided which contains higher levels of urea, this should be implemented especially if animals were not given phosphate lick in the green season.- An amount of digestible energy in a feed ration influences how much urea can be digested by the ruminant animals. Starch from grain sources is the best source of energy for urea utilization. Molasses can also be used but as the sole energy source the highly fermentable sugars are used up too quickly and this will decrease the amount of urea that is utilized by the animal.
Wet season
Products which are moist and contain urea will not necessarily be a risk to ruminants. If the urea has dissolved in standing water and ruminants drink the water then this can cause deaths. Caution should be taken in the rainy season when licks with urea are given. Possible lick containers should have coverings or standing water in the lick containers should be removed.
Symptoms -
The following symptoms are characterized by urea toxicity; uneasiness, tremors, excessive salivation, rapid breathing, incoordination, bloating, and tetany. Animals usually die when their blood ammonia level reaches 5 milligrams per 100 milliliters of blood. The rumen pH will rise to about 8, and the normal function of the rumen will cease. Signs of urea poisoning can start as quickly as 10 minutes after the urea has been consumed. In severe cases, animals can die within minutes after the urea has been consumed, but usually, it takes 4 hours for the animals to die.
Treatment
Treatment is the last option and not very effective because of the seriousness of the poisoning. Vinegar can be administered orally (0.5-1.0 liter for a sheep and 4 liters for an adult ruminant. Very cold water can also be given, 10-30 liters for an adult ruminant, this will dilute the urea and suppress the urease activity and will also decrease the uptake of ammonia. The treatment should be administered as quickly as possible after the first symptoms and can then be repeated after 30 minutes.
Feedmaster licks and feeds
All protein licks and concentrates are formulated according to Act 36 of 1947 and if products are mixed according to instructions, the products will be safe for ruminants to consume.
