Urea as a Feed Additive
Urea can be a good way of adding protein and balancing an animal's diet when it is fed lots of supplements, particularly poor quality supplements.
Nevertheless, you need to be careful with it-overdoses can poison and kill livestock.
Trials show you need to feed it for more than a month to gain any economic advantage, because it takes that long for an animal's rumen to adjust to it.
Why Balance is Important
Any animal being fed large quantities of supplements needs a balanced diet if it is to at least maintain condition.
For sheep and cattle, this includes soluble carbohydrates, which provide energy, and less soluble carbohydrates, or roughage, as well as protein and bulk so the animal feels full.
Urea can be used to improve the digestibility or feed value of low quality feeds in two ways.
Feed Urea to Stock
Dietary N (urea) is converted to ammonia in the rumen of sheep and cattle. Rumen microorganisms use ammonia to make microbial proteins, which are then digested by the animal.
Poor quality roughages, eg cereal straws or poor quality hay that contains a lot of stem but not much leaf, can be deficient in crude protein (N). Insufficient N in the diet means rumen microorganisms cannot make enough microbial protein for maintenance or growth of the animal.
Feeding urea in the diet provides N to the rumen microorganisms and more microbial protein is produced, improving the supply of protein to the animal. Molasses is a good carrier for urea because the soluble sugars in molasses provide an instant source of energy to the rumen microorganisms, improving the efficiency with which they can turn urea into microbial protein.
Urea converts to ammonia when fed directly to stock. Micro-organisms in the gut absorb the ammonia and convert it into proteins, which are then easily absorbed. It takes 20-30 days for the rumen to adjust to urea.
On its own, it is a bitter and unpalatable feed. Combining it with something like molasses or grain has two advantages. First, it makes the urea more palatable and second, the molasses or grain will provide the necessary energy to assist the digestive process.
Poisonous! Beware!
Urea is toxic in excess. It should not be fed to animals less than 12 weeks of age and should be fed at a rate no greater than 15 gm of urea per 50 kg LW in a single feed to animals not used to it. It should never be fed to hungry animals; instead, roughage should be offered first to fill the stomach. Urea must be introduced gradually to animals over a period of two to four weeks to allow the stomach to adjust.
Important Points
It is important that reasonable care is taken in determining the correct ration of urea according to the livestock being fed. If this is done and is carried out over a reasonable length of time, there should be economic benefits in its use.
- The addition of 1 kg of sulphur to 1 kg of urea may result in added benefits.
- It is essential that adequate levels of energy, in the form of molasses or grain plus minerals and vitamins, be fed in conjunction with urea.
- Urea levels for sheep per animal per day are:
- 5 gm fed with 100 gm to 250 gm of grain or 15 gm to 60 gm of molasses. The required amount of urea may be dissolved in water and sprayed onto the daily grain.
- 700 gm of limestone per 50 kg of grain is desirable.
- Urea levels for cattle when feeding roughage or as a supplement for pasture are:
- 115-150 gm per adult per day (450 kg LW animal)
- 60-70gm per rising 2 year old per day.
- 45-60gm per yearling per day.
- It is desirable to mix the urea with four times its weight of molasses or cereal grain.
- A molasses urea mixture for spraying onto low quality roughage is 1000 kg of roughage sprayed with 35-40kg of urea which has been dissolved in 70-80 litres of water and 30 kg (23 litres) of molasses.
- Commercial mixtures of molasses and urea are now available, providing a safer alternative to mixing your own urea/molasses mixes. Commercial mixes can be fed in troughs, or with lick drums or lick balls.
Stuart Ford
Agricultural Consultant
Agriculture New Zealand
Timaru
Contact for Enquiries
Manager
North Island Regions
Sector Performance Policy
MAF Policy
Hamilton
NEW ZEALAND
Phone: +64 7 957 8313
Contact this person
