BY: Peter Smith
WA Dept of Agriculture- Karratha
Beef Development Officer
Ph: (08) 9144 2065
pcsmith@agric.wa.gov.au

• What urea does in a cows rumen
• The principles of urea supplementation
• Recommended intake rates
• General feeding principles
• Recipes and mixes

What urea does in cattle rumen

As feed quality declines, rumen ‘bug’ activity and numbers decline, rumen function (breakdown of fibrous material) slows, feed intake declines and animal performance suffers. This is an ever decreasing circle; the poorer the feed quality becomes as the season progresses, the less animals digest and the less they eat of poor quality feed, and so it goes!

Providing an adequate Nitrogen (N) and Sulphur (S) balance in the rumen of cattle grazing poor quality pasture will increase the numbers and activity of rumen ‘bugs’ thus increasing rumen function and the rate that feed breaks down. Although providing a N & S supplement seldom improves the digestibility of the feed eaten it usually increases the amount of feed eaten, by up to 30% or more.

This is a bit like drinking mid strength beer, if you drink more it will work better!

Similarly cattle eat more of the poor quality feed and perform better. This usually relates to losing less weight. N & S supplements are generally most economically provided by feeding urea balanced with sulphur in the form of blocks, loose mixes or in some situations, drinking water.

Why Urea?

• It is very effective at improving the intake of poor quality feed.
• It’s cheap – compared to other protein sources. BUT. It can be nasty!
• Urea can be toxic to ruminants if consumed too quickly

PRINCIPLES OF UREA SUPPLEMENTATION:

The wills and wont's of urea supplementation:

• Will- Increase the intake of dry roughage
• Will- Reduce the rate of liveweight loss
• Won't- Ensure the survival of poor or weak cattle
• Won't- Be well utilised by young cattle less than 4 months old
• May- Result in overgrazing. Cattle supplemented with urea will eat up to 30% or more extra feed.
• May- Kill cattle. Urea is highly toxic to cattle if consumed too quickly.
• May- Not be economically viable. In the current economic climate it may be difficult to justify the cost of supplementary feeding breeders "on a face" unless results include reducing deaths.

In order of preference it is suggested that urea supplementation should be concentrated on weaners and if they are segregated from the main breeder herd, females pregnant to calve for the first time.

Recommended intakes of urea:

Weaners (over 6 months and 150 kg), 20 – 25 g urea a day. One hundred weaners should consume around 50 – 60 kg of 30% urea blocks or mixes each week

Older cattle, 25 – 50 g a day. One thousand breeders should eat between 600 and 1200 kg of 30% urea blocks or loose mix each week. Around 1 kg of 30% urea block or loose mix for each breeder each week is a convenient figure to work with.

Sulphur should always be included in loose mixes at the rate of 5 kg for each 100 kg of urea. This amount of S is also contained in 20 kg of Sulphate of Ammonia. Sulphate of Ammonia is often better to mix and can be useful to control intake of loose mixes.

On phosphorus (P) deficient country up to 3 g of P a day can be added to urea based loose mixes fed to lactating breeders. This is equivalent to 10% Kynofos in a 30% urea mix.

General Feeding Principles:

Water medication or feeding urea and S through the drinking water has a lot of advantages, particularly in situations where a large number of cattle can be supplemented from one medication unit on a reticulation system. Advantages include:

a) Regulated intake of urea and S. All cattle get around the desired intake.

b) Only nutrients required are provided. The majority of ingredients in loose mixes and blocks are basically carriers for the urea and sulphur..

Cattle management practises aimed at reducing numbers to be fed and improving supplement availability to cattle that need feeding most are strongly recommended.

a) Weaning and feeding and managing weaners well.

b) Segregating cows with calves too young to wean and weak cows – usually easier said than done in more extensive situations.

c) Reduce numbers at risk by selectively selling dry cows in better condition that will calve late in the year when they are likely to be a serious survival risk.

Animal cravings. Try to satisfy animal cravings before introducing higher levels of urea.

a) On salt hungry country feed a mix without any urea or a block with a low urea content for at least a couple of weeks before including high levels of urea. This will reduce the risk of urea toxicity of supplement hungry cattle gorging on high urea content supplements.

b) Always commence feeding higher urea content supplements before the introductory supplements run out.

Higher intake: Provided cravings have been satisfied and cattle are not "lick hungry", higher levels of urea, 25 – 30% are generally safer than lower levels; 10 – 15%, in loose mixes. The bitterness of the urea tends to control intakes at these higher levels.

Controlling intakes. Intakes of the same blocks and mixes might vary widely on different areas of properties and between different classes of cattle. There is a lot of debate among animal behaviour specialists regarding the ability of cattle to eat only what they ‘need’ rather than what they ‘like’. I think that cattle often eat different things in different areas because different material in the diet produces different ‘cravings’ or ‘tastes’. Efforts should therefore be made to improve supplement intakes in areas where they are low and reduce them in areas where cattle are eating too much.

Once urea supplementation has commenced supplements should be kept on offer to reduce the risk of gorging by ‘lick hungry" cattle.

Keep records. Get an idea of cattle numbers in various areas and keep records of supplement fed out. A lot of money can be spent on supplements without getting optimum benefit.

Urea content. Supplements containing higher levels of urea 20%+ are usually a lot more cost effective than supplements with lower levels. Remember the aim of the program is to provide cattle with a N & S supplement not a feed of all sorts of other odds and ends that are likely to have little value if N & S are the limiting nutrients in the dry season.

No matter how much water or oil is put in a vehicle it won’t go too well without fuel!

Purchasing supplements:

• Urea supplements should be purchased on the basis of cost per unit of urea and not on the basis of cost per tonne. There is also not much point in purchasing blocks or mixes that cattle will not eat – see above. It is suggested that smaller quantities of supplements are purchased initially to ascertain what, and how much, cattle are likely to eat. This may change from year to year.

• Blocks are usually easier to feed out but are generally more expensive than ‘loose’ or custom mixes. It is also possible to alter the composition of loose mixes to regulate supplement intakes.

• Shop around; always a good idea when spending a lot of money.

Recipes for loose mixes:

These recipes are presented as examples only and may not suit all situations in northern Australia. They are based on research findings and the experience of beef producers from various areas of northern Australia.

WARNING: These recipes contain urea which can be toxic to cattle if consumed too quickly!

Example 1. (Including Phosphorus)

Ingredient %	Starter Mix	Urea Mix
Salt	70	45
Urea (46%N)	-	30
Sulphate of Ammonia (S)	10	10
Kynofos (P)	20	15

Desired intake (100 head /week) Weaners; 50 kg Breeders: 100 kg

Example 2. (No Phosphorus)

Ingredient %	Starter Mix	Urea Mix
Salt	80	60
Urea (46%N)	-	30
Sulphate of Ammonia (S)	20	10

Desired intake (100 head /week) Weaners; 50 kg Breeders: 100 kg

© WA dept of Agriculture December 2002-  This source: http://www.cattlefacts.com.au

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