It’s a (Rumen) Bug’s Life.
Everywhere I go, I see cattle producers with drylick drums out in paddocks where it hasn’t rained. This is excellent as it will boost your dry feed consumption and utilisation by around 10%. It does this by trickling a small amount of readily fermentable carbohydrate and nitrogen (usually in the form of urea) into the rumen to help the rumen bugs work harder.
Urea is a cheap, highly potent source of nitrogen. The nitrogen component can be used as a building block for production of protein by rumen bugs. Urea is around 45% nitrogen which makes it 281% crude protein! It’s potent!
I’ve had a lot of calls lately from producers wanting to buy drylicks with higher levels of urea to get a bit more “bang for their buck”. This makes my knees shake in fear - urea can be toxic at relatively low quantities.
Picture this, you’re a rumen bacterium and it hasn’t rained. Your job every day is to chew through highly fibrous dry stalky grass. Many of your buddies have died as there aren’t the substrates in the rumen, such as readily fermentable carbohydrates or sugars to keep you alive and they’ve been replaced with fungi who are better suited to digesting fibre. Every day is a slow, boring day in the rumen factory.
Then, along comes a dry lick. Yippee! A tiny delivery each day of readily fermentable carbohydrate and nitrogen. It’s like providing all of the factory workers with cake and a sandwich for lunch - they work harder all afternoon and churn through more dry feed.
But what happens if the urea level rises? There’s not enough bacteria left to process the extra nitrogen, and we also aren’t used to it - it’s hard to switch from digesting stalk to digesting protein at a moment’s notice and we just don’t have the capability. The extra nitrogen, in the form of ammonia, floats around in the rumen, crosses the rumen wall and ends up in the bloodstream where it is toxic.
It is sent to the liver, where it is metabolised as quickly as feasible back into urea for excretion by the kidneys. This process can be easily overwhelmed, especially if the animal is losing weight and its liver is already processing body fat to help it stay alive. Illness and death soon follows.
Most of the commonly used dry licks have urea inclusion levels of 8-16%, and this is plenty. If you’re looking for more “bang for your buck”, consider switching to a molasses-based syrup that contains urea and that is appetite limited, or feed whole feeds such as grains or cottonseed.
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