Don't Fear Your Food: Using Antibiotics as Growth Promotants

This is the last blog post in my series on antibiotics.  If you look back, you'll recall that we have already covered the use of antibiotics to prevent disease and the use of antibiotics to treat and control disease.  Today we'll be talking about the use of antibiotics to promote growth in feeder cattle (cattle that will be slaughtered for meat).  I've pondered for a long time, trying to think of the best way to approach this.  I could approach it from a strictly personal viewpoint, telling you what we do on our farm.  Or, I could approach it from a scientific viewpoint, explaining exactly what these antibiotics do to promote growth within the animals.  I think I'll opt for the middle road, though: I'll tell you what we do, why we do it, and how it works in simple terms.

What Do We Feed Our Cattle?

Here at Ehrenholz Farms, we feed something called monensin to our feeder cattle.  Monensin (also called Rumensin, which is a brand name) is an ionophore and it is fed with the grain (for our cattle either oats or barley).  When we feed it, we have to make sure that we feed the correct ratio of grain to monensin.

When we feed the monensin, we don't just feed pure monensin mixed in with the grain.  I don't even know if it's possible for farmers to get pure monensin (monensin sodium).  The monensin we get is an ingredient in the protein supplement that we feed to the feeder cattle (because protein is a pretty important component of their diets).

The tag that comes with every bag of supplement specifies how much of the supplement should be fed to a calf based on the calf's body weight, and based on how much grain the supplement is mixed with.  For example, the tag tells me the one 300 kg calf should be fed 0.38 kg of supplement per day, and if we were feeding 900 kg barley, we should add 100 kg supplement to the barley and then feed that 300 kg calf 3.8 kg of that mixture.  We don't have nearly enough calves to feed 1,000 kg of feed per day, but we do know that we can mix the supplement with the grain in a 1:9 ratio by weight, so we figure out how much grain we are feeding, and then we know how much supplement to use.  What tools do use to figure that out?  We use good old fashioned pails, a scale, and a calculator (or Dad's head).

A sample of the protein supplement we feed to our cattle and the tag that comes with it to give us feeding instructions.

Why Do We Feed Monensin to Our Cattle?

We feed monensin to our cattle because it helps our calves to be more feed efficient (they grow faster on the feed we give them and use the feed more efficiently, with less waste) and because it has an added benefit of making them more environmentally friendly.  Because of the way it works, monensin also cuts down on the amount of gas produced in the rumen (one of the four sections of a cow's stomach), which may reduce bloat (a potentially fatal condition).

How Does Monensin Promote Growth in Cattle?

As I mentioned earlier, monensin is an ionophore.  Ionophores are classified as antibiotics, but they are not related to human medicine or to the antibiotics we typically use to  treat, prevent, and control disease (although monensin can be used to prevent coccidiosis, a disease that can affect calves of a certain age).

Ionophores work by suppressing certain microbes that live in the animal's rumen.  Since those microbes are suppressed, the microbes that are not affected are able to compete better to increase in number in the rumen.  The microbes that are suppressed are less efficient at breaking down food.  The useful products produced by these microbes are low in energy and carbon (so the animal has less energy and less carbon to use for growth).  The waste product produced by these microbes is methane, which we all know is a major greenhouse gas, and is released by burps and from the rear of the animal.  So what about the microbes that increase while the other ones are being suppressed?  They are far more efficient at breaking down food, putting more energy and carbon into the useful products, and releasing less carbon (and therefore less methane) as waste.  This means the animal has more energy and carbon to use for growing.

How cool is that?!  Not only are there different kinds of microbes that break down food differently, but we are able to control those microbes to help the calves grow more quickly and be environmentally friendly!

I know I probably haven't answered all of your questions on this topic, so feel free to check out the "Further Reading" section and do your own research on this.  And, as always, feel free to leave a comment below or contact me with any questions about how I use antibiotics on my farm.

Further Reading

Explaining Growth Promotants Used in Feedlot Cattle
Worried About Antibiotic Use and Resistance in Cattle?
Canadian Food Inspection Agency: Monensin Sodium
Application of Ionophores in Cattle Diets
The Trials and Troubles of Feeding Monensin to Cattle
Rumensin - Efficacy and Toxicity in Beef Cattle