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Serving: WI

When Did Manure Get A Dirty Name?

More manure now than there used to be.

by Paul Dyk

When you have livestock, you have manure.

Someone asked me the other day whether all the controversy about new dairy farms is because we have more manure than we used to have. A new farm gets built, a lot of cows are being milked in one location, there must be more manure than we used to have. Right? Well maybe not.

The separation of fact and fiction is extremely important when we think about emotional issues of public health and the relationship to manure. So the first thing we need to do is put down a base line.
To put down a baseline, let’s start with just the dairy cows in Wisconsin. Take a look at the chart. Over the last 85 years, we have gone from about 2 to 2.25 million cows down to about 1.25 million. That should mean about half the manure, right? Well it’s not that simple. Milk production has quadrupled from about 5,000 pounds per cow per year to almost 20,000 pounds per cow per year in Wisconsin in the same 85 years.

So what does that mean for manure production?

First, all cows will produce a base amount of manure whether they give milk or not. The more milk they produce, the more they eat, the more manure they produce. Using some simple equations based on maintenance, milk production, and manure produced, an estimate of total manure produced in Wisconsin was calculated for each year. The result is the purple line; from these simple estimations, manure production is about 39% less than it was in the peak year of 1945.

Is that right?

We likely produce less manure than we used to produce? Yep, cows are more efficient than they used to be. As cows have increased milk production, the amount of manure produced per pound of milk has decreased.

This means we should have less environmental issues than in the past and fewer public relations problems? Well not so fast. Other factors come into play.

Manure is not likely the same now as it was in the 1920s. Its nutrient composition is likely much different. Rations cows are fed are significantly different; protein and minerals are fed much differently than 80 years ago. Rations are even significantly different from 20 years ago. In the 1980s, we often fed diets with 19% protein and .5% phosphorus. Today we feed more than 10% less protein and 30% less phosphorus (depending on the nutritionist). And manure storage and spreading has changed significantly. Manure is now often in the form of liquid manure and spread only a couple times a year. For some geographical areas, this requires different management techniques.

The end result is that before we make quick conclusions about the inevitable byproduct of cows, we need to make sure we know the facts. We need to monitor manure quality and quantity for all our farms if we want to have an intelligent dialogue with the public.

Dyk is the Fond du Lac County Extension dairy and livestock agent.

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