By mid-September, the slurry tank at mark and Mike Wenger’s is usually full. However, this year it was a good 5 feet below capacity. Given the diameter of the tank, a 5-foot difference in height translates into 35,160 cubic feet.
According to one of the farm’s feed advisers, Don Sanders of Agri-King, some of the reduction in the Wengers’ tank may be attributable to a lack of rainfall this summer, but most of it is due to improved feed efficiency.
The Wengers, who run a 170-cow herd near Brodhead, Wis., definitely have made improvements in feed efficiency. They bought a kernel processor to break up corn kernels when chopping silage, thus making the grain more digestible.
Currently, their cows produce 1.5 pounds of milk for every
1 pound of dry matter intake, and they would like to improve it even further to 1.6.
Greater feed efficiency can result in a sizeable difference in the amount of manure that has to be stored and handled. It’s a difference that the Wengers — and most other dairies — can see.
A huge difference
What goes into the cow as feed comes out either as milk, feces, gas or urine — assuming she is not pregnant or gaining bodyweight, says Mary Beth Hall, dairy nutritionist at the University of Florida.
Therefore, with higher efficiency, more of the feedstuffs are digested to produce milk than waste products.
For a 300-cow dairy, with average daily milk production of 80 pounds per cow, an improvement in feed efficiency from 1.4 to 1.6 would result in a 116,055-cubic-foot reduction in wet manure volume over a year, according to Leendert van den Broek, director of dairy business for Trouw Nutrition in Highland, Ill. (Please see the info graphic below for more details on the assumptions used by van den Broek in making this calculation.)
An improvement in feed efficiency can influence your manure output tremendously, van den Broek says.
As the volume of wet manure decreases, so, too, do the nutrients like nitrogen and phosphorus that pose pollution concerns.
Assume, for a moment, that a herd improves its feed efficiency from 1.4 to 1.6, with an attendant increase in daily milk production from 70 pounds to 80 pounds, on average. Despite higher milk production, daily dry matter intake remains at 50 pounds. Ration protein is about 17 percent, and phosphorus content of the diet is 0.39 percent. Cows produce milk with 3 percent true protein and 3.5 percent butterfat.
Given those assumptions, an improvement in feed efficiency from 1.4 to 1.6 will result in a significant drop in the amount of nitrogen and phosphorus excreted, according to the University of Florida’s Mary Beth Hall. Specifically, she says, it will result in:
A 4.6-percent drop in the amount of nitrogen excreted — from 467.6 grams (or 1.03 pounds) per cow per day to 446.3 grams.
A 6.8-percent drop in the amount of phosphorus excreted — from 59.9 grams per cow per day to 55.8 grams.
A difference you can see
Bob Parrell, who runs an 80-cow dairy near Belmont, Wis., agrees that it is worthwhile to strive for greater feed efficiency and less manure output. He has even pushed up the harvest schedule on his alfalfa in order to get forage with a higher digestibility.
And the difference, so far, is noticeable. Now, when Parrell hauls manure out of his stall barn, he finds that the manure volume in the box spreader is about 4 inches lower than it was before.
There’s “definitely a difference,” he adds.
What a difference!
over the course of a year, a sizeable reduction can occur in the amount of manure that needs to be stored and handled — thanks to an increase in feed efficiency. For a 300-cow dairy, the reduction can add up to 116,055 cubic feet, based on the following assumptions:
Herd improved from a feed efficiency of 1.4 to 1.6.
Average milk production remained at 80 pounds.
Average dry-matter intake dropped from 57 pounds per day to 50 pounds to support the same milk production at greater feed efficiencies.
No change in average water intake.
Dry-matter content of the manure dropped from 10.5 percent to 9.5 percent with greater feed efficiency.
Wet manure production drops by 63 pounds per cow per day with greater feed efficiency and less dry-matter intake.
To illustrate what 116,055 cubic feet looks like, we took three houses, each with a surface area of 1,700 square feet on the first floor, and used the first 21 feet in terms of their height.