Nutrition Milk or manure?

February 2, 2009 06:00 PM
Jim Linn

Last year, when corn climbed well above $5/bu., many nutritionists turned to high-fiber byproduct feeds to replace some or all of the corn in lactating dairy cow diets.

In subsequent conversations, dairy producers often commented that replacing some corn and soybean meal with byproduct feeds resulted in higher dry-matter intake (DMI) with relatively little change in milk production or milk components.

The conversation then turned into a discussion about what happens to feed in the cow. There are basically three end points for feed nutrients in the cow beyond what is used for maintenance: milk, weight gain and manure.

All three occur to some extent in the cow, and some manure is inevitable. However, when manure excretion is minimized, the highest feed efficiency is attained and the lowest amount of nutrients are excreted, favoring both the environment and return on the feed dollar.

A research paper by Bill Weiss of The Ohio State University provides some insight into the effect that diet and nutrients have on manure output from cows. Go to for a direct link.

Based on this paper, feeding more protein than the animal requires increases manure output. For every 1% unit increase in protein above requirements, manure output increases 2 lb./cow/day!

Also, diets high in fiber lead to more manure excretion as fiber is less digestible than nonfiber carbohydrates. A 1% unit increase in neutral detergent fiber content of the diet increases manure output 0.5 to 1 lb./cow/day. Many common byproduct feeds (corn gluten feed, distillers' grains, soy hulls and wheat midds) are higher in both protein and fiber than corn, which contributes to more manure output.

In general, as fiber content of a diet increases, the energy content of the diet decreases and DMI also will decrease. However, the small particle size of most feed byproducts doesn't restrict DMI, so when byproduct feeds replace corn, cows are able to increase DMI enough to sustain milk production. The end result is a lower feed efficiency with more manure.

Profitability and the environment are two key areas that you and your nutritionist will have to be concerned with this year. Keeping feed costs down will be important to maintaining profitability on dairy farms, but focusing solely on cost without consideration as to how efficiently feed is utilized by the cow will be counterproductive and reduce profitability.

As we move through 2009 with volatile milk and feed prices, it will be important to watch not only for good feed buys, but also the production response from those feeds. Allowing cows to eat for maximum milk production will be the most profitable approach as long as cows convert feed to milk at efficiencies above 1.55 lb. of milk per pound of feed dry matter consumed. What you need to avoid is to be paying for feed that is simply converted into manure.

Bonus content:

Click here to view Ohio State research on feed/manure relationship.

Click here to read this article in Spanish.

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