Formulating dairy cow rations

Quick facts

Formulating rations provides cows with the nutrients they need to stay healthy and optimize production. You can formulate rations by hand or with the help of a computer.

Key tips for formulating rations

  • A cow’s dry matter intake should be a minimum of 40 percent forage and no more than 60 percent grain
  • Acid neutral detergent fiber should be at least 18 percent and neutral detergent fiber at least 28 percent of ration dry matter.
  • Early lactation cows need 17 to 18 percent protein in their ration.
  • Added fat shouldn’t go above 7 percent of ration dry matter.
  • Include a calcium-phosphorus source in the grain mix at 1 to 2 percent.

Formulating rations allows you to feed your animals efficiently. It provides animals a reasonable amount of food containing all the nutrients they need. You can formulate a ration with the help of a computer or by hand. Computers provide a more complete analysis of nutrient profiles in rations and also includes economics.

Expressing computer ration information

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Rules of thumb for formulating lactating cow rations

Know the dry matter intake of your lactating cows. Use table 1 as a guide.

Table 1. Determining dry matter intake

Body weight (lbs)
Milk 900 1100 1200 1300 1500
(lbs/day)* Dry matter intake (% of body weight **)
20 2.6 2.3 2.2 2.1 2.0
30 3.0 2.7 2.6 2.5 2.3
40 3.4 3.1 2.9 2.8 2.5
50 3.8 3.4 3.2 3.1 2.8
60 4.1 3.7 3.5 3.4 3.1
70 4.6 4.0 3.8 3.6 3.3
80 5.1 4.3 4.1 3.8 3.5
90 - 4.7 4.4 4.1 3.7
100 - 5.0 4.7 4.4 3.9

* Fat-corrected milk = (milk lb ×0.4) + (fat lb ×15)
** Intakes may be up to 18 percent less for early lactation cows

Total dry matter intake (DMI) of the ration should consist of:

  • At least 40 percent forage DM or about 1.5 percent of the cow’s body weight (BW)

  • No more than 60 percent grain DM or 2 percent of BW

    • Feed 1 pound of grain per 3 pounds of milk if the cows produce between 10 and 70 pounds of milk daily.

    • Feed grain at 1 pound per 3.5 pounds of milk if the cows produce over 70 pounds of milk daily.

Acid and neutral detergent fiber content

Acid detergent fiber (ADF) should be at least 18 percent in ration DM. Nineteen to 20 percent is ideal, especially when you’re feeding fat

Neutral detergent fiber (NDF) should be at least 28 percent of the ration DM. Forages should account for 75 percent or more of the total ration NDF (1.2 percent of body weight or 21 percent of ration DM).

Protein and nonprotein nitrogen

Make sure the ration meets the cows’ protein needs (16 to 18 percent in early lactation rations). A low rumen degradable protein source may be good in early lactation rations for high producing cows.

Limit urea to 0.4 pounds per cow daily. Don’t feed more than 0.2 pounds daily to cows in phase 1 and 2.

Fat

Total fat should not go above 7 percent of the diet DM. No more than 2 percent added fat should be from any one of these sources: animal, vegetable or rumen inert.

When feeding fat, increase the following in the ration DM.

  • Calcium to 0.9 to 1 percent

  • Magnesium to 0.3 percent

  • ADF to 20 percent or more

Minerals and vitamins

Salt should be included in the grain mix at 1 percent. Another option is feeding salt at the daily rate. Individual cows need 1 ounce for maintenance plus 1 ounce for every 30 pounds of milk.

A calcium-phosphorus mineral source should be included in the grain mix at 1 to 2 percent. Another option is feeding these minerals near a rate of 1 ounce per 10 pounds of milk.

Supplement vitamins (A, D and E) and trace minerals in the ration to meet the cows’ needs.

James Linn, former Extension animal scientist -dairy nutrition; Michael Hutjens, Emeritus professor, University of Illinois; Randy Shaver, professor, University of Wisconsin; Donald Otterby, former professor, College of Food, Agriculture and Natural Resource Sciences;  W. Terry Howard, former Extension Dairy Specialist, University of Wisconsin and Lee Kilmer, Emeritus professor, Iowa State University

Reviewed in 2018

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