Online Publications


Balancing Rations for Dairy Cows Using Commercial Supplements

Donna M. Amaral-Phillips

Taking time to balance the milking herd ration helps insure that the nutritional needs of the cows are met while minimizing feed costs. Table 1 shows the effects of balancing rations several times a year. In both studies, milk production increased when rations were balanced.

Table 1. Balancing rations increases milk production
Ration balancedMilk production increase per year (lb/cow)
Minnesota - 5 herds monthly+ 1100
Virginia - 4 herds/group 
7 times/year+ 780
5 times/year+ 486
none- 86
Source: L. H. Kilmer. Dairy Profit Series: Nutrition
Iowa State University Extension Publication DY-S-3023

Forage testing is an essential starting point to balancing rations that are profitable and nutritionally sound. Table 2 shows the normal variation in the nutrient content of forages fed to dairy cows in Kentucky. Forages vary in nutrient content from year to year and thus should be tested yearly. Underestimating forage quality will result in unnecessary grain being fed and increased feed costs. Overestimating forage quality will result in cows receiving less nutrients than they need. As a consequence, milk production may be lower than expected.

Table 2. Nutrient composition of various forage fed in Kentucky
Dry Matter (%)Energy (NEL) (Mcal/lb)Crude Protein (%)
Dry Matter Basis
Corn Silage3723 - 690.630.54 - 0.73 8.3 5 - 10
Alfalfa hay8770 - 980.610.40 - 0.7318.713 - 25
Grass hay8970 - 980.440.30 - 0.64 9.0 6 - 20
Kentucky Forage Testing Program

Forages are the foundation upon which a balanced ration is built. Grain mixes are used to complement these forages and provide a more concentrated source of nutrients to meet the high nutritional needs of these cows. Guidelines on the amount of grain mix and percent protein needed in the grain mix should be used as a starting point when feeding dairy cows.

The amount and percent protein needed in the grain mix depends on many factors. These include:

Calculating the Amount of a Commercial Grain Mix To Feed

This example shows the steps needed to calculate the amount and protein percentage of the grain mix fed to the average cow in a herd. Please pay attention to the assumptions made because they affect the amount and kind of commercial grain mix fed.

Step 1:

Gather information about the average cow in the herd (or individual cow). This information includes:

  1. Body weight
  2. Milk production
  3. Milk butterfat test
  4. Average age of the cow
  5. Does the cow need to gain weight to be in proper body condition when she is dried off?

For this example, we will be using a 1300 lb mature Holstein cow producing 65 lb of milk at 3.5% butterfat and we want her to gain 1 lb body weight per day.

Step 2:

Gather information about the forages the cows are consuming. This information includes the nutrient analysis of the forages fed (from your forage analysis sheets) and the amounts of each forage the average cow consumes.

For this example, the average mature Holstein cow consumes:
55 lb corn silage
5 lb alfalfa-grass hay

The nutrient content of these forages on an as fed basis is listed in Table 3.

Table 3. Intake and nutrient composition of forages used in the example
Intake (lb) Energy (NE L) (Mcal/lb)Crude Protein (%)ADF1 (%)Calcium (%)Phosphorus (%)
 as fed basis
Corn silage550.262.7
Alfalfa hay50.5514.
1 ADF = Acid Detergent Fiber

How to convert from dry matter basis to as fed:

Nutrient composition (dry matter basis) X % dry matter

Remember that the nutrient composition expressed on a dry matter basis is a larger number than when expressed on an as fed basis.

Step 3:

Calculate the average cow's requirements for energy (NEL), protein (crude protein), calcium and phosphorus.

Table 4. Calculations for example (Step 3)
 Energy (NEL) (Mcal/day)Crude Protein (lb/day)Calcium (lb/day)Phosphorus (lb/day)
Milk Production20.155.4600.1950.117
(none because mature cow)
1 lb weight gain2.320.320- - - - -- - - - -

The amount of energy and crude protein needed for maintenance is obtained from Table 5 using the section labeled "Maintenance Requirements of Mature Milk Cows." To calculate the amount of nutrients needed for production, multiply amount of the nutrient needed per pound of milk at a particular fat percentage (use Table 5) by the pounds of milk.

For this example: to calculate the amount of energy needed for 65 lb of milk at 3.5% fat test

(0.31 Mcal NEL/lb milk) x 65 = 20.15 Mcal NEL.

First and second-lactation cows need additional nutrients to grow. To calculate the amount of energy, protein, calcium, and phosphorus needed for growth of first-calf heifers, take 20% of the maintenance requirement for each nutrient. For second-lactation cows, the growth requirement is calculated by taking 10% of the maintenance requirement for each nutrient.

Table 5. Daily nutrient requirements for milking dairy cows.
Live Weight (lb)Energy (NEL) (Mcal) Crude Protein (lb)Calcium (lb)Phosphorus (lb)
Maintenance Requirements of Mature Milk Cows1
Nutrients Needed for Each Pound of Milk at Different Fat Percentages
Fat %
Estimated Nutrient Needs for Each Pound of Weight Change
1 lb weight loss-2.23-0.320----------
1 lb weight gain2.320.320----------
Source: Nutrient Requirements of Dairy Cattle. 6th revised edition, 1989. National Academy Press.
1To allow for growth, increase maintenance allowances for protein, energy, calcium and phosphorus by 20% for first-calf heifers and 10% for second lactation cows, (referred to as growth in Table 4. Step 3).

Step 4:

Calculate the amount of energy, protein, calcium and phosphorus provided by the forages. Make sure you use the nutrient analysis on an as fed basis.

Table 6. Calculation for the example (Step 4)
Energy (NEL) (Mcal/day)Crude Protein (lb/day)Calcium (lb/day)Phosphorus (lb/day)
Cow's needs32.046.6720.2480.154
From forages:
55 lb corn silage114.301.4850.0600.038
5 lb hay2.750.7050.0640.011
 ___________________ _____
Total from forage17.052.1900.1240.049
Needed from grain:214.994.4820.1240.105
1 Use as fed nutrient analysis to calculate: Example for corn silage (0.26 Mcal NEL/lb c.s. x 55 lb c.s.) = 14.30 Mcal NEL
2 Calculated by subtracting nutrient provided by forages from the total amount of that nutrient needed by the cow.

To calculate the amount of energy (NEL) obtained from corn silage, multiply the concentration of energy (NEL) on an as fed basis by the amount of corn silage fed (See Table 3, Step 2).

For example:
55 lb corn silage x 0.26 Mcal NEL/lb = 14.30 Mcal NEL

Step 5:

Subtract the amount of energy, protein, calcium and phosphorus provided by the forages from the total amount of energy, protein, calcium and phosphorus needed by the cow. This is the amount of energy, protein, calcium and phosphorus that must be supplied by the grain mix. (For the calculations, see Table 6 in Step 4.)

For this example: The cow needs 32.04 Mcal NEL and 17.05 Mcal NEL is provided by the forage. Thus, 14.99 Mcal NEL (32.04 - 17.05 Mcal NEL) must come from the grain mix in order to meet the cow's energy needs.

Step 6:

Calculate the amount of grain mix and the percentage of protein needed in the grain mix.

A. To calculate the amount of grain to feed, use the following equations.

Mcal NEL needed in the grain mix/Mcal NEL in one pound of grain mix

The amount of energy (NEL) found in commercial grain mixes can vary (range = 0.60-0.80 Mcal NEL on an as fed basis). Ask your feed company representative for the amount of NEL in the grain mix you are purchasing.

For example: If the grain mix contains 0.73 Mcal NEL per pound of grain mix (as fed basis), then:
(14.99 Mcal NEL needed in grain mix/0.73 Mcal NEL/lb grain mix) = 20.5 lb grain mix

Therefore, you would need to feed this cow 21 lb of grain mix to meet her energy needs.

Make sure you know whether the NEL value provided by your feed company representative is on an as fed or dry matter basis. If the NEL value is on a dry matter basis, convert to as fed by using the following equation.

_____ Mcal NEL (Dry matter basis) x 0.89

For example:
0.82 Mcal NEL (Dry matter basis) x 0.89 = 0.73 Mcal NEL

B. To calculate the percent protein needed, use the following equation.

(Pounds protein needed from grain mix/pounds of grain needed) X 100

For this example:
(4.482 lb protein needed/21 lb grain mix) x 100 = 21.3% protein in grain mix

In this example, a 22% protein grain mix would have to be fed to meet her protein needs. (Always round up on the percent protein needed in the grain mix.)

If a 22% grain mix is unavailable from your feed company, you will need to feed a 20% protein grain mix and at the same time feed more pounds of this grain mix to meet the cow's protein needs. To calculate how much grain mix to feed if the highest protein grain mix available is 20% protein use the following equation;
(lb protein needed in grain mix/% protein in grain mix) X 100

In this example:
(4.482 lb protein needed in grain mix/20% protein in grain mix) X 100 = 22.4 lb grain

C. Determine mixture of concentrates to feed

The "Pearson's Square" method is one way of determining the mixture of grain and protein supplement needed to obtain a desired protein percentage. The desired protein percent of the grain mix is placed in the center of the square. Percent of protein in the grain and protein supplement are placed in the two left corners. By taking the difference (diagonally) between the desired protein percent and the percentage of protein in the grain or protein supplement, it is possible to determine the pounds of each to use.

Here, a 25% protein grain mix is made using ground ear corn and a 40% protein commercial supplement.

In this example, 18 parts (40 - 22) out of a total 32 parts would come from ground ear corn, or 56% of the grain mix is ground ear corn.

18 parts = 18/32 x 100 = 56% of mix is ground ear corn

The remaining 14 parts (2208), or 44% of the mix, is 40% commercial protein supplement.

14 parts = 14/32 x 100 = 44% of the mix 40% commercial protein supplement

Thus, a ton batch of this grain mix will contain 1120 lb ground ear corn (56% x 2000) and 880 lb 40% protein commercial protein supplement (44% x 2000).

Step 7:

Check to make sure adequate amounts of calcium, phosphorus, energy and protein are provided by the grain mix.

For example if 21 lb of a 22% protein grain mix is fed, the energy, protein, calcium and phosphorus needs of the cow would be met.

Table 7: Calculation for example (Step 7).
In this example, 21 lb of a 22% protein grain mix is fed.
Energy (NEL) (Mcal/day)Crude Protein (lb/day)Calcium (lb/day)Phosphorus (lb/day)
Needed from grain mix (Step 5)14.994.4820.1240.105
Amounts provided in 21 lb 22% protein grain mix1(Step 6)15.334.6200.2000.141
1 In this example, the grain mix contains 0.73 Mcal NEL lb, 22% crude protein, 0.95% calcium and 0.67% phosphorus on an as fed basis.

Worksheet for Calculating Amount of Commercial Grain Mix To Feed Milking Cows.

Step 1: Collect information about cow.

__________ Average body weight of cow

__________ Age of the cow

__________ Average milk production

__________ Average fat test

__________ Average number of days in milk

__________ How much weight should the cow gain?

Step 2: Collect information about forages fed.

ForageAmount fed per cow per dayEnergy Content (NEL) (Mcal/lb)Crude Protein %Calcium %Phosphorus %
As Fed Basis

Steps 3, 4, and 5: Calculating the amount of nutrients needed from the commercial grain mix.

 Energy (NEL) (Mcal/lb)Crude Protein (lb/day)Calcium (lb/day)Phosphorus (lb/day)
Step 3: Calculate cow's needs
Milk Production....
Weight Gain....
TOTAL (A)....
Step 4: Amount of nutrients from forage
TOTAL (B)....
Step 5:
Amount needed from grain (subtract total A from B)....

Step 6:

A: Calculate amount of grain to feed

Mcal NEL needed in grain mix/Mcal NEL in one pound of grain mix as fed =

B: Calculate percent protein needed.

lb protein needed from grain/lb grain needed (step 6 part A) =

Step 7:

Energy Content (NEL) (Mcal/day)Crude Protein (lb/day)Calcium (lb/day)Phosphorus (lb/day)
Needed from concentrate (step 5)....
Amounts provided in _______lbs ______% protein grain mix....

Equal opportunity statement