Formulating dairy cow rations

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Source:  University of Minnesota

Quick facts

Formulating rations provides cows with the nutrients they need to stay healthy and optimize production.

  • The basis of a cow’s diet should be high-quality forage.
  • Acid neutral detergent fiber should be at least 18 percent and neutral detergent fiber at least 28 percent of ration dry matter.
  • Balance rations to meet the nutrient requirements for each stage of lactation.
  • Added fat shouldn’t go above 7 percent of ration dry matter.
  • Include vitamins and minerals to meet the cow’s needs.
Guide to formulating dairy cow rations

The ruminant feed pyramid provides the basis for formulating rations.

  • High-quality forages and grains are the base of all diets and will support good milk production.
  • Added fats, rumen undegradable protein and other feed additives are needed by higher producing cows.

The goal of your feeding program should be:

  • To meet the cow’s nutritional needs while maintaining health.
  • To optimize milk production, milk fat and milk protein.
  • Accomplished economically.

Expressing computer ration information

  • A ration analysis reviews the nutrients that each feed adds to the ration.
  • It doesn’t balance the ration and doesn’t correct any nutrient deficiencies or excesses.
  • For an accurate analysis, you must know how much of each feed you give, including the nutrient content.

  • A ration balancer program combines feeds to meet the nutrient needs set for a ration.
  • The nutrient content of the feed determines how much you feed to meet your herd’s needs.
  • A balancer program doesn’t consider feed costs or profit.

Least cost formulation includes:

  • Defining the nutrient needs or constraints for the ration.

  • Finding what feeds need to be combined to meet or exceed these constraints at the lowest cost per pound of dry matter (DM).

Least cost formulations change as feed costs change. The computer will often give an opportunity or break-even cost for feeds not used in the ration.

It’s thought to be a good buy when the price of an unused feed goes below the opportunity price. In this case, reformulate the ration to see how much of that feed you can now use.

A true maximum profit ration program includes:

  • A least cost function.

  • Milk price information.

  • A maximum profit (income over feed cost) for one of the constraints or specifications to formulate on.

In maximum profit, the computer selects feeds and calculates a milk production level to obtain maximum profit.

In least cost or balanced rations, the computer only selects feeds to meet the nutrient needs specified for a given level of milk production.

Rules of thumb for formulating lactating cow rations

Estimated dry matter intake for milking cows

Body weight (lbs) 900 lbs 1100 lbs 1300 lbs 1500 lbs
3.75% milk fat (lbs) Dry matter intake lbs/day
30 26 29 33 37
50 31 35 39 42
60 34 38 42 45
70 37 41 45 48
80 40 44 48 51
90 43 48 50 54
100 50 53 57
100+ 52 56 60

Decrease dry matter intake 0.2% for cows less than 90 days in milk.

Dry matter intake guidelines for dry cows

Body weight (lbs) Far-off (lbs/day) Close-up (lbs/day)
900 16-18 14-16
1100 20-22 16-18
1300 23-26 18-22
1500 27-30 20-24

Far-off (2 to 8 weeks before calving) DMI (lb/day) = 1.8 to 2.0% body weight
Close-up (0 to 2 weeks before calving) DMI (lb/d) = 1.5% of body weight

Three measures of fiber should be evaluated in dairy rations:

  • Acid Detergent Fiber (ADF)
  • Neutral Detergent Fiber (NDF)
  • NDF from Forage (NDF-Forage)

The NDF-Forage is only the NDF from hays, haylages and corn silage.

Ration guidelines for fiber

Measure Lactation stage
Early Mid Late Dry
ADF: minimum 18 20 21 28
NDF: minimum 28 28 32 35
NDF-Forage: minimum 20 21 21 25
NDF-Forage: maximum 24 26 28

Excess fiber in the diet can result in:

  • Low milk production, cows not peaking.
  • Dry matter intake lower than expected.
  • High milk fat percent.
  • Early lactation cows fed too high forage and low energy of rations may be more prone to ketosis and have rapid body weight loss.

A deficiency of fiber can result in:

  • Acidosis, cows going off-feed and fluctuating dry matter intake.
  • Low milk fat percent.
  • Cows not chewing their cud.

Protein level guidelines for rations

Protein Lactation stage
Early Mid Late Far-off dry cow Close-up dry cow
Crude protein, % of dry matter 17-18 16-17 13-15 12-13 15-16
Rumen degradable protein, % of CP 60-65 64-68 64-68 65-68 60-64
Rumen undegradable protein, % of CP 35-40 32-36 32-36 32-25 36-40

Protein check and considerations:

  • One pound of crude protein is required to produce 10 pounds of milk.
  • Heat damaged forages will result in less available protein. Heat damage indicators include:
    • Forage color is dark brown to black.
    • Manure is dark colored and dry.
  • Excess rumen undegradable protein in the ration results in:
    • Lower milk production.
    • Stiff dry manure.
    • Lower dry matter intake.
  • Excess rumen degradable protein results in:
    • Low milk production, high early milk peaks with low milk persistency.
    • High milk urea nitrogen (MUN) levels.
    • Loose manure.

Limit urea to 0.4 pounds per cow daily.

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

Select vitamin and mineral recommendation are:

  • Salt: Cows need 3 to 4 oz of salt per day. Feed cows one ounce plus 1 ounce for every 25 pounds of milk. Salt should be included in the grain mix at 1 percent.
  • Calcium: more than 150 grams/day or .75 to 1 percent of ration dry matter. One percent with added fat in the diet.
  • Phosphorus: about 100 grams or 0.35 to 0.4 percent of ration dry matter.
  • Magnesium: 0.3 to 0.4 percent of ration dry matter.
  • Potassium: 1.0 to 1.5 percent of ration dry matter.
  • Vitamin A: 75,000 to 100,000 IU/day.
  • Vitamin D: 25,000 to 30,000 IU/day.
  • Vitamin E: 400 to 600 IU/day.

Nutrition Management

Feed bunk management

There should be 2 to 5 percent of feed remaining when cows are fed.

Lactating cows need 24 inches of bunk space. Close-up and recently fresh cows should have 30 inches of bunk. If feed is available at all times cows can get by with 18 inches of bunk space.

Cows eat best in the grazing positions and the bunk surface should be smooth.

Ration Formulation

When balancing rations, the reference cow should be at the 75th percentile of the herd. To calculate reference cow, take the average peak milk of older cows and add the daily average of all cows and divide by 2.

Example: Bulk tank average – 60 lbs, peak milk older cows – 86 lbs

(60 + 86) ÷ 2 = 73 lbs of milk to balance for

Two groups: Balance rations at 20 percent above average milk production of each group.

Three or more groups: Balance rations at 10 to 15 percent above average milk production of each group.

Water Intake

Cows should consume 3 to 5 pounds of water per pound of dry matter consumed.

Example: 50 lbs DM intake at 4 lbs of water/lb of milk dry matter intake

= 200 lbs of water/day or 200 ÷ 8 lb/gallon = 25 gallons

Ration Check

All rations should contain at least 1 feed from each category:

  • Forage
  • Grains
  • Protein supplements
  • Mineral
  • Salt

Authors: James Linn, former UMN Extension animal scientist; Michael Hutjens, University of Illinois; Randy Shaver, University of Wisconsin; Donald Otterby, College of Food, Agricultural and Natural Resource Sciences;  W. Terry Howard, University of Wisconsin and Lee Kilmer, Iowa State University