Steps for Evaluating a Pasture Based Ration

Review hay and grain based ration first (Evaluating Hay Grain Diets).

Rations can be evaluated on either an as sampled or dry matter basis. The hay & grain ration evaluated on this site was developed using as sampled results. This was possible because hay and grain are similar in dry matter content, which in the absence of analytical values is assumed to be about 90%. Since pasture is wetter and lower in dry matter (20-25%), it is simpler to balance the ration on a dry matter basis.

There is also the challenge of estimating daily pasture consumption. Most livestock species eat to satisfy a need for total pounds of dry matter. Knowing the predicted total intake, will enable you to estimate total pasture intake.

This ration will be balanced on a dry matter basis. (Go to as sampled vs. dry matter basis for more information.)

The horse in this example is an 1100 thoroughbred mare, lactating, with a two month old foal. Although all components should be evaluated, for simplicity’s sake, we’ll just focus on crude protein (CP).

1. Refer to the Nutrient Requirement Tables (NRC) to determine the daily protein requirements. Requirements are based on body weight, activity level, growth stage and reproductive status.
Protein required for 1100 lb. horse, lactating with a two month old foal = 1427 grams /day.
2. Feed consumption
  1. Weigh amounts of hay and grain fed.
    Hay = 8lbs.
    Grain = 12 lbs.
  2.  Calculate lbs. of dry matter supplied from the hay and grain.
    As fed (lbs) % Dry Matter Dry Matter (lbs)
    Hay 8 x 90/100 = 7.2
    Grain 12 x 90/100 = 10.8
    Total x = 18.0
  3.  Go to the Dry Matter Intake Table and find estimate of total daily dry matter intake. For this horse, estimated daily intake is 2.3% of body weight. Calculate total daily lbs. of dry matter consumed:1100 x (2.3/100) = 25.3 lbs. of dry matter.
  4.  Estimate pasture consumption as follows:
    Total intake 25.3 lbs.
    Hay – 7.2 lbs.
    Grain – 10.8 lbs.
    Difference 7.3 lbs.

    Pasture consumption will be approximately 7.3 lbs. of dry matter to satisfy the total daily need for dry matter. If the pasture is 25% dry matter, the as fed amount (or adding the water back in), equals 29.2 lbs. (7.3/(25/100)). We’ll continue to use the dry matter figures to evaluate this ration.

3. Calculate grams of CP supplied:
All values as sampled
Lbs. fed CP,% CP, grams/lb. CP, grams fed
Hay 7.2   6.7 30.4 219
Grain  10.8 13.3 60.3 651
Pasture  7.3 19.0 86.2 629
Total 1499
4. Calculate deficiency or excess:
Daily CP supplied 1499
Daily CP required 1420
Difference +79

This ration supplies excess protein. Pasture, especially lush, early season pasture, is often high in protein. This usually results in the total ration being high in protein. In this example, lactational demands place a premium on protein in the diet and the overage will insure that her daily protein needs are met.

Work with your nutrition professional or veterinarian to monitor body condition and other factors. Make adjustments as advised.

This is a simple illustration of using analytical values to evaluate your ration. Other factors such as body condition, health history and environmental factors should be taken into account to best design a sound ration for your horse. Consult with your nutrition professional or veterinarian to help you formulate a ration designed to insure the health and longevity of your horse.