Section 4 – Manure Production

This section will help you estimate the amount of manure and manure nutrients your livestock produce each year. This information will be necessary to design the volume of manure storage needed as well as the amount of land needed for manure nutrient utilization.

To complete this section, you will need to know:
• The number of each species and type of animal being fed
• The average weight of each type of animal while it is on the farm or AFO
• The number of days the animals are at the site
• The type of manure handling system

You can copy this section and fill in your own information and calculations in the spaces below the examples.

Calculating Manure Production

Step 1: Calculate average animal weight
(Incoming weight + outgoing weight) ÷ 2

Example: Steers are started on feed at 650 pounds and fattened to 1200 pounds. (650 + 1200) ÷ 2 = 925 lb. average weight

Step 2: Using Table 1, find the book values for manure nutrient production for each type of animal.

Example: The above steers are fed a high energy diet. From Table 1, these steers will produce 0.82 cubic feet or 51.2 pounds of manure per 1000 pounds of animal per day containing 0.30 pounds of nitrogen (N) and 0.21 pounds of phosphate equivalent phosphorus (P2O5).

Step 3: Calculate manure nitrogen production.

Example: In the above example, 800 steers are fed for 165 days in an open lot.
(800 steers x 925 lb/steer) = 740,000 lbs.
740,000 lb x 165 days x 0.30 lb/day/1000 lb = 36,630 lb. N production

Step 4: Using Table 2, calculate the nitrogen available in the manure when it is removed from the feedlot. (Note: Nitrogen has gaseous forms which can be lost due to volatilization so manure nitrogen values must be adjusted according to the method of manure storage and handling.)

Example: From Table 2, approximately 50% of the manure nitrogen remains after the manure pack is removed from an outdoor open feedlot.
36,630 lb. x 0.5 = 18,315 lb. of manure nitrogen to be utilized

Step 5: Calculate manure phosphorus production.

Example: Using the above example:
740,000 lb x 165 days x 0.21 lb/day/1000 lb = 25,640 lb P2O5

Note: If a liquid manure system is being used to collect all the manure, the necessary storage volume can be calculated using Table 1.

Example: 740,000 lb x 165 days x 0.82 CF/day/1000 lb = 100,120 Cubic Feet or Cubic feet ÷ 27 = 3,700 Cubic Yards