Pennsylvania's Nutrient Management Act (Act 38): Who Is Affected?

Reviews how to calculate the animal density of an agricultural operation to determine if it is a Concentrated Animal Operation (CAO) and thereby required to develop and implement an Act 38 nutrient management plan.

In spring 1993, the Pennsylvania legislature passed and the governor signed the Nutrient Management Act (Act 6) into law. The regulations implementing this law went into effect in 1997. In 2002 the State Conservation Commission began an effort to revise these regulations. In summer 2005, the Pennsylvania legislature replaced Act 6 with Act 38 as part of the Agriculture, Communities, and Rural Environment (ACRE) initiative. The new regulations, now falling under the new Act 38, were finalized in 2006 and went into effect in October of that year.

These revised regulations include several significant changes in the state’s nutrient management program, including changes to who is affected by the regulations. This fact sheet addresses the question “Who is affected (regulated) by this legislation and regulations?”

Concentrated Animal Operations

The act states that “concentrated animal operations” will be required to develop and maintain a nutrient management plan. Concentrated animal operations (CAOs) are defined as agricultural operations where the animal density of all livestock on the farm exceeds 2 animal equivalent units (AEUs) per acre on an annualized basis. This animal density criteria has not changed in the new regulations; however, two significant changes were made. First, the definition now includes all livestock, including nonproduction animals such as horses used for recreation and transportation. Second, an operation with less than 8 AEUs is not considered to be a CAO regardless of the animal density.

Animal Equivalent Units (AEU)

An AEU is 1,000 pounds of live weight of any animal on an annualized basis. Annualized means that if animals are not present on an operation for a whole year, the animal units are adjusted for the proportion of time during the year that animals are present on the operation. The calculation involves determining the number of AEUs of all animals on the farm based on the number of animals and their average weights and then adjusting that for the actual number of days (out of 365) that the animals are on the operation. To determine the number of AEUs on a farm, the following formula can be used for each type of animal and then added together to get the total AEUs on the farm:

AEUs for each type of animal = [average number of animals on a typical day that the animals are there × animal weight (lb) ÷ 1,000] × [number of days the animals are on the operation per year ÷ 365]

Table 1 lists standard animal weights that are used to calculate AEUs. It is strongly suggested that these standard animal weights be used for this calculation. However, if the farmer has records of actual weights of the animals on the farm, these may be used to determine the appropriate animal weight to be used for this calculation if the records are complete enough to justify the use of the nonstandard weights. Note that for growing animals, an average weight for their growth over the year is used. For example, for broilers that grow from 0.09 to 5.9 pounds per animal over the growth cycle, the average weight would calculate to be 3.0 pounds per animal.

Table 1. Standard animal weights used to calculate animal equivalent units to identify concentrated animal operations.
Type of Animal Standard Weight (lbs)
during Production (range)
Holstein/Brown Swiss
Cow 1,300
Heifer: 1–2 yr. 900 (650–1,150)
Calf: 0–1 yr. 375 (100–650)
Bull 1,500
Cow 1,100
Heifer: 1–2 yr. 800 (575–1,025)
Calf: 0–1 yr. 338 (100–575)
Cow 900
Heifer: 1–2 yr. 600 (400–800)
Calf: 0–1 yr. 225 (50–400)
Bull 1,000
Nursery pig 30 (15-45)
Wean to finish 140 (45-265)
Grow finish 155 (45-265)
Gestating sow 400
Sow and litter 470
Boar 450
Layer: 18–65 wk. 3.10 (2.75–3.45)
Layer: 18–105 wk. 3.15 weighted avg.
Layer, brown egg: 20–65 wk. 3.8 (3.3–4.3)
Layer, brown egg: 20–105 wk. 4.00 (3.3–4.7)
Pullet: 0-18 wk. 1.42 (0.08–2.75)
Broiler, large: 0–53 days 3.0 (0.09–6.0)
Broiler, medium: 0–35 days 2.3 (0.090–4.5)
    Male: 0–7 wk.
    Female: 0–9 wk.
3.54 (0.09–7)
Turkey, tom: 0–18 wk. 20.0 (0.12–40)
Turkey, hen: 0–12 wk. 7.1 (0.12–14)
Duck: 0–43 days 3.56 (0.11–7)
Guinea: 0–14 to 24 wk. 1.9 (0.06–3.75)
Pheasant: 0–13 to 43 wk. 1.53 (0.05–3)
Chukar: 0–13 to 43 wk. 0.52 (0.04–1)
Quail: 0–13 to 43 wk. 0.26 (0.02–0.5)
Calf: 0-8 mo. 300 (100-500)
Finishing: 8–24 mo. 950 (500–1,400)
Cow 1,400
Bull 1,500
Calf: 0–20 wk. 270 (95–445)
Larger Breed Sheep
Lamb: 0–1 yr. 80 (10–150)
Ewe 175
Ram 225
Smaller Breed Sheep
Lamb: 0–1 yr. 50 (10–90)
Ewe 150
Ram 185
Meat Goats
Kid: 0–1 yr. 65 (5–125)
Doe 150
Buck 200
Dairy Goats
Kid: 0–1 yr. 45 (5–85)
Doe 125
Buck 170
Miniature Horses and Miniature Donkeys
Foal: 0–6 mo. 35 (25–45)
Weanling: 6–12 mo. 60 (45–75)
Yearling: 12–24 mo. 100 (75–125)
Two-Year-Old: 24–36 mo. 150 (125–175)
Mature 200
Ponies and Donkeys
Foal: 0–6 mo. 65 (30–100)
Weanling: 6–12 mo. 150 (100–200)
Yearling: 12–24 mo. 300 (200–400)
Two-Year-Old: 24–36 mo. 400 (300–500)
Mature 600
Light Horses and Mules
Foal: 0–6 mo. 190 (80–300)
Weanling: 6–12 mo. 450 (300–600)
Yearling: 12–24 mo. 700 (600–800)
Two-Year-Old: 24–36 mo. 900 (800–1,000)
Mature 1,100
Draft Horses
Foal: 0–6 mo. 360 (120–600)
Weanling: 6–12 mo. 800 (600–1,000)
Yearling: 12–24 mo. 1,150 (1,000–1,3005)
Two-Year-Old: 24–36 mo. 1,450 (1,300–1,600)
Mature 1,800
Calf: 0–1 yr. 525 (50–1,000)
Cow 1,200
Bull 2,000
Fawn: 0–6 mo. 36 (7–65)
Yearling Doe: 6–18 mo. 95 (65–125)
Yearling Buck: 6–18 mo. 110 (65–155)
Mature Doe
Mature Buck
Young: 0–6 mo. 80 (15–145)
Mature Female
Mature Male
Cria: 0–1 yr. 85 (20–150)
Yearling: 1–3 yr. 225 (150–300)
Mature 325

Acres Suitable for Application of Manure

The acreage number used in the animal density calculation is all acres, owned and rented, that are suitable for the application of manure. This acreage is determined to be those lands that meet the following criteria:

  • cropland, hay land, or pastureland (owned or rented) that is an integral part of the operation
  • land that is under the management control of the operator
  • land that is or will be used for the application of manure from the operation

Farmstead and forestland cannot be included in this calculation as land suitable for manure application.

Animal Density

The number of acres that meet the criteria listed above are then divided into the total AEUs on the farm to determine the overall animal density for the operation. Use the blank worksheet on page 4 to calculate the animal density on your farm.

Concentrated Animal Operations Requirements

A CAO as defined under the original regulations that was in existence on the effective date of the revised regulation (October 1, 2006) should already have an approved nutrient management plan. The following are the new plan submission requirements of CAOs as defined in the revised regulations:

  • An existing operation that becomes a CAO due to the changes in the regulations listed above must have submitted a nutrient management plan for approval by October 1, 2008.
  • A new CAO that comes into existence after the effective date must have an approved plan prior to the commencement of manure operations.
  • An agricultural operation that is planning an expansion that will result in that operation becoming a CAO must have an approved plan prior to the expansion.
  • An agricultural operation that because of loss of land suitable for manure application now meets the criteria for a CAO must submit a nutrient management plan within six months after the date of the loss of land.

Example CAO Calculations

The following is an example of an AEU per acre calculation.

Example Farm Data
Animal Inventory (Average weights taken from Table 1) 110 dairy cows @ 1,300-lb average weight each
35 heifers @ 900-lb average weight each
20 calves @ 375-lb average weight each
15,000 heavy broilers @ 3-lb average weight each
Production Period Cows = 365 days per year
Broilers = 5 flocks for 57 days each, or 285 days per year
Land Inventory Farmstead = 5 acres
Woodland = 3 acres
Pasture = 4 acres
Cropland, home farm = 60 acres
Cropland, rented farm = 36 acres
Using this example data and the worksheet, the calculation of animal density (AEUs per acre) for this farm would be as follows:
Animal Type No. Animals × Animal Weight (lbs) × Prod. Days ÷ Factor = AEU
* If this figure is less than 8, then the farm would not be a CAO, regardless of the AEU/acre figure calculated below.
** Includes only cropland, hayland, and pastures; for this example there are 96 acres of cropland/hayland and 4 acres of pasture.
Dairy 110 × 1,300 × 365 ÷ 365,000 = 143.0
Heifers 35 × 900 × 365 ÷ 365,000 = 31.5
Calves 20 × 375 × 365 ÷ 365,000 = 7.5
Broilers 15,000 × 3 × 285 ÷ 365,000 = 35.14

× × ÷ 365,000 =

× × ÷ 365,000 =

× × ÷ 365,000 =

Total* = 217.14

Acres available for manure** ÷ 100

AEUs/acre = 2.17

This example farm would be defined as a CAO and would be required to develop and implement an approved nutrient management plan. The animal density criterion is not to be construed as prohibiting development or expansion of agricultural operations that would exceed the criterion. It simply means that these operations will be required to have an approved nutrient management plan. Farms with an animal density higher than 2 AEUs per acre are likely to have more nutrients than can be fully used by the crops grown on the farm. Thus, nutrient management plans for CAOs often will describe on-farm manure utilization, as well as procedures for moving some manure off the farm.

Use this worksheet to determine if your farm is a CAO:
× Animal Weight
× Prod. Days ÷ Factor = AEU
* If the total AEUs on the farm are less than 8, the farm is not a CAO, regardless of the animal density.
** Farms with an animal density of greater than 2 AEUs/acre are defined as CAOs.

× × ÷ 365,000 =

× ×
÷ 365,000 =

× ×
÷ 365,000 =

× ×
÷ 365,000 =

× × ÷ 365,000 =

× × ÷ 365,000 =

× × ÷ 365,000 =

Total* =

Acres available for manure** ÷

Animal density: AEUs/acre =

Other Required Plans

Farms receiving financial assistance for nutrient management, such as from the Chesapeake Bay Program, are also required to have a nutrient management plan. Any farm that violates the Clean Streams Law also may be required to develop a nutrient management plan.

Voluntary Plans

Farms with fewer than 2 AEUs per acre and farms with fewer than a total of 8 AEUs on the operation are encouraged to voluntarily develop nutrient management plans. Nutrient management plans, whether required or voluntary, can improve farm profits, help protect the environment, provide some protection from liability, and enhance the image with the general public of agriculture as a good steward of our natural resources.

For More Information

For more information, contact your local Penn State Cooperative Extension office or your local conservation district. For a summary of the Nutrient Management Act and regulations, see Penn State’s Nutrient Management Legislation in Pennsylvania: A Summary of the 2006 Regulations, which is available from your local Penn State Cooperative Extension office.

Prepared by Douglas Beegle, distinguished professor of agronomy, and Jerry Martin, senior extension associate, in cooperation with and with funding from the Pennsylvania State Conservation Commission

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Pennsylvania's Nutrient Management Act (Act 38): Who Is Affected?


Agronomy Facts 54





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Contact Information

Douglas Beegle
  • Distinguished Professor of Agronomy
Phone: 814-863-1016