Act 38 of 2005, known more commonly as the Nutrient Management Act, was put in place to regulate livestock and poultry operations, including horses, known as Concentrated Animal Operations (CAOs). A CAO is any operation with at least 8,000 pounds of total animal weight, and 2,000 or more pounds of animals per acre, or 2 AUs per acre (an AU, or animal unit, is equal to 1,000 pounds. For example � a 1,000 pound horse would be equivalent to 1 AU.) A farm that is considered a CAO is required to have an approved Nutrient Management Plan developed by a certified Act 38 plan writer. A Nutrient Management Plan determines how much manure, and other sources of nutrients, can be applied to the land. The goal is to keep Nitrogen and Phosphorus at manageable and environmentally safe levels. All livestock operations are encouraged to have a Nutrient Management Plan, even if they are not CAOs. Operations that are not considered CAOs, but have an approved Nutrient Management Plan are known as Volunteer Operations. Below is a link to the Penn State Nutrient Management website, which explains the program in much more detail.