Study details: Excel spreadsheet
 
 

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By Katharine Knowlton, Ph.D.
Assistant Professor, Virginia Tech

In response to environmental concerns, local, state, and federal regulations area becoming increasingly strict, and large farms are often required to obtain permits. Permits typically require manure storage sufficient to prevent manure application to frozen ground, containment of all potential runoff, regular inspections, and implementation of a nutrient management plan to match manure application to crop nutrient needs (typically nitrogen). The goal of these permits is to keep nutrients on the farm, and prevent contamination of water supplies with nutrients, sediment, and pathogens.

Most states determine which operations must obtain permits by the number of animal units on the farm. An animal unit is the equivalent of 1,000 lbs. of live weight, so a 1,400-lb. cow generally equals 1.4 animal units. Some states require permits for operations with more than 300 animal units (approximately 200, 1,400-lb. cows), while others require operations with over 1,000 animal units (around 700, 1,400-lb. cows) to obtain permits.

There are several questions being raised by farmers nearing these limits. First, is animal numbers really the best way to determine who needs a permit? While larger farms certainly generate more manure, quantity of manure is not an environmental issue—nutrient loss is. Also, there is variation in how these animal numbers are counted. Some states count all animals on the farm, others count only lactating cows.

An interesting question is increasingly being raised by Jersey farmers across the country. A Jersey cow typically weighs 900 to 1,000 lbs.—not 1,400 lbs.—so if permit requirements are set by animal units, Jerseys should count as 1 animal unit, not the 1.4 typically used. By this logic, it takes 300 Jerseys, not 200, to equal 300 animal units. Reinforcing this is a body of research data indicating the obvious: Jerseys do not produce as much manure on a daily basis as Holsteins, and they excrete less nitrogen per cow per day (Table 1, below).

Jerseys and Holsteins metabolize nutrients similarly, so excretion of feces, urine, and nitrogen per unit of body weight and per unit of feed intake is similar. Total nitrogen excretion per cow per day, however, is significantly less for Jerseys than for Holsteins. This research data indicates that a Holstein is equivalent to 1.4 Jerseys in terms of nitrogen excretion. This difference should allow more Jerseys than Holsteins to be maintained on the same size farm.

Regulators don’t always recognize this difference, however. In Virginia, at least, state agencies are requiring permits for farms with more than 200 lactating cows, regardless of breed.

Jerseys

Holsteins