Cracking the Code on Grazing Management Terminology: Animal Units, AUMs, & How to Apply Them

mixed beef cattle grazing green grass
Does it feel like grazing management information is shrouded in acronyms and terms that boggle the mind on first glance? Do you struggle to decipher terms like animal unit equivalents? And how does one go about calculating AUMs and then applying those numbers? Be reassured, you’re not alone! There’s a lot going on when sorting through the finer points of grazing management and figuring out how to work through the many calculations.

A good starting point is defining a grazing animal in terms of how much forage it requires to meet its nutritional demands. We know that grazing animals’ forage needs differ depending on class, weight, age and stage of production. And in order to account for those differences, it’s helpful to create a baseline in order to quantify forage demand. Continue reading

Two Methods, Four Steps for Calculating Carrying Capacity

Carrying capacity, also known as grazing capacity, is the amount of forage available for grazing animals in a specific pasture or field. Calculating the correct carrying capacity will help you determine a proper stocking rate that maintains productivity of both your animals and forage while encouraging the sustained health of the grassland resources.

Stocking rate is the number of animals on a pasture for a specified time period and is usually expressed in Animal Unit Months (AUMs) per unit area.

One way to determine carrying capacity is to obtain past stocking rates and grazing management information and assess the condition of the pasture. But what if the historical stocking rate data is not available or you are unsure of its accuracy and reliability?

Carrying capacity can be calculated using several different techniques. All of them depend on some trial and error as they are monitored and adjusted over time. When calculating carrying capacity, it boils down to three questions:

  1. How much forage is available?
  2. How much of that forage can be used by grazing animals?
  3. How many animals can graze on that piece of land and for how long?

BCRC Carrying Capacity Calculator
The BCRC Carrying Capacity Calculator provides a road map for answering these questions using two separate methods: 1) forage estimates based on provincial guides and 2) field-based sampling, also known as the clip and weigh method. Each method contains four steps. Continue reading