Carrying capacity is the number of animals that can graze an area without degradation of the forage resources. This will depend on the number of months grazing will take place and forage production. The degree to which forage resources are grazed is critical. A high degree of use (more than 60% consumption of the available forage) gives maximum returns per acre but can cause deterioration of the forage. A low degree of use (35% or less consumption) maximizes returns per animal but underutilizes the resource. A medium degree of use (40 to 50% of the available forage) gives a good return while causing no harm to the resource. An accepted rule of thumb for grazing is to use half and leave half. This type of grazing management allows the forage to resupply the energy reserves it needs for sustained growth.
Source:
Demers, C. and R. Clausen. (2002). Managing Cattle or Timberlands: Forage Management. University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS).
