- It is “the proportion of Current year’s production that is consumed or destroyed by grazing animals.” _ SRM 1974
- “The degree to which animals have consumed the usable forage production expressed in percentage.” _ Stoddart et al 1975
- The concept may be applied to:
- Single plant
- Single Forage spp
- Group Forage spp
- Range Forage as a whole
Methods of Calculation of Range Utilization:
- Clipping before and after grazing:
- Cage comparison method
- Stem count method
- Height-weight method
- Length of twig or twig length method
Clipping before and after grazing:
Two (paired) plots are selected uniformly distributed on the range area that is to be grazed. Of the each paired plots, one is clipped before grazing and the other clipped after grazing. Average wt of plots before and after the grazing is calculated; then
Eg weight before grazing = 98 gm/m2
After four months grazing, weight (wt)= 38 gm/m2
% Utilization = 98-38/ 98 * 100
% Utilization = 61.22%
Cage comparison method
This is the most common methods of estimation of leaves determining rang utilization, especially during the grazing season. The paired plats are located/ selected randomly and are uniformly disturbed over the range area. One plot is caged and the other is left open to grazing. The animals are allocated to graze. At the end of grazing season, the forage wt from protected/ fenced as well as from unprotected plot is obtained by clipping each of them separately. The average weight of clipped material from unfenced plots = 17 gm/ m2
% Utilization = 52 – 17/ 52 * 100 -> 3400/ 53 = 67.31%
Stem count method
This method involves simple enumeration ie count the no of shoots grazed or un-grazed for individual spp. Eg 30 plants were counted. The average is worked individually.
In the past, it was assumed that a direct relationship exists b/w the amount of height removed and the amount of wt removed. If the height of forage spp removed was 50%, then the utilization was considered as 50%.
Length of twig or twig length method
This method is generally applied for the calculation of utilization of browse spp. The length of several twigs on many branches within the reach of grazing animals of different shrubs/ trees is measured. The measured twigs are tagged and the same twigs are re-measured at the end of razing period. The reduction in the twig length is the length grazed by animals.
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