TheImprovement ofTropical and Subtropical Rangelands

GRAZING MANAGEMENT 119
the loss of desirable forages can be prevented by manipulation of the
time and intensity of grazing. Grazing may need to be varied within
the growing season in some cases, among sequential growing seasons
in other cases, or in a combination to most effectively match the
livestock with the forage.
Rangeland productivity may decline with grazing unless the
practices that reftect certain principles are followed. One of the main
principles of grazing management concerns the duration of time that
animals are allowed to graze a given area and the timing of this
grazing to critical stages of vegetation growth. A second considers
the degree of uniformity of U8e that plants receive as inftuenced by
an even distribution of grazing animals across a given area. A third
involves the type oflivestock grazed as a means of manipulating plant
communities. The most sensitive, and thus the last, main principle
that should be addressed, particularly on communal grazing lands,
relates to the numbers of animals grazing an area. All of these principles
must be applied to one degree or another when prescribing a
grazing management scheme.
TIME or GRAZING
The primary purpose of range management is to prevent excessive
grazing. This is especially important during the growing season
in order to increase the vigor and productivity ofexisting plants and,
eventually, to improve species composition. An alternative to heavy
grazing to obtain use of less desirable plants is to graze a unit during
that time of year when less desirable species are more palatable
than preferred plants. In South Mrica, it was found that the longer
the period of grazing, the lower the carrying capacity and the more
adverse the effect upon the associated rangelands.
Nutritional quality of forage is highest early in the growing season
and declines as the plants mature. Grasses, forbs, and browse
are similar in quality in the earliest growth stages. As plants mature,
subetantialstructural changes occur that usually decrease palatability
and always reduce nutritional quality. When the seasonal changes
are complete, grasses remain good and are often adequate sources
of energy for ruminants, whereas shrubs (or browse) are deficient in
energy but usually adequate in protein and important vitamins and
minerals (many are deep-rooted legumes). Forbs vary considerably
but tend to be intermediate in nutritional quality, although they are
often unavailable because of weathering and disintegration of leaf