Canopy Characteristics, Ingestive Behaviour and Herbage Intake in Cultivated Tropical Grasslands

Compared to temperate systems, there have been few detailed assessments of canopy characteristics and associated grazing behavior in planted tropical grasslands. Reasons include the large number of forage species used in warm climates, the diversity of their morphology, research priorities emphasizing germplasm evaluation and management, and limited resources. This review describes canopy attributes of C4 grass pastures, highlights the most important relationships between grazing behavior and these canopy characteristics, and discusses the implications of canopy characteristics and grazing behavior for long-term intake and animal performance. It is suggested that the largest differences in canopy characteristics between tropical and temperate swards are not total canopy measures but those of the upper canopy strata including leaf proportion and bulk density. This occurs because tropical swards, unlike many temperate ones, have large vertical heterogeneity in density, plant-part proportion and nutritive value. In temperate swards, bite weight is primarily a function of sward height, but leaf percentage, leaf mass, or green herbage mass of the upper strata of the canopy usually are more important with C4 grasses. The manner in which leaf is presented to the animal and the degree to which it can be prehended separate from stem and dead material of low digestibility are also of great significance in pastures based on C4 grasses.