SUMMARY

A study was made on the effect of superphosphate fertilizer on digestibility of OM and CP in diets selected by cattle grazing Stylosanthes-native grass pastures during the wet, wet-dry transition and dry seasons. Fertilizer application had significant (P(O.01) effects on intakes of DOM and CP and on faecal CP only during the wet season. There were marked seasonal effects on most parameters with a decline in nutrients consumed throughout the year for both unfertilized and fertilized pastures. DOMI from fertilized pastures would support high levels of production during the wet season and should maintain live weight in the dry. Adequacy of N supply during the dry is not clear; use of relation-ships obtained with sheep fed temperate forages does not clarify the matter. The need to derive predictive relationships for cattle grazing tropical pastures is discussed. Keywords: Stylosanthes, superphosphate, nutritive value, cattle