STEER DIET COMPOSITION UNDER 3 PERENNIAL GRASS USE INTENSITIES ON RANGELAND IN MENDOZA, ARGENTINA

Botanical composition of steer diet (fecal sampling with microhistolog ical analysis) and availability of grasses and forbs (clipping method) and shrubs and trees (dimension analysis) in pastures stocked at 25, 50 and 80% use of perennial grasses were determined during two 120-day grazing periods under a four-pasture, one-herd grazing system. Diet c omposition was not different (p < 0.01) when grass use was less-than-o r-equal-to 50%. Steers were forced to significantly alter (p < 0.01) d iet selection patterns from the beginning to the end of grazing period s in all treatments by consuming less grasses and more browse. Diet co ntent was closely related to the live herbage available.