Response of cattle to cured reproductive stems in a caespitose grass.

Abstract

Accumulation of wolf plants in rangeland pastures frequently results in waste or incomplete utilization of high quality forage by cattle. The objective of this research was to establish the degree of sensitivity of cattle to cured stems in crested wheatgrass (Agropyron desertorum (Fischer ex Link) Schultes) at 3 stages of phenology (late-boot, anthesis, and quiescence). This was accomplished by providing individual plants having densities of 0, 3, 6, 9, or 12 cured stems per dm2 basal area and measuring frequency and degree of utilization after exposure to cattle grazing. Project design was a split-plot in a randomized complete block with 3 replications, 3 stages of phenology as whole plots, and 5 densities of stems as treatments. A significant (P<0.01) phenology X treatment interaction occurred with cattle being equally sensitive to all treatments containing stems at late-boot and anthesis and oblivious to their presence at quiescence. At late-boot and anthesis stages of phenology 75% of plants with no stems were grazed while only 45% of plants with stems were grazed. Respective levels of utilization from the same treatments were 25 and 8%. A negative response was exhibited by cattle during anthesis when as little as 4% of biomass was contributed by cured stems. These results suggest that old growth stems should be removed or their presence noted as a covariate when conducting palatability studies or when observing plant-specific responses to defoliation by cattle. Cattle were not sensitive to treatments at quiescence when roughly 75% of plants in all treatments were defoliated with 25% herbage removal. This suggests that heavy grazing of a pasture with an objective of obtaining utilization of wolf plants would be most successful after all forage has cured, and cattle are less selective.