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The abundance of Lehmann lovegrass (Eragrostis lehmanniana, Nees.) on Arizona ranges prompted this research to evaluate the animal production and winter palatability of this species. Sulfurcoated urea (SCU) was applied to desert grassland range to minimize the risks of fertilization that are brought about by drought and unseasonable rainfall. Tebuthiuron (TEB) was also applied to pasture to document any beneficial effects on forage production and palatability. During the 2 years of this project, two experiments were conducted. A preference study examined forage and animal responses to one-time applications of fertilizer or herbicide treatments and combinations. The second experiment compared the potentials for improved animal production from SCU and SCU + TEB with untreated range. Results indicated that the fertilizer and combination treatments produced more forage than the untreated plots. Tebuthiuron improved forage production by 200 percent in the first year but reduced yields in the second year. The high rate of TEB was detrimental in both years. Forage utilization was improved by all treatments. Nitrogen increased the crude protein content of the grasses proportional to the rate applied. Tebuthiuron also enhanced the protein content of the forage. Total available carbohydrates were lowest in TEB treated forages, but digestibility was increased. Only the 31 lb SCU appeared to be economically profitable. However, excellent carry-over by the 60 SCU treatment suggested profitability after 3 years. Results from the grazing study indicated that production was significantly improved by both treatments. Although forage production was similar for the treatments, the SCU-only pasture provided superior animal gains and greater carrying capacity than the SCU + TEB pasture, even though forage digestibility and apparent disappearance were greater on the combination pasture. The difference in animal performance was attributed to low levels of carbohydrates available from the combination pasture. Treatment of Lehmann lovegrass/blue grama range with 40 SCU/acre appeared profitable for raising growing beef animals, but not for maintenance of a breeding cow herd.

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Two trials were conducted to demonstrate diet selected by grazing cattle. Selection criteria were investigated on the basis of cattle selection for plant species, green leaf in preference to dry leaf or dry stem and the chemical contents of esophageal samples versus those in the standing crop. The influence of residual old vegetation on selection ability was studied by mowing all or part of the pasture. Cattle consumed Lehmann lovegrass in preference to shrubby species (Table 1). The esophageal samples contained higher levels of protein, phosphorus and IVDMD than that in the standing crop in both Trial 1 and Trial 2. Neutral detergent fiber was higher in the standing crop than in the esophageal samples, whereas in Trial 2, there appeared to be no difference in NDF. Removal of old vegetation by mowing had no effect on selection for plant parts. Cattle selected green leaf, in preference to dry leaf or dry stem regardless of the presence of old material. Free ranging cattle selected a diet that was higher in nutrient density and more digestible than the available forage.

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