Defoliation of Flourensia cernua (tarbush) with high-density mixed-species stocking

• High-density mixed-species stocking resulted in heavy tarbush defoliation (∼75%).
• High tarbush use occurred during short periods (∼9 days) without adverse effects.
• Use of individual tarbush plants by livestock was highly variable (0–99%).

Interest in shrub use by livestock is increasing along with the rising demands placed on rangelands worldwide. Historically, Flourensia cernua (tarbush) has increased in the Chihuahuan Desert but receives limited use by cattle. Cattle, sheep and goats co-grazed eight 0.6 ha tarbush-dominated paddocks during two periods for up to nine days during two consecutive years. Cumulative tarbush defoliation across periods and years averaged 75.6%, with a mean increase of 9.3%/day (P < 0.0001). Defoliation of individual shrubs varied from 5 to 99% in 1989 and 0–100% in 1990, indicating highly variable palatability among individual plants. Sheep lost 2.3–5.5 kg/hd (P < 0.0001) across periods and years when forced to browse tarbush. In 1989, goats gained (P = 0.0345) 0.6 kg/hd in period 1, but the gain in period 2 was not significant (P = 0.2934). During 1990, goats lost 3.1 kg/hd (P = 0.0001) across periods. High-density mixed-species stocking of small areas for short time periods resulted in extensive tarbush use, primarily due to browsing by sheep and goats. Targeted use of tarbush for short time intervals may increase use of this highly nutritious forage and potentially serve as a form of biocontrol for this shrub.