Heifer Performance Under Two Stocking Rates on Fourwing Saltbush-Dominated Rangeland

The efficiency of livestock production in shortgrass steppe may be increased by grazing fourwing saltbush (Atriplex canescens [Pursh] Nutt)-dominated rangeland in late fall and/or early spring, but there is a paucity of information concerning stocking rates and animal gains. The objective of this study was to compare the effects of light and moderate stocking rates on weight gains of heifers grazing twice-replicated 16-ha pastures in late fall (November to mid-January) from 1996 to 1998, and in early spring (April to mid-May) from 1996 to 1999. Stocking rates for late fall (light: 1.3-1.5 ha animal unit month-1 [AUM-1] vs. moderate: 0.8-1.0 ha AUM-1) and early spring (light: 3.7-4.0 ha AUM-1 vs. moderate: 2.3-2.5 ha AUM-1) were achieved using 5 (for light grazing) and 8 (for moderate grazing) Hereford heifers, with initial average weights of 405 +/- 5.7 (mean +/- 1 SE) kg for the late fall grazing period and 267 +/- 3.8 kg for the early spring grazing period across the study years. Average daily gain was 58% greater for light (0.65 +/- 0.06 kg head-1 d-1) compared to moderate (0.41 +/- 0.05 kg head-1 d-1) stocking rates in the late fall grazing period, and 115% greater with light (0.59 +/- 0.06 kg head-1 d-1) than with moderate (0.27 +/- 0.07 kg head-1 d-1) stocking rates in the early spring grazing period. Beef production did not differ between stocking rates for either the late fall (16.4 +/- 3.9 vs. 17.4 +/- 4.5 kg gain ha-1, light vs. moderate stocking rates) or early spring (9.6 +/- 2.7 vs. 7.6 +/- 4.8 kg gain ha-1) grazing periods. We suggest that land managers employ light stocking rates during both grazing periods to obtain adequate individual animal gains without sacrificing gains per unit land area. Lengthening the grazing season in the shortgrass steppe should be economically desirable to land managers because feed costs could be lowered and animal gains obtained through minimal input.