STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 37 



Important range plants and the vegetation as a whole were con- 

 siderably affected by heavy stocking with sheep for 6 years, as com- 

 pared with conservative and light stocking. Recovery of vegetation 

 from drought levels was retarded, and there was much less increase in 

 total vegetation density. Although blue grama plants were more 

 numerous, they were smaller in size at the close of the experiment. 

 Both the number and size of needle-and-thread plants were decreased. 

 Bluestem wheatgrass also became less abundant, and showed reduced 

 height growth. Low-value annuals, on the other hand, increased 

 manyfold. 



Because of the high proportion of annuals growing in the heavily 

 stocked pasture in 1942, the total production per acre of range herbage, 

 clipped to a centimeter stubble, was actually larger than in other 

 pastures. This was not a real advantage, however, since at best 

 annual plants are low in palatability and cannot be depended upon 

 to provide forage for several months each year. The dependable 

 perennial species, mostly grasses, produced considerably more herbage 

 on the conservatively and lightly stocked range. Converted to usable 

 forage by applying the percentage of utilization resulting from con- 

 servative stocking, production still favored conservative over heavy 

 stocking. The comparative weights of annual- and perennial-type 

 herbage plus the greater number of annual plants present at the close 

 of the experiment indicate that 6 years of heavy stocking with sheep 

 caused the composition of the range vegetation to shift from a pre- 

 dominance of perennials to a predominance of low-value annual spe- 

 cies. Some movement of topsoil, particularly on the slopes, occurred 

 under heavy stocking. 



On heavily stocked range, the yearling ewes gained significantly 

 less weight during the average grazing season than those on conserva- 

 tively and lightly stocked range. Average seasonal gains over a 

 5-year period were 31, 32, and 33 pounds, respectively. Up to mid- 

 summer, the difference in gain between lots on differently stocked 

 range was hardly noticeable, but throughout late summer and fall 

 the ewes on heavily stocked range lagged badly in weight gains. 

 Starting weights ranged from 70 to 77 pounds and final weights from 

 101 to 109 pounds on the average. 



A minimum of 0.67 surface acre of range, similar to the experi- 

 mental range, per month or 5.4 acres for an 8-month season begin- 

 ning in March is recommended for normal development and main- 

 tenance of a dry yearling ewe. This rate of stocking will also allow 

 some improvement in the range vegetation and provide for a desirable 

 carry-over of unused forage at tin 4 end of each grazing season. Utiliza- 

 tion of the range should be gaged by the percentage of plants grazed 

 and average stubble heights to which certain key species are taken 

 by sheep. Sheep range similar to that studied should be considered 

 properly used when the three key species, blue grama, bluestem, and 

 threadleaf sedge, are grazed rather uniformly over tin 1 range in accord- 

 ance with the utilization guides given in this publication. The 

 guides include a measure of safety against a low forage 'Top during 

 drought and do not take into account possible regrowth of herbage 

 after grazing. 



In addition to conservative stocking and uniform, proper utiliza- 

 tion of key forage species, use of the range in accordance with a 

 seasonal plan lends stability to range-livestock operations and aid- 

 in minimizing the risks due to drought. 



