44 CIRCULAR 925, U. S. DEPARTMENT OF AGRICULTURE 
In contrast, sheep in heavily grazed pasture failed to gain. These 
results are quite similar to those already reported for other sheep in the 
pastures. Ewes that were on moderately or lightly grazed range for 
two or more of the winter periods gained two to three times as much as 
those on heavily grazed range for two or more periods. Sheep that 
remained vigorous and in good condition through one period of heavy 
grazing frequently gained rapidly the following period if they were 
placed on moderately or lightly grazed range. An example of this is 
pair No. 6 of the set that were on moderately grazed range for two or 
more periods. The pair was on moderately grazed pasture in early 
winter, on heavily grazed pasture in the middle winter period, and on 
moderately grazed pasture again in late winter. Although the pair 
lost an average of nearly 2 pounds during the middle period, it made 
an average gain of 9 pounds during the late period. 
Sheep under moderate grazing often gained more than those in the 
lightly grazed range pastures. This may be partly because herbage 
production and plant composition in the various pastures differed, and 
partly because the sheep in smaller groups using the lightly grazed 
areas were more restless and discontented than the larger groups of 
sheep in other range pastures. 
SHEEP PRODUCTION ON RANGE ALLOTMENTS 
To compare differences in production between sheep on moderately 
and heavily grazed winter range, two large experimental allotments 
were selected and two full-sized winter herds of 2,500 to 3,000 sheep, 
essentially similar with respect to breeding history and range opera- 
tions, were used. 
In 1935 the two experimental allotments were typical of neighboring 
winter rangelands with respect to topography, vegetation, and range ~ 
conditions. Both of the allotments or range areas extended from the 
valley bottoms to the mountains. For the most part, they had been 
heavily grazed in previous years and were classed as in poor condition. 
One of these was located on the Desert Experimental Range and the 
other was on a similar adjacent range. 
The allotment within the experimental range was moderately stocked 
at an average rate of approximately 15 sheep-days per acre during the 
period of the study, 1935 to 1947. The rates varied from about 27 
sheep-days per acre in the most productive winterfat and black sage- 
brush subtype to as low as 5 sheep-days per acre on the poorer sites in 
the shadscale subtypes. The rate of stocking also varied from year to 
year with herbage production. 
Ordinarily the herd was placed on the moderately grazed experimental 
allotment in early November as soon as it reached the winter range and 
remained until late April. In years when forage yields were low the 
sheep did not enter the moderately grazed experimental allotment until 
late November or early December. The number of sheep-days feed 
available each year was approximated on the basis of the changes in 
herbage yields that were recorded in October in the range pastures, 
and the dates of entry were varied accordingly. 
Utilization was fairly uniform from year to year. However, from 
the time the herd reached the winter range in early November until it 
entered the moderately grazed allotment, adequate forage was available 
on other parts of the general winter range. During 1935 and 1936 
