INCREASING FORAGE YIELDS ON INTERMOUNTAIN WINTER RANGES 49 
TasBLe 13.—Average fall and spring weights and change in body weight 
by age classes of 119 ewes in two herds (A and B) wintered alternately 
at moderate and heavy grazing intensities, 1937—L4 
Moderate grazing Heavy grazing 
Age class 
Fall Spring | Change in Fall Spring | Change in 
weight weight weight weight weight weight 
Pounds Pounds Pounds Pounds Pounds Pounds 
Under | year 23 83.4 Pet 73.0 (821 5.1 
1-year-olds___ 105.6 114.4 8.8 111.8 113.1 33 
2-year-olds___ 118.3 128 .2 9.9 118.4 118.6 0.2 
3-year-olds___ 120.9 130.8 9.9 123.8 124.5 ath 
4-year-olds___ 127.6 135.8 8.2 125.9 126.8 a) 
5-year-olds___ 126.1 D583) 9.2 126.3 126.4 ma 
6-year-olds 
and over_-.- 124.2 132.3 Sou 125.0 124.5 —.5 
During the unfavorable winters of 1937-38 and 1942-43, ewes on 
heavily grazed range suffered losses of as much as 20 to 25 pounds in 
body weight. These drastic losses often left the animals so weak that 
many were unable to survive the long trailing and trucking necessary 
to return them to the spring shearing and lambing ranges. 
WOOL YIELDS 
Fleece weights of all sheep that wintered on the experimental allot- 
ments were obtained after spring shearing from 1936 to 1943. The 
averages for herds under the two treatments are shown in table 14. 
Weights given are on the ‘grease’ or ‘‘dirt”’ basis before the fleeces 
were washed. 
Average fleece weights were greater in every year for the herds that 
grazed at a moderate level. The difference varied from a low of 0.24 
pound per head after the winter of 1935-36 to a high of 1.67 pounds 
after the winter of 1936-37, and averaged 0.95 pound for the period 
of observation. 
The greater fleece weight of the sheep on the moderately grazed 
areas is attributable to the larger amounts of nutritious forage they 
consumed. A previous study in New Mexico has presented evidence 
that the plane of nutrition has a marked influence on wool yields, and 
that well-fed sheep produce more wool than underfed ones (22). 
DEATH LOSSES 
Observations on winter death losses were made on herds A and B 
during the period of study. Death losses among the sheep on the 
moderately grazed range averaged 3.1 percent, of which about 2 percent 
were killed by coyotes and the remainder died from unknown causes. 
Death losses of sheep on heavily grazed range were more than double 
with an average of 8.1 percent, of which a little more than half was 
due to causes incident to malnutrition and the rest to coyotes and 
