36 
BULLETIN 947, U. S. DEPARTMENT OF AGRICULTURE. 
The results show that an average daily feeding of dry leaves of 
2.116 pounds continued for 16.5 days produces sickness. On page 33 
it is shown that an average daily feeding of 2.228 pounds of green 
leaves produces sickness if continued for 21.58 days. Judging by 
these figures alone it would appear that the dry plant is more toxic 
than the green. After making allowances for the small number of 
cases and the necessary inaccuracies of the detail of the experiment, 
it seems probable that there is no material difference in toxicity 
between the green and dried plant. It should be noted in this con- 
nection, however, that the dry plant used in the experiments had 
been collected and dried under cover and that this conclusion might 
not apply to the plant dried standing on the range. 
SEASONAL VARIATION IN TOXICITY OF THE PLANT. 
For practical purposes it is desirable to know whether the plant is 
especially toxic at any particular season. Part of the experiments 
of 1917 and 1918 can readily be divided into two groups, one occur- 
ring in June and early July, and the other in late July, August, and 
September. 
In June, 1917, Sheep 424, 415, 413, 432, and 428 were given single 
forced feedings with an average dose of 2.358 pounds, three being 
made sick and two dying. Sheep 444, on September 13, showed 
symptoms from a forced feeding of 2.217 pounds. The difference 
between the two groups evidently is very slight. 
The sheep receiving prolonged feedings of leaves in 1917 can be 
divided into three chronological groups, as shown in Table 13. 
Table 13. — Seasonal variation in toxicity of plant. 
Animal. 
Date of feeding. 
Days 
to pro- 
duce 
sick- 
ness. 
Quantity per hun- 
dredweight of 
animal to pro- 
duce sickness. 
Result. 
Total. 
Daily 
average. 
Group 1: 
Sheep 411 
1917. 
June 8 to 23 
Days. 
12 
18 
33 
26 
Pounds. 
36.641 
36. 818 
47. 469 
55. 844 
Pounds. 
3.053 
2.045 
1.438 
2.148 
Very sick. 
412 
June 8 to July 6 
Do. 
423 
June 8 to July 13 
Do. 
418 
Do. 
22. 25 44. 190 
2.171 
July 6 to Aug. 8 
Group 2: 
Sheep 416 
1 
19 ! 38. 443 
20 28. 894 
2.023 
1.445 
1.505 
Do. 
419 
July 8 to Aug. 8 
Died. 
420 . 
July 8 to Aug. 9 
18 
27.099 
Sick. 
19 
31. 479 
1.657 
July 27 to Sept. 16 
Group 3: 
Sheep 448. . 
47 
13 
19 
69.997 
25. 368 
43. 281 
1.489 
L951 
2.278 
Symptoms. 
437 
Aug. 21 to Sept. 8 
Very sick. 
421.. 
Aug. 27 to Sept. 18 
Do. 
26 
46.209 
1.902 
