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 



Bays. 

 12 

 18 

 33 

 26 



Pounds. 

 36. 641 

 36. 818 

 47. 469 

 55. 844 



Pounds. 

 3.053 

 2.045 

 1.438 

 2.148 



Very sick. 

 Do. 



412 





423 





Do. 



4lx . 





Do. 











22.25 



44. 190 



2.171 







July 6 to Aug. 8 





Group 2: 



Sheep 410 



19 

 20 



18 



38. 443 

 28. 894 

 27. 099 



2.023 

 1.445 

 1.505 



Do. 



419 



July 8 to Aug. 8 



Died. 



420.. 



July 8 to Aug. 9 



Sick. 











19 



31. 479 



1.657 







July 27 to Sept. 16 





Group 3: 



Sheep 448 



17 

 13 

 19 



69. 997 

 25. 368 

 43. 281 



1.489 

 1.951 

 2.278 



Symptoms. 



437 







421 



Aug. 27 to Sept. 18 



Do. 











26 



46.209 



1.902 













