TABLE 2.--A summary of the minimum toxic and maximum non-toxic doses of insecticides 
administered orally to livestock at Kerrville, Tex.--Continued 
Maximum Minimum 
Chemical non-toxic toxic dose 
dose tested found 
ORGANIC PHOSPHORUS COMPOUNDS--Continued 
Mg. /kg Mg. /kg 
Bayer 21/199 (Co-Ral) Cattle adult 25 50 
Sheep adult aS) 25 
Ronnel (Trolene) Calves 1-2 weeks 100 125 
Cattle adult 100 125 
Sheep adult 400 250 
4-tert-butyl-2-chlorophenyl Calves 1-2 weeks 25 50 
methyl methylphosphoramidate Sheep adult 150 200 
( Ruelene) Goats adult 150 200 
Horses adult 25 50 
Bayer 17,147 (Guthion) Calves 1-2 weeks Osa oO 
Sheep adult 1255 25 
Delnav Calves 1-2 weeks --- 5 
Diazinon Calves 1-2 weeks 0.5 aba{0) 
Cattle adult 10 2» 
Sheep adult 20 30 
Malathion Calves 1-2 weeks 10 20 
Cattle adult 50 100 
Sheep adult 50 100 
oils or organic solvents were not desirable, because of the possibility of increased ab- 
sorption, or the messiness which follows the oiling of an animal's hair. Three basic 
types of formulations were developed for marketing to livestock owners; dusts, wettable 
(suspensible) powders, and emulsifiable concentrates. 
Dusts have offered fewer problems than the others, but have had limited usage because 
they were, in general, not retained by the treated animals as long as spray deposits. 
Nevertheless, they have had success in treating poultry, sheep, and to some degree other 
animals, particularly when treatments were required in cold weather. 
Dusts are less likely to be absorbed by treated animals, concentration for concentra- 
tion, than emulsions or wettable powders. This advantage is generally lost because of the 
greater concentration required for insect control (82). 
Wettable or suspensible powders have given trouble, usually because their specific 
gravity is relatively high, allowing the particles todrop rapidly to the bottom of containers. 
This has a protectant effect ifthe powders are used in dipping vats (baths) since the effect 
is to decrease the concentration of the supernatant fluid--undesirable from the standpoint 
of parasite control. When used in spraying devices, the settling can be extremely dan- 
gerous, depending upon the mechanical design of the equipment. Without adequate agitation, 
and with the outlet of the tankat the bottom, the concentration inthe fluidis first increased, 
dangerous to animals, then decreased, reducing parasite control. The reverse is true 
with suction applied from the top of the tank downward. 
We also learned that the use of ‘‘stickers'’(chemicals causing insecticides to adhere 
to treated surfaces) and suspending agents could significantly increase the amounts of 
141 
