For a number of years many tons of sprayed or dusted hay have been fed successfully to livestock by stockmen interested in controlling the alfalfa weevil; nevertheless. the supposed cases of poisoning that have been reported naturally have caused concern among feeders.
Further confusion on this question has resulted from reports on studies designed to determine the effect of lead arsenate instead of calcium arsenate.
Whether the lead in lead arsenate has been a more injurious agent than the arsenic, of course, is difficult to state. Most of the experiments performed in the feeding of sprayed or dusted hay have been conducted with small experiment animals, as guinea pigs, rats, and rabbits.
Despite the proven effectiveness of calcium arsenate in alfalfa weevil control, a number of stockmen are still doubtful as to the feeding value of hay from alfalfa thus treated, fearing it might be poisonous to livestock. As a rule, their fears in this respect are traceable to reports of poisoning based upon fallacious reports from different sources. Direct information on this subject is limited and difficult to obtain; especially is this true with calcium arsenate. In order to get direct information on the feeding value of alfalfa hay treated with calcium arsenate the study constituting the basis of this bulletin was undertaken.
Frederick, H. J., "Bulletin No. 223 - Feeding Value of Alfalfa Hay Treated with Calcium Arsenate" (1930). UAES Bulletins. Paper 186.