i] Introduction 3 
especially true of sheep. We have often observed sheep eating greedily 
on one day plants which they could scarcely be persuaded to eat on the 
following day on the same range." In the case of one flock of sheep on a 
foothill range at an altitude of 4,600 ft. "a few of the sheep were observed 
eating large quantities of wild sunflower (Balsamorhiza sagittata), a few 
ate freely of false lupine (Thermopsis rhombifolia), some confined their 
attention largely to the wild geranium, while others ate false- esparcet 
(Astragalus bisulcatus) almost exclusively. Two sheep were seen eating 
the leaves of lupine, and about fifty ate a greater or less quantity of 
Zygadenus venenosus, while the majority of sheep in the band fed 
exclusively upon the native grasses on the range." 
Horses also have been known to acquire in America a depraved 
appetite for horsetail and loco-weed. 
The different species of live stock are often quite differently affected 
by poisonous plants, some being very susceptible to a given plant while 
others may be little or not at all susceptible. One species (e.g. the pig) 
may readily vomit the poison of a plant which is emetic, while another 
(e.g. the horse) may be unable to do so and hence be the more seriously 
injured. The variability of the different classes of live stock in this 
respect is frequently brought out in Chapters n to vi. Poisonous 
effects may also vary with the individuality and age of animals of the 
same species. 
At certain periods of the year e.g. in early spring, and during dry 
summers, there may be a scarcity of green herbage, and this may 
induce animals to eat any green plants which are especially early, 
including poisonous ones, which they would otherwise refuse. 
In some cases poisonous plants which do not lose their toxic pro- 
perties on drying (e.g. meadow saffron) may be included in hay, and 
hence find their way to stock in such a form that they may not be dis- 
tinguished. It has been found, however, that some poisonous plants 
or parts of them are refused by stock when mixed with good herbage 
in hay. Care should be exercised that poisonous plants are not included 
with hay or green fodder, and in cases of poisoning all forage should be 
examined. 
Animals may also be poisoned by certain toxic seeds (e.g. corn 
cockle) fed to them with cereal grains, in feeding stuffs generally, or in 
the refuse seeds from the sources mentioned. Here again judgment 
is necessary, and it is probably advisable on all counts to burn the 
weed seeds and similar refuse from the sources mentioned. Poisonous 
seeds may occur in low quality feeding stuffs, and poisonous seeds of 
12 
