Figure 1-20. An ungrazed 

 stand of Idaho fescue (Fes- 

 tuca idahoensis), a bunch- 

 grass highly relished by cat- 

 tle. (Cf. Figure 1-21.) Note 

 sharp transitions between 

 vegetation types. Northeast- 

 ern CaHfornia. (U. S. Forest 

 Service.) 



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ibility to frost damage. The various biotypes and ecotypes within 

 a grass species usually vary considerably even in the same 

 region, so strains desired for grazing or for mowing can usually 

 be readily developed in breeding programs. 



Each kind of animal has preferences for certain kinds of plants 

 (Figures 1-20 and 1-21). Some feed on a variety of species, others 

 on only a few, or on only one. Sheep as a rule choose broad-leaved 

 herbs (forbs) and the tender parts of grasses, cattle and horses 

 usually prefer grasses, and deer and moose browse on many kinds 

 of shrubs and trees. These preferences are caused partly by the 

 requirements and habits of the animals and partly by the palat- 

 ability or desirability of the plants. Differences in palatability 

 occur between strains of grasses as well as between species, and 

 are caused by variations in succulence, food content (sugar, pro- 

 tein, starch, fat, vitamin A), fiber and ash contents, presence of 

 volatile oils, disease incidence, and stage of maturity. Relative 

 proportion of species in the stand, familiarity of the animal with 



Figure 1-21. Cattle have 

 selected Idaho fescue, re- 

 sulting in the death of many 

 bunches, thus giving oppor- 

 tunity for the invasion of 

 less palatable species. (Cf. 

 Figure 1-20.) Northeastern 

 California. (U. S. Forest 

 Service.) 



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