VALUE OF OAK LEAVES FOR FORAGE. 19 



Nitrogen-Free Extract. In oaks the nitrogen-free extract, consisting 

 of starch, sugars, pentosans, etc., does not equal alfalfa in any species, 

 and in Scrub Oak falls as far below as 10 per cent. This fact indicates 

 a lower fattening and heat-producing power than in alfalfa. 



Tannin. Tannin is an astringent principle found in many plants. 

 Aside from its astringent properties, it is acrid, and therefore offensive 

 to the palates of animals. In the stomach, it precipitates the pepsin 

 and peptones, thus preventing the formation of dextrose and hindering 

 digestion. Great thirst and constriction in the digestive tract usually 

 follow an overdose of it. These effects are not so marked in some tan- 

 nins as in others, for some do not have so great a precipitating power as 

 do others. 



In determining the tannins in the oaks, it was found to vary greatly 

 in the different species, but did not serve as an infallible indication of 

 the value of the leaves for forage. For example, Quercus douglasii, which 

 is the poorest forage oak analyzed, is lowest in tannin, while Q. dumosa, 

 a species preferred by sheep and goats, contains 13 per cent, the largest 

 amount of tannin determined in any one species. 



The average of tannin for all the oaks is a little over 10 per cent. In 

 tasting the powdered specimens of the various species, the intensity of 

 acridity perceived coincides with the tannin percentages. In comparison 

 with oak leaves, alfalfa contains an inappreciable amount of tannin. 



Water. Although the water-content of the oak leaves was placed on 

 an alfalfa hay basis, this does not indicate their true comparison when 

 both are green. Green alfalfa contains 80 per cent of water, ^which is 

 from 10 to 20 per cent higher than that in the various species of oaks. 

 This shows the oak leaves to be a somewhat more concentrated feed in 

 regard to protein, ash, and nitrogen-free extract, than appears in the 

 comparison on an alfalfa hay basis. 



Injurious Constituents. Judging from the results of the chemical 

 analyses of these oak leaves, they would seem to occupy a high place 

 among forage plants. This would be the case were it not for excessive 

 amount of three of the chemical constituents; namely, crude fiber, resins 

 and waxes, and tannin. 



The high percentage of crude fiber taken together with the low per- 

 centage of nitrogen-free extract produces a coarser and less nutritious 

 feed than leguminous crops. 



The resins have pungent and disagreeable flavors, which render them 

 distasteful to stock. A good example of this is seen in the Quercus 

 californica, before cited. The leaves of the young trees and shrubs of 

 this species contain no more tannin than those of most of the other 

 species, are only 1-J per cent below alfalfa in nitrogen-free extract, have 

 a fair amount of protein, are low in crude fiber, and are large and soft. 



