574 



NUTRITION OF FARM ANIMALS 



As the plant matures, the cell walls grow thicker and be- 

 come more and more impregnated with tough, woody material. 

 At the same time, more soluble carbohydrates, as starch and 

 sugar, are being produced, while the protoplasm comes to oc- 

 cupy but a small part of the cell. The fully mature forage, 

 therefore, is rich in crude fiber of a tough, resistant sort, contains 

 much carbohydrate material in general and tends to be poor in 

 proteins. For example, three samples of meadow-grass, cut 

 at different dates, had the following composition, reduced to a 

 uniform percentage of water : 



TABLE 163. COMPOSITION OF HAY CUT AT DIFFERENT DATES 



Accompanying this change in composition goes a decrease in 

 digestibility. In the first place, the crude fiber becomes more 

 resistant to the action of the digestive organs. Furthermore, 

 the less soluble crude fiber seems to have a tendency to pro- 

 tect the contents of the cells from digestion. At any rate, 

 the percentage digestibility of the protein, and, to a less de- 

 gree, that of the other ingredients also suffers. The percentage 

 digestibility of the several ingredients of the above samples of 

 grass, omitting the ash, was found to be as follows : 



TABLE 164. PERCENTAGE DIGESTIBILITY OF HAY CUT AT DIFFERENT 



DATES 



