42 Feeds and Feeding. 



lowers the digestibility of the crude protein. At the Oregon Sta- 

 tion^ Withycombe and Bradley found that steaming both vetch 

 and corn silage materially decreased the digestibility of the crude 

 protein and other nutrients. In general, cooking, steaming, or fer- 

 menting food, while often improving its palatability, generally 

 lowers its digestibility, tho potatoes and possibly other starchy 

 tubers are improved thereby. 



When nitrogenous feeds, such as oil meal, oats, etc., are added to 

 roughages — hay, straw, etc. — the digestibility of the roughage is not 

 thereby increased. The addition of a large quantity of digestible 

 carbohydrates, such as sugar and starch, to a ration containing 

 much roughage may reduce the digestibility of its crude protein 

 and fiber. If pure carbohydrates, such as starch and sugar, form 

 more than 10 per ct., or roots and potatoes furnish more than 15 per 

 ct., of the dry matter in the ration, its digestibility is diminished 

 thereby. At the Weende Station, in a trial with sheep, the addition 

 of 0.5 lb. of starch to a ration containing 1.75 lbs. of hay reduced 

 the digestibility of the crude protein from 54 per ct, to 32 per ct. 

 and of the fiber from 60 per ct. to 54 per ct. This depression does 

 not occur when nitrogenous feeds, such as oil meal, supplement the 

 starch or sugar. Adding fat to a ration does not increase the diges- 

 tibility of the other constituents. Salt does not affect digestion, 

 tho it may increase the quantity of food eaten and improve nutri- 

 tion. 



If green forage is cured without waste and in a manner to pre- 

 vent fermentation, the mere drying does not lower its digestibility. 

 Ordinarily, however, in curing forage much of the finer and more 

 nutritious parts is wasted, and dews, rain, and fermentations effect 

 changes which lower digestibility. The large amount of work done 

 in masticating dry forage and passing it thru the alimentary tract 

 explains why green forage may give better results and hence ap- 

 pears more digestible than dry forage. The long storage of fod- 

 ders, even under favorable conditions, decreases both their diges- 

 tibility and palatability. Hay browned by heating shows increased 

 digestibility of fiber but decreased digestibility of crude protein and 

 carbohydrates. 



Ruminants — the ox, cow, sheep — digest the same kind of forage 

 about equally well. Kellner,- however, shows that the ox is able to 

 digest as much as 11 per ct. more of the less digestible roughages, 

 such as straw, than is the sheep. He ascribes tbis difference to the 



* Bui. 102. = Land. Vers. Stat., 63, 1906, p. 313. 



