54 FEEDS AND FEEDING 



Adding nitrogenous feeds to roughages, such as hay, straw, etc., does 

 not increase the digestibility of the roughage. Neither does the addition 

 of fat to a ration increase the digestibility of the other constituents. 

 It has been found 14 that feeding fat in excess of 1 Ib. per 1,000 Ibs. live 

 weight or feeding pure fat or oil in unemulsified form may cause digest- 

 ive disturbance. Salt does not affect digestion, tho it may cause animals 

 to eat more food and may improve nutrition. 



The addition of dilute acids, such as sulphuric acid or lactic acid (the 

 chief acid in sour milk and in silage), does not influence digestibility. 

 This is important because silage contains considerable free acid. 



85. Class of animal, age, and breed. Ruminants the ox, cow, sheep 

 digest the same kind of forage about equally well. Kellner, 15 however, 

 showed 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 ascribed this 

 difference to the fact that the contents of the last part of the intestine of 

 the ox remain more watery and hence are subject to more complete fer- 

 mentation. The more easily digested a feeding stuff is, the less difference 

 will there be in its digestion by these various animals. For the great 

 majority of feeding stuffs the same digestion coefficients may be used for 

 the sheep and ox. 



The horse and pig digest less fiber than the ruminant, in whose paunch 

 the coarse feeds undergo special preparation and digestion. The richer 

 the feed, the more nearly do the digestive powers of the horse approach 

 those of other farm animals. Swine digest the concentrates fully as well 

 as do the ruminants, but make only small use of the fiber. 



In general, age does not, in itself, influence digestibility, tho 

 young farm animals cannot utilize much roughage until their digestive 

 tracts are developed. It is shown in later chapters that growing pigs 

 chew corn more thoroly until they reach a weight of about 150 Ibs. 

 and calves masticate grain more completely up to an age of 6 to 8 months 

 than they do later, facts which should be considered in determining 

 whether to grind their feed. 



The digestion of old animals is often indirectly impaired by poor 

 teeth, which make the proper mastication of their food impossible. Breed 

 has no influence upon digestibility. Individual animals may, however, 

 show considerable difference in their ability to digest the same ration, 

 tho ordinarily the digestibility of a given ration by different animals of 

 the same race will not vary by more than 3 to 4 per ct. 



86. Summary. The foregoing discussions make it evident that average 

 figures for the composition of any feeding stuff are but approximately 

 correct when applied to a particular lot of the feed. This likewise ap- 

 plies to the expression of its nutritive value, whether stated in terms of 

 digestible nutrients or net energy. In other words, different lots of any 

 feeding stuff vary in feeding value, the same as different samples of coal 



"Ernahr. landw. Nutztiere, 1907, p. 51. 

 15 Land. Vers. Stat, 63, 1906, p. 313. 



