16 PRINCIPLES OF FEEDING FARM ANIMALS 



by special ferments in the intestinal tract of herbivorous animals. 

 By this decomposition marsh gas and other gases are formed, and 

 also organic acids, like acetic and butyric acids. Since straw is very 

 high in fiber, and ruminants, like steers, sheep, and goats, can sub- 

 sist for a long time on coarse straw only, we are justified in con- 

 cluding that this substance possesses a certain nutritive value, 

 although authorities differ as to how much value shall be ascribed 

 to the digestible portion of cellulose. 



Plants increase in their contents of fiber toward maturity as the 

 stems become coarse and tough; hence their digestibility decreases 

 during the latter stages of plant growth (p. 58). The following 

 approximate amounts of fiber are found in different classes of 

 feeding stuffs: 



Buckwheat hulls, buckwheat straw, and flax shives, 45 per cent; 

 straw of cereals, 40 per cent ; hay from different grasses or legumes, 

 20 to 35 per cent; cereals, 0.2 per cent (hulled rice) to 10.8 per cent 

 (oats) ; roots and tubers, 0.4 to 2.2 per cent; concentrated feeds, 0.9 

 to 30 per cent, generally, however, less than 20 per cent (Fig. 4). 



A high fiber content indicates that a feed is of relatively low 

 value for stock feeding, and vice versa. The figures for this com- 

 ponent, with those for protein and fat, are, therefore, of the great- 

 est assistance to feed buyers in judging the value of manufactured 

 and other feeds. 



Chemical Analyses of Feeding Stuffs. — The following com- 

 ponents are determined by the chemist in the ordinary analysis of 

 feeding stuffs: Water (often called moisture), protein, fat, fiber, 

 and ash; the difference between 100 and the sum of percentages 

 of these various components obtained in the analysis is known as 

 nitrogen-free extract (starch, sugar, pentosans, organic acids, etc.). 



Methods of Chemical Analysis. — The outline of the common method 

 adopted in chemical laboratories in the analysis of feeding stuffs given below 

 will be of value to students by enabling them to better understand data 

 and discussions relating to the chemical composition of feeding stuffs 

 (Fig. 5). 



a. Moisture (water) is determined by heating a small portion (gener- 

 ally 2 grams') 1 of the carefully-sampled and finely-divided feeding stuff 

 in a steam-bath or water oven at 100° C. for two to five hours, till it no 

 longer loses weight. After cooling in a desiccator, it is weighed carefully 

 on a chemical balance and the percentage loss calculated on the original 

 weight is taken to represent moisture. Volatile organic substances some- 

 times present in minute amounts in plant materials would also be in- 

 cluded in this loss. In the case of some feeding stuffs containing fats that 

 take up oxygen, as corn, flaxseed, and other oil-bearing seeds, the material 

 must be heated in a current of hydrogen or other inert gas, so as to 

 prevent oxidation and a resulting increase in weight during the drying, 

 which would give too low a moisture content. 



1 Jj of an ounce. 1 ounce equals 28.35 grams. 



