THE FEEDING OF FARM STOCK. 7C'J 



Digestibility. 



A question of even greater importance than the selection of a properly 

 .balanced food, is the question of its digestibility. The digestibility of a. 

 food depends upon three principal factors — {a) the nature of the food 

 itseU ; i J>) the kind of food with which it is mixed; and (,c) the nature of 

 the animal. The variability ot all these factors, and the difficulty of deter- 

 mining accurately the digestibility of different foods, makes this a rather 

 intricate problem. 



An enormous amount of experimental work has been done in Europe 

 the Tinted States in determining the digestibility of the different 

 constituents in mixed foods fed to different animals. Some idea of the 

 differences shown may be judged from the fact that, for example, when 

 bullocks and sheep are fed on clover-hay, only about half the total amount 

 of nitrogenous matter present is digested by the animal, whereas 80 per 

 cent, is digested from brewer's grains. 



Again only about 20 per cent, of the fatty matter in hay is digested by 

 the animals, whereas practically the whole of the fatty matter in brewer's 

 grains is digestible. 



Ruminants, again, are able to digest and make use of quite half the 

 woody fibre contained in their food, owing to the more complete preparation 

 the food undergoes in their system, whereas animals such as the horse and 

 the sheep are only able to digest a very small proportion of cellulose. Then, 

 again, the degree of maturity of plants affects their digestibility. Accord- 

 ing to European experiments, when clover-hay is fed to oxen before flowering, 

 71 per cent, of the nitrogenous matter was found to be digestible, when fed 

 in full bloom the amount digested diminished to 65 per cent., and when 

 the blooming was over the percentage of nitrogenous matter digested by 

 -oxen was only 59 per cent. 



It will be seen from these examples that the important question of the 

 digestibility of foods becomes a very intricate one. The process of diges- 

 tion varies considerably with different animals, rendering necessary a 

 difference in their food. Briefly, it is as follows: — In all animals the food 

 during mastication is mixed thoroughly with saliva before being swallowed. 

 The flow of saliva is pretty considerable in most farm stock; the horse and 

 the ox secrete about 100 lb. in the course of the day. 



Besides mixing the food mechanically into a bolus suitable for swallowing, 

 the saliva contains a ferment which changes the starch into sugar, this 

 action continuing in the stomach. Passing into the stomach the food 

 receives the gastric juice, which is poured upon it. The gastric juice is 

 an acid liquid containing hydrochloric acid, rennet, and pepsin, and other 

 soluble ferments. The special function of the pepsin in this acid solution 

 is to convert the albuminoids into soluble substances easy of digestion. 



The stomachs of different animals vary considerably in size and function. 

 Ruminants have four distinct stomachs or compartments, the stomach of 

 the ox holding about 230 to 260 quarts, whilst the single stomach of the pig 

 holds only about 7 to 9 quarts, and that of the horse 17 to 19 quarts. 



In ruminants the action of the first three stomachs is preparatory to the 

 fourth, in which digestion occurs. The single stomach of non-ruminants 

 corresponds with the fourth stomach of ruminants. 



Passing into the small intestines, the food now receives throe other fluid 

 secretions, the bile, which is secreted by the liver ; the pancreatic juice, 

 secreted by the pancreas or sweetbread; and the so-called intestinal 

 secretion. 



The bile is an alkaline fluid, and its principal function is to render the fats 

 and oils soluble, converting them into glycerine and soaps. 



+ 54797 — - 1 !• 



